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UV] RESHKARCH University of the Virgin Islands Agricultural Experiment Station Volume 5, 1993 ~~ J » awe in 2 ws fie / go Pe ' AT eS \ é “h ‘i aa Rey a eect , Wk Ao —_ aes St A i Y BAN AD as om a ea i Ny “thee NG (iy # b << ene ¥ . aa? Ba, | al call / ‘- vy = *) a et Se we P ds x é uy Lux VY ‘ae a \ 4 “a, aie WP: ah) ¥ vy "sh — aa “ii “N\ ie aA - _ “yg oe a & # -_ ¥ In this issue: La “* Y Strategies for Reducing Papaya Disease y Y/Y Hair Sheep Performance in Native Pasture al. we ae iy _v¢ Desmanthus Forage Production (i -. / Improving Herb Production with Drip Irrigation Y/Y Tilapia Species for Cage Culture 1 Hair Sheep Performance in an Extensive, Native Pasture System: A Five Year Summary Stephan Wildeus and Joni R. Collins 4 sustainable Strategies for Reducing Papaya Disease Problems in the U.S. Virgin Islands Christopher Ramcharan 6 Desmanthus, a Legume for Forage Production in the Caribbean Martin B. Adjei 9 Improving Culinary Herb Production with Drip Irrigation in the Virgin Islands Manuel C. Palada, Stafford M.A. Crossman and Charles D. Collingwood 13 Comparison of Tilapia Species for Cage Culture in the Virgin Islands James E. Rakocy, John A. Hargreaves and Donald S. Bailey 18 AES Personnel 19 Current Research Projects 19 Recent Publications Orville Kean, President, University of the Virgin Islands Darshan S. Padda, Vice President for Research and Land-Grant Affairs and Experiment Station Director James E. Rakocy, Associate Director Robin Sterns, Editor UVI Research is published annually by the University of the Virgin Islands Agricultural Experiment Station, RR 2, Box 10,000, Kingshill, St. Croix, USVI, 00850. Contents of this publication constitute public property. The written material may be reprinted if no endorsement of a commercial product is stated or implied. Please credit the authors, the University of the Virgin Islands Agricultural Experiment Station and UV] Research. To avoid overuse of technical terms, trade names of products are occasionally used. No endorsement of these products or firms is intended, nor is criticism implied of those not mentioned. The University of the Virgin Islands is committed to the policy that all persons shall have equal access to its programs, facilities and employment without regard to race, religion, color, sex, national origin, age or veteran status. Hair Sheep Performance In an Extensive, Native Pasture system: A Five Year Summary Stephan Wildeus and Joni R. Collins The most likely production environment encountered by hair sheep in the Caribbean region is that of a low-input, small scale farming system. Under these conditions, nutrition, management and a lack of genetic diversity become the major constraints to efficient production. In order for an animal to be productive in this type of environment it must successfully cope with these constraints. However, very little research data are available on the productivity of hair sheep under Caribbean conditions and how factors such as ewe age and season affect animal performance. | Among the objectives of the Sheep Research Facility at the Agricultural Experiment Station of the University of the Virgin Islands is to evaluate the production potential of the local hair sheep under a management system typically experienced by these animals. To this end, animals were grazed rotationally on native pasture (grass/ legume association) without supplementation. The rate of rotation was based on forage availability. All animals were also confined overnight to control predation and larceny. Ewes lambed without help on pasture and were provided no assistance in mothering up. Anthelmintics were administered routinely at two-month intervals. Modifications to the traditional system included controlled breeding and weaning (nine weeks after lambing) to facilitate data collection and analysis. The breeding system was based on an eight-month lambing cycle with ewes divided into an A and B flock, bred four months apart in a 34- day single sire mating period. Ewe body weights were recorded at weekly intervals, while lamb weights were recorded within 24 hours of birth and ‘at weaning (6344 days postpartum). Under this standardized management system, data were collected over a five-year period (1986-1990). Data (390 records) were analyzed with a statistical model that included year, season of year, parity, 1 litter size and flock as main effects. Parity was assigned into five categories (1st lambing, 2nd lambing, 3rd lambing, 4th-9th lambing and 10th- 12th lambing). Season of year was divided into the periods of January to April, May to August and September to December, with lambing concentrated in February/March, June/ July and October/November. Litter size was classified as single and multiple types of birth. ‘¢ Under Caribbean conditions, nutrition, management and a lack of genetic diversity are the major constraints to efficient production.7” There were significant differences in ewe and litter weaning weights between years (Table 1). The most pronounced change occurred from the first to the second year of the study with a general decline in ewe weaning performance. This reduction is most likely the result of a change in age structure of the flock, which started as a foundation flock of mature stock Table 1. Variations between years in ewe body weight and lamb production in hair sheep ewes on St Crokx. Table 2. Variations between seasons in ewe body weight and lamb production in hair sheep ewes on St. Cro. Criteria Year Criteria Season of Year 1 2 3 4 5 Jan-Apr | May-Aug | Sep-Dec Ewe breeding wt. (Ib) 77.4 | 80.0 | 83.3 | 76.7 |84.0 Ewe breeding wt. (Ib) 76.5 81.6 84.2 Ewe weaning wt. (Ib) 86.6 |77.6 |78.5 | 76.9 |79.4 Ewe weaning wt. (Ib) 18.7 86.2 81.4 Lambs born/ewe lambing 1.75| 163] 1.60) 1.60) 1.77 Lambs born/ewe lambing 1.65 1.66 1.69 Litter birth wt. (Ib) 11.5 |}108 |10.4 |10.6 /|11.2 Litter birth wt. (Ib) 10.5 TH? 10.9 Lamb survival to weaning (%)| 85.5 | 87.8 | 88.9 | 86.2 |80.6 Lamb survival to weaning (%) 87.1 85.9 fr Litter weaning wt. (Ib) 45.7 | 34.8 | 36.4 |39.9 |43.7 Litter weaning wt. (Ib) 39.0 40.3 34.2 recruited from a number oflocal farms reduced by 10% in lambs during weaning increased gradually into which younger replacement animals were entered in subsequent years. The younger replacement ewes had not reached mature production potential at this point. In the fifth year of the study ewe weaning performance had again reached first year levels and may suggest an overall improvement in flock performance as a result of selection and/or changes in native pasture quality through rotational grazing. Season of year had a significant impact on ewe performance at weaning, but not at lambing (Table 2). Ewe body weights were lower during the period of January to April compared to the other two seasons. In contrast, survival to weaning was September to December, compared to the remaining two seasons. The reduced lamb survival resulted in a decrease in litter size at weaning, from 1.45 lambs weaned/ewe lambing during January to April and May to August, to 1.31 lambs weaned/ewe lambing in September to December, and decreased litter weaning weight by 5-6 lb. The September to December period generally experiences increased rainfall and is associated with wet and muddy conditions, which appears to be the primary cause of the poor lamb survival, despite the availability of lush pastures. Ewe performance in relation to parity is summarized in Table 3. Ewe body weight at both breeding and throughout first to fourth parity and remained stable thereafter. Ewe body weight at weaning tended to decrease in the older ewes following the ninth parturition. Changes in litter size and litter birth weight with increasing parity mirrored those of ewe weaning weights, with the number of lambs born/ewe lambing increasing from 1.32 at first parturition to 1.83 at a mature level and litter birth weight increasing from 7.8 to 12.4 lb for the same stages. Again, there was a decline in litter size and birth weight as the ewes exceeded their ninth parturition. The increase in litter size at birth with increasing parity is reflected in the incidence of multiple births (Figure 1), shifting from a frequency of 70% single lambs Figure 1. The effect of parity on the distribution of birth type in hair sheep ewes on St. Crojx. 110 Figure 2. Ewe body weight at breeding and subsequent litter weaning weight in ewes giving birth to singles, twins and triplets. 100F ¢ ao ~ oO Oo | 1 % of birth type is oO | 30 -- 4-9th 3rd Parity 2nd 1st 100 Singles Twins 80 |- Triplets Weight (Ib) Oo) © b oO Ewe wt. Litter total weaning wt. 20 Single 10-12th Twin Triplet Type of Birth Table 3. Effect of parity on ewe body weight and lamb production in hair sheep ewes on St. Croix Criteria Parity ist | 2nd | 3rd | 4th | Sth Ewe breeding wt. (Ib) 65.3 |74.7 | 81.6 | 87.7 | 87.5 Ewe weaning wt. (Ib) 71.2 177.6 | 81.6 | 87.7 | 85.3 Lambs born/ewe lambing 1.32} 1.56 | 1.69] 1.83} 1.60 Litter birth wt. (Ib) 7.8 {10.0 | 10.7 | 12.4 | 10.7 Lamb sumval to weaning (%)| 86.6 {82.8 | 87.1 | 81.6 | 73.3 Litter weaning wt. (Ib) 32.0 37.0 40.8 | 39.7 | 28.4 at first parity to 29% in mature ewes. The corresponding increase in multiple births in the mature ewes was made up of 53% twin and 12% triplet births. No triplet births were recorded in ewes that exceeded their 9th parturition. Parity in the younger and mature ewes had no effect on lamb survival to weaning which ranged from 82 to 87% (mean 84.5%). However, lamb survival declined by 11% from this mean in the older ewes exceeding nine parturitions. This decline in lamb survival in the older ewes is also reflected in a litter weaning weight 11.5 Ib lower than that of mature ewes. Mature ewe weaning performance was achieved with third parity (Table 3). Ewe body weight at time of breeding had a significant effect on subsequent litter size (Figure 2). To a large degree this effect would be an indirect result of changes in age and parity, particularly in the case of single vs. multiple litters. However, differences in ewe body weight at breeding between twin-bearing ewes (85.3 lb) compared to triplet- bearing ewes (92.3 lb) may indicate a direct effect of body weight/condition on ovulation rate and subsequently litter size. There was a positive relationship between litter size and litter weaning weight (Figure 2), but differences between single and twin litters were more pronounced (11.6 Ib) than between twin and triplet litters (2.9 Ib). In contrast, other research at this station indicated that short term supplementation immediately prior to breeding (“flushing”) had no effect on ovulation rate in hair sheep under these production conditions. The average ewe body weight at breeding and weaning was 81 and 82 lb, respectively, when accounting for differences in year, season of year and parity structure of the flock. Similarly, overall flock lambing performance was 1.67 lambs born/ewe lambing, with an average litter birth weight of 10.8 lb. Average ewe weaning performance was 1.40 lambs weaned/ewe lambing, with a total litter weaning weight of 40.2 Ib. The litter size at weaning reflected a lamb survival of 83.7% from birth to weaning, with approximately 4-5% of these lambs born dead and the remainder dying during the period between birth and weaning. The overall productivity of the flock was high, considering the limited nutritional and managerial input, and ewes weaned approximately 50% of their body weight at breeding at nine weeks postpartum. The data further indicate that ewes reached their mature production potential following their third parturition and that productivity declined after ten parturitions. The latter would be linked to the relatively harsh production environment and the short lambing interval of eight months, although other data from this station indicate that the ewes resume cyclic activity within one to two months postpartum and thus reproductively support this production system. There was very little evidence of seasonal effects on productivity of the flock with the exception of poor lamb survival to weaning during wet season conditions. Ovulation rate and rebreeding were not affected by season, which is known to influence the performance of sheep under more temperate production environments. Subsequent work at this station has indicated some seasonal effects on the onset of puberty and the length of the postpartum interval in hair sheep under the environmental conditions on St. Croix, but these would not be expressed under the production system applied here. The authors would like to thank Victor Callas, Jr., Allan Schuster and Kim Traugott for their assistance in the collection of the data. This research was supported in part by the U.S. Department of Agriculture under Hatch Grant No. 787. Sustainable Strategies for Reducing Papaya Disease Problems in the U.S. Virgin Islands Christopher Ramcharan In the U.S. Virgin Islands, papaya (Carica papaya L.) is a unique tropical fruit with good domestic and export market potential to the U.S. mainland, Canada, Europe and Japan. Excellent potential for development exists locally with an expanding tourist market. There is also a certain amount of versatility in the use of papaya. Besides consumption as a fresh fruit, several processed papaya products can be developed, and papayas are used in both the ripe and green forms in various ethnic cuisines. Since the early 1960s when a small but ambitious program for the production and export of papaya was initiated on St. Croix, disease problems have decimated production and inhibited export of the fruit. This early program, however, was based solely on ' vn i i ! i GUANICA 2-1 the Hawaiian Solo cultivar, which performs well only within a narrow ecological niche. Major Disease Problems The two primary diseases affecting papaya in the U.S.V.I. are Papaya Ringspot Virus (PRV) and Bacterial Stem Canker (BSC). While the former is probably of worldwide importance, BSC has been identified only in certain regions, most of which possess climatic and soil conditions similar to those on St. Croix. For example, while BSC is prevalent on islands like Antigua which have agroecosystems similar to St. Croix’s, the disease never occurs in papaya plants of the geographically closer but ecologically different island of Puerto Rico. Soil type and rainfall _ patterns of Puerto Rico differ greatly from St. Croix’s, without the consequent environmental stress conditions. Infected plants are characterized by oily translucent spots or lesions on leaf petioles or stem of the top third of the plant. These enlarge or coalesce to form a stem canker, weakening the stem which may eventually become decapitated. The incidence of BSC also appears to be stress-related, particularly drought and soil-nutrient stresses, with certain cultivars such as the Hawaiian Solo being more susceptible than the Barbados Solo. The combination of water stress and high soil pH-induced nutrient deficiencies also make otherwise resistant cultivars susceptible to BSC. Papaya Ringspot Virus is a more ubiquitous disease problem and occurs 4 CRIOLLA PALAU ppg ite in ecosystems as diverse as those in the Hawaiian islands to those in the U.S. Virgin Islands. The major cause for this widespread incidence is that PRV is aphid-transmitted by the vector Aphis gossypii. Several other agricultural crop species, notably the cucurbits, are hosts for PRV. The symptoms caused by PRV include mottled and distorted leaves, ring spots on the fruit, and water-soaked streaks on stems and petioles. Unlike BSC, the PRV-infected papaya plant can often withstand or sometimes even outgrow the effects of the virus, depending on cultivar and plant vigor (Cariflora cv. is an example). In most cultivars, however, infected plants have an unhealthy appearance, gradually decline and produce infected and blemished fruits with drastically reduced market value. While one or two harvests can sometimes be obtained from PRV-infected plants, BSC usually terminates all production and results in stem collapse and death of the plant. Control Strategies In-depth research at UVI-AES in 1985-86 elucidated an Erwina sp. of bacteria as the pathogen causing BSC. Succulent-stem type cultivars such as the Hawaii Sunrise Solo, when cultivated under dry, windy and high pH soil conditions, become easy targets for this pathogen (cultivars such as the Barbados Solo with a more woody stem exhibit greater tolerance to BSC by usually outgrowing initial leaf or stem infections). Under these environmental stress conditions, cellular and plant tissue breakdown of succulent cultivars Table 1. Evaluation and rating of selected papaya cultivars under an integrated production system. Cultivar PRV' BSC' High Fruit Comments* pH' bearing? Cariflora R T T E Early low-bearing, short SL, good processing potential. Criolla R T T L Tall, late-bearing, large non-uniform fruits, good SL. Guanica S$ T T M_ Drought tolerant, prolific, pear-shaped, pink-fleshed fruit. PR6-65 FT T T M_ Pear-shaped, yellow- fleshed firm fruit, good SL. PR6-65 X T T T M_ Pink-fleshed, both Cariflora ovoid and elongate fruits, good SL. Solo SR X FT T T M Solo-shaped, pink- Cariflora fleshed, prolific. S-64 S T T E Low-bearing, very large pear-shaped fruit, few seeds. Barbados FT T T M Pear-shaped firm Solo fruit, good SL. Palau S S S M Small, elongate firm orange-fleshed fruit. ed . R = Resistant; T = Tolerant; FT = Fairly tolerant; S = Susceptible. 2. E = Early; M = Medium; L = Late. 3. SL = Shelf Life. occur more easily and rapidly, thus facilitating bacterial entry and infection. Research conducted by UVI-AES in 1986 on container- grown papaya plants under greenhouse conditions demonstrated conclusively that bacterial infections occurred only when Erwina inoculum was sprayed onto bruised leaves. This clearly indicated that plant injury, whether physically or physiologically induced, was essential for the bacterial infection causing BSC in papaya. Field trials conducted during the same years indicated that polyculture or intercropping papaya with other crops, such as pigeon pea, banana and cassava, significantly reduced disease incidence. More recent studies initiated in 1989 involving intercropped banana and papaya cultivars adapted to local soil and climatic conditions have shown no incidence of BSC. Intercropping with plantain and the use of Moringa (horse radish tree) windbreaks have also delayed and reduced the incidence of PRV. These two sustainable cultural practices apparently act by reducing actual wind-induced physical damage to plants, filtering off bacterial inoculum and deterring the buildup of virus-carrying aphids. These are in addition to the physiological advantages of reducing ambient moisture stress, thus decreasing excessive transpirational water loss in papaya plants and increasing water use efficiency. In a broad-leaved plant such as papaya, this is critical to maintaining turgidity in leaves and essential for reducing stomatal resistance and increasing photosynthetic activity. An ongoing UVI-AES trial with ten papaya cultivars for evaluating production methods has incorporated even more sustainable cultural practices, including minumum tillage, a permanent orchard sod cover, judicious use of herbicides and Leucaena and Moringa windbreaks. After almost four years of continuous production, no papaya trees have been lost to BSC, and only in the last year has there been a gradual buildup of PRV infection. The cultivars with the best overall performance under such an integrated system are included in Table 1. While a system of intercropping with the use of windbreaks and integration of certain cultural practices has virtually eliminated the incidence of BSC in papaya in the U.S.V.I. (Table 1), PRV continues to be a major problem. The selection, breeding and evaluation of virus-tolerant cultivars will continue to be major strategies for controlling PRV. Recently, biotechnology has been used to genetically engineer virus-resistant plants to the Hawaiian strain of PRV. This offers an exciting new phase in plant protection, and, to this end, the recently established biotechnology laboratory at UVI-AES has as one of its major objectives to genetically engineer papaya plants with resistance to the Caribbean strain of PRV. This research was funded in part by Hatch Project No. 0156331. Table 1. Desmanthus virgatus accessions subjected to clipping defoliation on St. Croix (1990-92). Vl accession Origin number st. Croix Venezuela Venezuela Venezuela Venezuela Venezuela Venezuela St. Croix Dominican Republic Dominican Republic Dominican Republic Dominican Republic Dominican Republic Dominican Republic Dominican Republic St. Croix Antigua Venezuela Venezuela Venezuela Mexico (CPI 92802) Mexico (CPI 92803) St. Croix Desmanthnus, a Legume for Forage Production in the Caribbean Martin B. Adjet In the Caribbean, predominant tropical grasses such as guinea grass (Panicum maximum) produce large quantities of biomass that are usually low in protein. Investments in fertilizer, especially N, P, and K, can help improve the protein status of tropical grasses. However, tropical grasses seldom exceed 10-12% protein levels, and these levels usually occur at young physiological ages when yields are very low. Confined livestock feeding operations, dairies and feedlots within the region need feed stuff that is high in protein. This need would be reduced if high-yielding legumes adapted to the environment were selected. The genus Desmanthus, of the Leguminosae subfamily Mimosoideae, includes tropical species with a center of origin in the Caribbean basin. Ecotypes range from 2 m high D. virgatus shrubs to the prostrate D. depressus. They are adapted to alkaline clay soils and occur naturally on many Caribbean grassland sites where they contribute to the diets of grazing livestock. Desmanthus is characterized by bipinnate leaves with leaflets less than 10 mm in length. Although in the same subfamily of legumes as Leucaena, Desmanthus is a much smaller plant with very little aggressive tendency to invade and dominate an 6 entire pasture. Progress is being made in the selection of Desmanthus varieties with superior agronomic traits for forage production at the Virgin Islands Agricultural Experimental Station on St. Croix. The initial screening of Desmanthus for their forage potential on St. Croix began in 1988. It included 35 collections of two species (D. virgatus and D. depressus) representing a wide range in area of origin and growth habit. Seedlings were transplanted on 1 m centers and evaluated as spaced plants. Although most accessions grew vigorously prior to defoliation, only five accessions continued to maintain vigorous growth following five successive harvests at 90-day intervals. In 1989, growth from the initial planting was accumulated and subjected to mob-grazing three times (April, mid- July and late October) to gauge their acceptability to sheep and response to grazing. Herbage of the erect accessions near shoulder high was grazed first. Prostrate accessions were grazed later. Animals readily and selectively grazed leaves, immature stems and green pods. “6 Results obtained so far indicate Desmanthus to be an outstanding forage crop with good quality when grown under natural Caribbean conditions. 7” Two accessions—VI 26 (also identified as CPI 92802 or CF 495) and VI 27 (CPI 92803 or CF 543), both originating from the Yucatan of Mexico—were superior in initial growth rating, herbage yield and final persistence. Accessions VI 26 and VI 27 were also the most vigorous following grazing. From May, 1990, to March, 1992, plots of 23 Desmanthus virgatus accessions (Table 1), established from reseeding of the original planting, were further subjected to prolonged clipping Figure 1. Mean annual total dry matter and edible dry leaf yields of Desmanthus accessions from three harvests on St. Crok (1990-92). St. Crom. Figure 2. Canopy ground coverage on 2 m* plots of Desmanthus accessions at the final (March, 1992) of six successive harvests on 15 14 (MilLeaf fraction 13+ (_JStem fraction 12} a 11+ 10 LJ LJ qT LJ DRY MATTER YIELD, T/HA Of NW AOS =~ oc oO a 123 45 6 7 9 1112 1415 16 17 18 20 22 23 24 25 26 27 28 VI ACCESSION # management to evaluate their forage yield potential, forage quality and stand persistence. This study was conducted on Fredensborg silty clay loam which had a pH of 7.8. There were three replicates of each entry arranged in a randomized complete block design. As ‘a low-input trial, plots were neither irrigated nor fertilized. Six successive harvests (three per year) were removed from plots (1 m x 2 m) whenever the median of all accessions attained the early-pod stage of maturity. Harvested subsamples were separated into leaf (including young stems and green pods) and stem components, dried and weighed. Selected accessions were analyzed for crude protein (CP) and in vitro organic matter digestibility | 5 CANOPY COVER, % 120 1107 100+ 90 + 80 - 70r 60+ S0F 40 30 10+ 0 (IVOMD). Prior to the final harvest in March, 1992, the canopy groundcover for each plot was estimated with a divided 1 m quadrat (100 divisions). Accessions differed significantly in total dry biomass and edible leaf forage yield (Figure 1). Three accessions (VI 6, VI 7 and VI 23), onginating from Venezuela, had the highest mean annual dry, leafy forage yield of 4-5 tons/ha. Most of the remaining accessions produced 3 tons/ha leafy forage, yearly, except for VI 11 which yielded less than 2 tons/ha. However, the two earlier selections from the Yucatan of Mexico, VI 26 and VI 27, were among the most persistent entries as determined by canopy ground coverage of approximately 95% at the final harvest “ inf eer cl : ade Hite je Tiga : 1 ji Hi fil ia || alt | ‘eal! ANTE DAF Fl i wh yon Hele erl tg ill i geal ah bale bay ape Fal: cay ‘ ay ae i} 123 45 6 7 9 1112 1415 16 17 18 20 22 23 24 25 26 2/7 28 VI ACCESSION # (Figure 2). Crude protein content of Desmanthus leaves was consistently high, ranging from 18 to 21% of dry matter (Figure 3). However, crude protein content of stems averaged only 8%. This suggests a necessity to select and manage Desmanthus forage crop for a higher leafy component in future studies. The leaf IVOMD of all accessions evaluated was above 80% (Figure 4). The data indicate the possibility to select accessions with a potential production of 3 to 5 tons/ha dry, edible leafy forage annually, when Desmanthus is harvested at the early pod stage of maturity. Such forage should be highly nutritious to livestock, containing approximately 20% CP and 80% IVOMD. The results obtained so far on Desmanthus indicate it to be an outstanding forage crop with good quality when grown under natural Caribbean conditions. Our preliminary feeding trials also suggest a more favorable hair sheep growth response to diets derived from grass/Desmanthus combination than from grass alone. Desmanthus is readily established from seed that is commercially available at the Caribbean Agricultural Research & Development Institute (CARDI) in Antigua. The initial seed multiplication by CARDI was contracted jointly by the University of the Virgin Islands and University of Florida with Desmanthus selections from St. Croix. Hard- seededness is a characteristic of the genus. The outcome of evaluation of methods of scarification on St. Croix is Figure 3. Crude protein as a percentage of dry matter in stems and leaves Figure 4. /n vitro organic matter digestibility of stems and leaves of of Desmanthus accessions on St. Croix (1990-92). Desmanthus accessions on St. Crox (1990-92). 25 100 —______-—_ & M§leaf [Stem - M@Leaf CJStem < : Zz 70 8 15h , ” 60} = = 50 = 10 S 40 ° P are “ 30 an | 20} Pe 10} O = = = — = = = = = = = = = = = —————— 2 04-2345 67 9 12 1415 16 17 18 22 23 24 2627 04-23 4 5 67 9 12 1415 16 1718 22 23 24 26 27 Vl ACCESSION # VI ACCESSION # that Desmanthus seed should be soaked in 70 °C water for one minute and then dried to improve germination. Planting should be done in well-prepared, moist seed bed at a seeding rate of 6 kg/ha. Good soil moisture availability during the initial two post-planting months ensures quick establishment and minimum weed problems. Three annual harvests at the early-pod stage of maturity are recommended for cut-and- carry forage management. Grazing management strategies for sustained Desmanthus pasture production are currently being investigated on St. Croix. A high level of interest in Desmanthus forage for alkaline, clay soils continues to be shown among researchers and graziers in tropical America, Australia and Africa. Present collections of Desmanthus in repositories include almost 300 accessions at CSIRO, Australia; over 150 accessions at CIAT, Colombia; and smaller collections at ILCA, Ethiopia; CARDI, Antigua; and the USDA. Recently, three cultivars were commercially released by Wright Stephenson Seed Co. of Queensland, Australia, at the 1993 International Grassland Congress. Clipping and grazing defoliation management information being generated by UVI- AES on St. Croix will contribute to Caribbean forage programs. This research was supported in part by the U.S. Department of Agriculture under Hatch Project No. 0220530. Improving Herb Production with Drip Irrigation In the Virgin Islands Manuel C. Palada, Stafford M.A. Crossman and Charles D. Collingwood Culinary herbs are important horticultural crops in the Virgin Islands. An informal survey conducted in 1988 revealed that sales of herbs and spices constitute a major source of income for many small-scale growers in St. Thomas and St. Croix. Herb production in the Virgin Islands mainly supplies the local market. A small percentage is exported to the U.S., while most of the herbs consumed in the U.S. are imported from the Mediterranean region, Africa and Latin America. Improving field production of herbs in the Virgin Islands will increase its potential for the export market and at the same time improve the local economy. Although most culinary herb species and varieties are easily adapted to the tropical climate of the Virgin Islands, field production is constrained by environmental factors and management a ewes EF . yeni = - J 7 1 Po 7... & I a a ® a 1 a ay 7 2% at i = = = a _. 7 . a "i a ™/- _* 7” we a i, a ee F i a - ai a #, ° Pw ae : =F eee i =z F ett - # ie. * * a = 7 , rm! Fr —— i m, " = , Sale ‘ a : ' a * 1 1 , tt if oageetin FRG 1 ji q m = FE a 7 & "ial Ly 5 ' ne i # i. 7 —— oo ae I. “tig a “ke ‘i te 7 r f ee al # : i pbs = = Se ae pe / iy “oe = a r mal 1 = re . . 5 =a, ps ied el — aim " * tts = eh tal tee ie = - a Fi " i r = = - i. ant e r Af practices. Water is a major limiting resource for agriculture in the Virgin Islands, and without supplemental irrigation, commercial production of high value crops such as herbs is not economically feasible. The traditional practice of growing herbs in the Virgin Islands requires frequent watering with sprinkler cans and garden hoses. This practice is inefficient and involves high labor and water use. Drip irrigation was first introduced to the Virgin Islands in the early 1980s. Studies at UVI-AES indicated that drip irrigation has more advantages compared to the traditional practice of supplying water to the crops, in terms of labor, water use, efficiency and cost. Many growers are now considering a drip irrigation system an essential component of their vegetable production enterprise. At UVI-AES, a research project was initiated in 1988 to improve field production of herbs through efficient water use and optimum fertilizer application. The application of drip irrigation technology was subsequently extended to herb production throughout the Virgin Islands. This report presents the results of drip irrigation experiments with basil (Ocimum basilicum) and thyme (Thymus vulgaris). Two field experiments were conducted to 1) determine the response of thyme to irrigation methods and rates and 2) determine the water requirements of thyme. In the first experiment, thyme seedlings were started in seedling trays and grown in the greenhouse in March, 1991. At 45 days after sowing, seedlings 9 were transplanted in field plots that were 9.4 feet long and 7.4 feet wide. Each plot contained three rows 30 inches apart. Seedlings were planted at a spacing of 12 inches in the row. Irrigation treatments consisted of two methods (drip versus micro- sprinkler) and two rates based on pan evaporation (40% PE versus 60% PE). Pan evaporation is the amount of water that is lost through evaporation from a standard Class A circular pan measuring 46.5 inches in diameter and 10 inches deep. Half of the plots in treatment under drip irrigation were covered with | mil (0.025 mm) black plastic mulch. None of the plots under micro-sprinkler irrigation were mulched. The drip irrigation system consisted of main and submain lines made of 0.6-inch (15 mm) polyethylene hose, and the laterals were made of 0.6- inch (15 mm) drip strip with laser- drilled orifices 12 inches apart. The micro-sprinkler system consisted of 0.6-inch polyethylene hose with micro- sprinklers attached to the laterals in center rows. The experiment was arranged in a randomized complete block design with six treatments and three replications. The experiment was conducted from March to September, 199]. Data presented in Table | show that under drip irrigation, fresh yield of thyme in plots without plastic mulch was higher than with mulch. The difference in yield between the two rates of irrigation (40% PE vs. 60% PE) was not statistically significant either in mulch or no mulch Table 1. Yield of thyme under two methods and rates of irrigation. UVI-AES, 1990. Irrigation Irrigation Rate Mulch Fresh leaf yield’ system (% PE?) (t/ac) Drip 40 No 3.5/a Drip 40 Yes 1.34c Drip 60 No 3./5a Drip 60 Yes 2.32b¢C sprinkler 40 No 2.05bce Sprinkler 60 No 3.04ab Values within a column followed by the same letters are not significantly different by Duncan's Multiple Range Test, (P<0.05). “Pan evaporation. Table 2. Plant height, total plant fresh and dry matter yield of thyme grown at three levels of drip irrigation with and without mulch. UVI-AES, 1992. Irrigation Mulch Plant Plant Yield' level height’ Fresh Dry (cb) (in) (Ib/ac) (Ib/ac) 20 No 8.03a 4436a 1432a 40 No 7.87a 2647b 884b 60 No 7.60ab 3121b 1044ab 20 Yes 5.98b 2013bc 597bc 40 Yes 6.42ab 1799bc 571be 60 Yes 6.73ab 963c 296c Rainfed No 6.5/7ab 2479b 876b ‘Values within a column followed by the same letters are not significantly different by Duncan's Multiple Range Test, (P<0.05). Table 3. Estimated irrigation water use and efficiency of thyme at three levels of irrigation with and without mulch. UVI-AES, 1992. Irrigation level Mulch Total water use WUE!" (cb) (gal/pit) (ft?/ac) (lb/ft?) 20 No 1.55 7036 0.63 40 No 1.19 5406 0.49 60 No 0.48 2160 1.44 20 Yes 1:55 7036 0.29 40 Yes 1.19 5406 0.33 60 Yes 0.48 2160 0.45 Rainfed No 4.33? 19621? 0.13? 'WUE= water use efficiency in pounds dry matter per cu. ft. “Represents amount of rainfall based (1 inch rain = 27,000 gallons/acre). Table 4. Estimated cost of irrigation water and efficiency in thyme production with drip irrigation. UVI-AES, 1992. Irrigation Irrigation Returns to level Mulch water cost’ irr. water? (cb ) ($/ac) ($/$) 20 No 844 70.62 40 No 649 54.80 60 No 259 161.93 20 Yes 844 32.04 40 Yes 649 37.57 60 Yes 259 44.95 ‘Based on water cost of $0.12/cu.ft. “Dollar retum to every dollar spent in irrigation water. 10 treatment. Under micro-sprinkler irrigation, fresh yield of thyme at an irrigation rate of 60% PE was numerically higher than at 40% PE. However, the yield at 60% PE was similar with those obtained from drip-irrigated treatments without mulch. The lower yields from drip-irrigated plots with black plastic mulch and those under micro-sprinkler irrigation were attributed to the high incidence of fungal diseases. Wet soil in plots with plastic mulch and frequent wetting of foliage in sprinkler-irrigated plots may have contributed to favorable development of soil-borne fungus diseases including Phytophthora sp., Phythium sp., and Rhizoctonia solani. Results of this experiment indicate that improved yield of thyme was achieved under drip irrigation without mulch. This method has the added advantage of allowing growers to cultivate and mound the soil around the plant for better plant growth. The micro-sprinkler method is not only inefficient, but also requires high volumes of irrigation water since part of the water applied is lost through evaporation and spray drift. The second experiment was conducted to determine the irrigation water use and requirement of thyme with and without mulch. The treatments consisted of three irrigation levels corresponding to soil moisture tension of 20, 40 and 60 in centibars (cb). A centibar is a unit used to measure the amount of pressure by which the soil particles hold water or moisture. The higher the pressure the lower the amount of water or moisture available to plants. Soil moisture tension is measured by using a device called a soil tensiometer. Half of the plots were mulched using a black plastic, water- permeable weed barrier ground cover. A rainfed control (no mulch) was included as a treatment. Thyme seedlings were transplanted on March 20, 1992, in three-row plots arranged in a randomized complete block design with four replications. Plot size measured 3 feet x 8 feet. Plants were spaced 12 inches between rows and 8 inches between plants within rows. The plants were fertilized with nitrogen, phosphorus and potassium at the rate of 45, 90 and 90 Ib/ac, respectively. The fertilizer was applied one week after transplanting. The drip irrigation system installed in plots was similar to that in the first experiment. Soil tensiometers were installed at a 6-inch depth in each treatment on two replications to monitor soil moisture tension. The tensiometers were read daily and irrigation was turned on when readings were above a prescribed centibar treatment. A water meter and timer were also installed for each treatment. Data were collected on plant height at harvest, plant fresh weight yield and dry matter weight. Total irrigation water use was determined over a period of nine weeks. High rainfall during the growing season confounded the results of the trial. Over a period of three months (April to June) total rainfall was 13 inches (Figure 1). May was the wettest month with rainfall of 11 inches. Despite the high rainfall, differences in yield among treatments were significant (Table 2). Total plant fresh yield was highest (4436 Ib/ac) Figure 1. Rainfall and potential evapotranspiration at UVI-AES, Table 5. Plant fresh yield of drip-irrigated basil grown with organic 1992. and synthetic mulches. UVI-AES, 1991. 20 GB Rainfall, inches [— 7] Pan ET, inches Harvest Mulch 1st 2nd 3rd 4th Total (yield, t/ac)’ Compost 2.2 5.2 10.5a 104a 28.4a 10 F Grass straw 18 38 5.7b 82ab 19.6b Black plastic 2.5 5:3 92ab 7.1ab 24.2ab Weed barrier 2.4 5.0 6.2b 46b 18.3b Control (no mulch) 1.9 4.8 84ab 5.0b 20.3b Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec ‘Values within each column followed by the same letter are not significantly different by Duncan’s Multiple Range Test, (P<0.05). from the treatment with an irrigation regime maintained at 20 cb without mulch. Dry matter yield was also highest for this treatment, but not significantly different from the treatment under an irrigation regime of 60 cb. Generally, all treatments with mulch and the control (rainfed) had lower yields than irrigation treatments without mulch. This result is consistent with those obtained in the first experiment and would indicate that mulching is not beneficial for thyme. Furthermore, when soil moisture is not a limiting factor because of high rainfall, mulching is no longer an advantage. Total irrigation water use was highest in treatments with an irrigation regime of 20 cb (Table 3). Treatments under 60 cb had the least water use. However, only the treatment at 60 cb without mulch resulted in more efficient use of irrigation water at the least cost (Table 4). This result would suggest that under high rainfall, supplemental irrigation can be reduced by maintaining the soil moisture at 60 cb. At this level the minimum water requirement of thyme can be met. However, during seasons of low rainfall this level may change. Although thyme does not respond favorably to mulching as shown in the two experiments, integrating drip irrigation with mulching can further conserve water by reducing water use, evapotranspiration and weed control and _by increasing overall water use efficiency for other crops. The choice of mulching materials may also influence the response of herb species to drip irrigation. In the summer of 1991 an experiment was initiated to 1) determine the effect of various mulching materials on yield and water use of basil under drip irrigation and 2) compare water use efficiency of basil grown with organic and synthetic mulches. Basil was grown in plots with organic (compost or grass straw) and synthetic (black plastic or weed barrier ground cover) mulches. The compost was prepared using a 1:1 ratio of sheep manure and vegetable crop residues. The grass straw was made of dry pangola grass. The compost and grass straw mulches were applied at 2 inches thick. A control plot (no mulch) was also included as a treatment. Plot size was 4 feet x 7 feet with rows 16 inches apart. Plants were planted at 12 inches spacing within rows. The experiment was I We BF OE Wie he i. a jal et i = ee iL, th an elt he, HF iat i ! hey P| a a al "' “ - rk ' —— rl! lel aa aid cit oe oy ale iC “Mag i a 1 afl 4 ae f en ‘ eae : ru bal — r 4 = a = a = _ — oo | aol Oh ie i in ging re i ee ea ru -- i iain a F 4 eee sik ge Pi foenn | be eli. ut iy an ok ge aoe Hg f ie eee i, e. 11 arranged in a randomized complete block design with four replications. All plots were drip-irrigated to maintain soil moisture at 30 cb. The drip irrigation system installed was similar to that of the 1991 experiment on thyme. The amount of irrigation water used was monitored with water meters installed for each treatment. Data on Table 5 show that plant fresh yield did not vary significantly among treatments during the first and second harvests. Differences in yield were observed in the third and fourth harvests. At the third harvest, basil grown with compost mulch produced the highest yield of almost 10.5 t/ac. This was followed by plants with black plastic mulch and the control. Basil grown with grass straw and weed barrier ground cover produced lower yields. At the e Pe hai Ae ee ag - "hy, aa 1" a oe EB r Paar = 4 é : 4 is, laa i az + - no i ’ seer jer " te Ae — —s Table 6. Irrigation water use of basil grown with organic and synthetic mulches. UVI-AES, 1991. Mulch Total fresh yield Total water use WUE" (t/ac) (ft°/ac) (lb/ft?) Compost 28.4 22719 1.25 Grass straw 19.6 21091 0.93 Black plastic 24.2 24877 0.97 Weed barrier 18.3 18390 1.00 Control 20.3 21634 0.94 "WUE = water use efficiency (Ib fresh basil per cu. ft. water). Table 7. Yield and economic returns from drip-irrigated basil grown with organic and synthetic mulches. UVI-AES, 19971. Mulch Total yield Gross value’ Irr. water Returns to (t/ac) ($/acx1000) cost? irr. water® ($/ac) ($/$) Compost 28.4 113.6 2726 41.6 Grass straw 19.6 78.4 2531 31.0 Black plastic 24.2 96.8 2985 32.4 Weed barrier 18.3 faz 2207 33.2 Control 20.3 81.2 2596 34:3 'Fresh basil at $4.00/Ib. ‘irrigation water at $0.12/cu.ft. *Dollar return for every dollar spent on irrigation water. ¢¢Although basil grown with compost mulch used more water than other treatments, yield and water use efficiency were the highest, resulting in higher gross returns. 77 fourth harvest, basil grown with compost mulch maintained the highest yield. Total yields of basil grown with compost mulch were significantly higher than the other treatments with the exception of the black plastic mulch. Differences observed in plant fresh yield were also reflected in leaf fresh yields. The treatment with compost mulch produced the highest fresh leaf yield, followed by the treatment with black plastic mulch (Figure 2). Total water use was highest in plots with black plastic mulch (15% more than the control), followed by compost mulch which was 5% more than the control (Table 6). Grass straw and weed barrier ground cover reduced water use by 3 and 15%, respectively. The high water use in plots with black plastic mulch may be associated with high soil temperature (data not shown) which may have induced rapid loss of soil moisture. In compost-mulched plots large water use may be associated with high water absorbing capacity of compost material which acted like a sponge. Low imation water use in the control Figure 2. Fresh leaf yield of basil grown with organic and synthetic mulches. UVI-AES, 1991. 8 of Harvest (J ist br = 3rd © 5b 4th a 4h id Z 2 3 2 "4 Compost Straw _ Black Plastic Weed Barrier Control 12 plots can be explained by the addition of rainfall which totalled 13 inches during the five-month growing season (March to July). The higher yield from the treatment with compost mulch can be partly explained by possible leaching of nutrients from compost down to the root zone. During decomposition of compost materials, nutrients are released slowly and become available to plants. Nutrient contribution from the compost material may have increased towards the latter part of the growing season as shown by the higher yield of the final two harvests. Although basil grown with compost mulch used relatively more water than other treatments, yield and water use efficiency were also the highest. This resulted in higher gross returns and returns on irrigation water (Table 7). At a $4.00/ Ib wholesale price of fresh basil, treatment with compost mulch gave the highest gross return of $114,000/ac. If herb growers have to pay for irrigation water at $0.12/cu ft., using compost mulch will give them the highest returns on irrigation water of $42 for every dollar spent. This study has shown that compost mulch increased basil yield, improved water use efficiency and boosted economic returns to irrigation water. Integrating compost mulch with drip irrigation for basil production offers some economic benefit for small-scale herb growers in the Virgin Islands. Organic mulches such as compost and grass straw are locally available, thus saving herb growers the cost of importing expensive synthetic mulches. The only drawback of using organic mulches is the potential weed problem associated with either compost or grass straw material. If the mulch is made from materials containing viable weed seeds, weed growth can be a problem. The results of experiments on thyme and basil also suggest that the response of herb species to mulching is variable. Basil responded favorably to mulching while thyme did not. Additional studies are being carried out at UVI-AES to investigate the response of other herb species to drip irrigation and mulching. This research was supported in part by Hatch Regional Project No. 247 and CBAG Project No. 472. Comparison of Tilapia Species for Cage Culture in the Virgin islands James E. Rakocy, John A. Hargreaves and Donald S. Bailey Tilapia is a tropical fish native to Africa and the Middle East. Since tilapia is a hardy fish that feeds low on the food chain and is relatively easy to culture, it has been distributed widely throughout tropical countries to increase protein supplies. Tilapia is also being cultured in many temperate countries in heated or geothermal water because its delicious taste and excellent nutritional qualities make it an attractive food item. At least 77 species of tilapia are found in the African continent, but only nine are considered to be suitable for aquaculture. These species differ in a number of important culture traits. For example, Oreochromis aureus is the most cold- tolerant (tilapia generally die at temperatures below. 50°F) while O. mossambicus 1s tolerant to high salinities. Aquaculturists have increased the diversity within tilapia genera by crossing species to create hybrids or through programs of selective breeding to develop new strains. Many new strains have resulted from accidental crossing (contamination) of pure species. Strains also develop naturally within a species when there is geological isolation. An example of significance to aquaculture is the occurrence of three distinct species of O. niloticus, the Ghana, Ivory Coast and Egypt strains, with varying culture characteristics such as cold tolerance and growth rate. One major breakthrough in the development of new strains was the appearance of a red mutant O. mossambicus in Taiwan in 1968. This single fish was crossed with O. niloticus to begin a strain of red tilapia, which led to a second wave of tilapia dispersal to tilapia-culturing countries where the red strain was crossed with other species to create new strains of red tilapia, some containing genes from as many as four species. Selective breeding of red tilapia strains has improved their appearance from an initial mottled look with blotches of dark wild color to a blend of red, orange, pink and white. Red tilapia now resemble colorful ocean fish such as red snapper, which increases their marketability. Wide variability among cultured tilapia species and strains causes uncertainty during stock selection. Farmers want stock that exhibit fast growth, high survival, efficient feed conversion, attractive coloration and good body conformation under actual culture conditions. Other desirable traits include resistance to disease, high dressing 13 percentage and high quality flesh. To aid perspective Virgin Islands fish farmers in selecting the best available stock, two species comparison experiments were conducted at the University of the Virgin Islands Agricultural Experiment Station (UVI-AES). In experiment 1, the performance of O. niloticus, O. aureus and three strains of red tilapia were evaluated in freshwater cages. In experiment 2, the performance of O. mossambicus and “Florida” red tilapia were evaluated in saltwater cages. In experiment 1, tilapia stocks came from the following sources: 1) Oreochromis niloticus (Ivory Coast strain). The stock of O. niloticus originated in West Africa and was shipped to Auburn University via Brazil in 1974. Fish were subsequently shipped from Auburn University to the Tennessee Valley Authority in Muscle Shoals, Alabama, and from there to UVI-AES in 1981. 2) Oreochromis aureus, The stock of O. aureus originated in Israel from which fish were shipped to Auburn University in 1957. Fish were subsequently shipped from Auburn University to the University of Puerto Rico, Mayaguez, and from there to UVI-AES in 1974. 3) “Florida” red tilapia (FRT). FRT was developed in the late 1970s at Natural Systems in Palmetto, Florida, by crossing wild (black) O. urolepis Figure 1. Average growth rate of O. niloticus, O. aureus, and “Florida,” "Aurea" and "Taiwan" red tilapia cultured in 1-m3 cages for 143 days. — g600b TILAPIA GROUP i o | o—o OQ. niloticus _ _ = 500+ o—o O. aureus ZA ii ~ - a—a FRT fl + 400- =—s ART = © - e—e TRT 7 rie i 300+ 4 = 3007 | ty 6.2004 ud w 100 L a F 0 —ESEE Ee Lefpy yy yyy p43 0 4 8 12 16 20 WEEKS hornorum females with red O. mossambicus males to produce F, (first generation) hybrids exhibiting variable skin coloration ranging from white to red/orange with melanistic (black) mottling. After an extensive selective breeding program, initially at South Florida Fisheries in Lantana, Florida, and later by Sunfish Hatcheries in Jamaica, F,. or F,, fish were obtained by UVI-AES in 1986 from the Jamaican hatchery and used in experiment I. 4) “Aurea” red tilapia (ART). Male F, “Florida” red hybrids (O. urolepis hornorum X O. mossambicus) were crossed with female O. niloticus and female O. aureus in the early 1980s at Tennessee Valley Authority. The red progeny of these crosses were crossed again to form a “four-way line” containing 25% of the genetic material of each of the parent species. South Florida Fisheries crossed wild O. aureus females with four-way line males to produce F, ART. This process was repeated until an F, ART was obtained that consisted of 95% O. aureus heritage. UVI-AES received F, ART from Sunfish Hatcheries in 1986 and used them in experiment 1. 5) “Taiwan” red tilapia (TRT). This strain was developed in Taiwan from 1968-1972 by crossing red female O. mossambicus with male O. niloticus. In 1983, the University of Puerto Rico provided UVI- AES with TRT which were derived from a founder stock of 40 fish from Panama. The freshwater cage culture study was conducted in Chimney Bush pond, a five- acre watershed pond on St. Croix, in 1-m° (35ft?) cages. The cages were 3.5 feet in diameter, four feet deep and made from semi-rigid plastic screen with 0.75-inch mesh. The cages were individually anchored to concrete blocks and placed in six rows of five cages each. The rows of cages were perpendicular to the pond bank and roughly parallel with the prevailing wind direction (east, northeast). Cages were placed approximately six feet apart within rows and 20 feet apart between rows. A demand (self) feeder was secured to the top of each cage. The feeders were checked every day at 10:00 a.m. and 3:00 p.m. and refilled when empty with 12 lb of floating, pelleted feed containing a nutritionally-complete diet (36% protein, Purina #5144). 14 The fingerlings in this study were fed a male sex hormone as fry to convert the female fry to males. Sex-reversed male fingerlings of each tilapia group were stocked at a rate of 300 fish per cage into six cages. Tilapia groups were assigned to cages according to a randomized complete block design with each row of cages representing a block. Three of the 30 cages were lost during the experiment due to the theft of one cage from each red strain. At intervals of 28 feeding days, approximately 20% of the fish from each cage were weighed, counted and returned to the cage. The experiment was terminated after 143 feeding days, at which time all of the fish were weighed and counted. During the harvest, ten fish were selected from each tilapia group and weighed individually to the nearest gram. Scales, gills and viscera were removed from each fish, which was then reweighed After removing the head, the carcass was weighed again to determine dressing percentage without head. Ten additional fish were selected from each tilapia group and weighed individually to the nearest gram. After scaling the fish, two fillets were excised from each fish and weighed. The fillets were reweighed following removal of the skin. The percentage of the fillet yield with and without skin was calculated. A gross proximate analysis of body composition was conducted on three individuals of each tilapia group. Moisture was determined by drying the fish in an oven. Crude protein was determined by Kjeldahl-sulfuric acid digestion. Lipid (fat) was determined by the modified Babcock method. Results of this study showed that O. niloticus was the fastest-growing species (3.77g/day) and grew to the largest size (616 g, 1.37 lbs.) within the 20-week culture period (Figure 1, Table 1). Among the red varieties, the “Florida” red tilapia grew at the highest rate (3.50 g/day) to the largest size (577 g, 1.27 lbs.). As cage biomass increased, growth rates declined for TRT after week 8, for O. aureus after week 12, and for FRT and ART after week 16 (Figure 1). Although O. niloticus grew at its highest rate from week 4 through 8, it continued to grow at a steady and substantial rate through week 20. Net production reflected the growth rate with O. niloticus ranking first and FRT ranking second (Table 2). Total production ranged from 119 kg (262 Ibs.)/m? (35 ft?) for O. aureus to 182 kg (400 Ibs.)/m? (35ft*) for O. niloticus. There was little difference in total production per cage between FRT (163 kg, 359 Ibs.) and ART (161 kg, 354 Ibs.). Survival ranged from 93.3% for FRT to 98.4% for O. aureus. The feed conversion ratio (FCR), calculated by dividing feed weight by fish weight gain, ranged from 1.29 for O. aureus to 1.68 for TRT (Table 2). This Table 1. Average initial and final body weight, daily weight gain and specific growth rate of O. niloticus, O. aureus and “Florida,” “Aurea,” and “Taiwan” red tilapia cultured in 1.0-m? cages for 143 days. Tilapia Number Initial Final Daily Specific group of cages body weight body weight weight gain growth rate (g/fish) (g/fish) (9) (%/day) O. niloticus 6 fac! 616a? 3.77a? 1.45a? O. aureus 6 77b 403d 2.28d 1.16d “Florida” red 5 70d 577b 3.50b 1.41ab “Aurea” red 5 83a 551b 3.31b 1.38b “Taiwan” red 5 85a 470c 2./5¢ 127°C ‘Average values within a column followed by the same letter are not significantly different (P>0.05) as determined by pairwise t-tests. 2These average values are “least square means,” the values that would have occurred if the initial body weights were equal. Table 2. Average initial and final fish biomass, net production, feed conversion ratio and survival rate of O. niloticus, O. aureus and “Florida,” “Aurea,” and “Taiwan” red tilapia cultured in 1.0-m* cages for 143 days. Tilapia Number _ Initial Final Net Feed Survival group of cages biomass biomass production conversion rate (kg/m3) (kg/m3) (kKg/m3) ratio (%) O. niloticus 6 22¢c" 182a? 159a? 1.30c? 97.7a*° O. aureus 6 23b 119¢ 96c 1.29c 98.4a “Florida” red 5 21d 163b 140b 1.45b 93.3b “Aurea” red 5 25a 161b 138b 1.31be 98.3a “Taiwan” red 5 25a 132c 109c 1.68a 94 9ab ‘Average values within a column followed by the same letter are not significantly different (P>0.05) as determined by pairwise t-tests. ?These average values are “least square means,” the values that would have occurred if the initial body weights were equal. 3Survival growth rates were arcsine-transformed prior to analysis. Table 3. Average condition factor (K) and dressing percentage of O. niloticus, O. aureus and “Florida,” “Aurea,” and “Taiwan” red tilapia’. Tilapia K? Dressed Dressed Fillet Fillet group with head without head’ with skin without skin (%) (%) (‘%) (%) O. niloticus 3.11b* 85.6a‘ 65.6a‘ 39.0a‘ 33.4a‘ O. aureus 3.00c 85.2a 64.7a 38.4a 33.8a “Florida” red 3.21a 84.9a 64.0be 38.6ab 34.3a “Aurea” red 2.87d 85.6a 64.3ab 38.3a 33.5a “Taiwan” red 2.85d 86.0a 63.4c 36.4b 31.1b ' Ten individuals were analyzed from each group for dressing percentage with and without head; ten individuals were analyzed from each group for dressing percentage of fillet with and without skin. 2K = body weight (g) x 10°/total length (mm)’. 4Average values within a column followed by the same letter are not significantly different (P>0.05) as determined by pairwise t-tests. ‘These average values are “least square means,” the values that would have occurred if the initial body weights were equal to 456g for dressed with and without head and 571g for fillet with and without skin. All percentage data was arcsine-transformed prior to analysis. 15 Table 4. Average moisture, protein and lipid content of O. niloticus, O. aureus and “Florida,” “Aurea,” and “Taiwan” red tilapia’. Tilapia Moisture Protein Lipid group (%) (‘%) (%) O. niloticus 78.2a* 18.5cd 1.4b O. aureus 75.3¢ 21.0a 1.4b “Florida” red 76.4bce 20.1b 3.6a “Aurea” red 78.0ab 17,740 1.2b “Taiwan” red 78.5a 19.1¢c 1.2b 'Three individuals were analyzed from each group. 2Average values within a column followed by the same letter are not significantly different (P>0.05) as determined by pairwise t-tests. means that 1.29 lb of feed were required to produce a one-pound weight gain in O. niloticus compared to 1.68 lb of feed for a one-pound gain in TRT. The FCR values of O. niloticus (1.30) and ART (1.31) were exceptionally low for such large fish. The use of demand feeders appears to be a very efficient method of feeding caged tilapia. The FCR of FRT was numerically intermediate (1.45). The condition factor is a number that relates weight to length and indicates how robust (or emaciated) a fish is. FRT displayed the highest (best) condition factor (3.21), followed by O. niloticus (3.11) (Table 3). The lowest condition factors occurred among TRT (2.85) and ART (2.87). These strains were visibly thinner than the other tilapia groups, and approximately 15% of TRT exhibited some degree of caudal fin rot. The dressing percentage with head (scales, gills and viscera removed) was similar for all the tilapia groups, ranging from 84.9% for FRT to 86.0% for TRT (Table 3). With the removal of the head, some statistically significant changes occurred in the ranking. TRT displayed the lowest dressing percentage (63.4%), indicating that its head size was relatively large compared to its body, while O. niloticus exhibited the highest dressing percentage (65.6%), suggesting that its head size was relatively small. Small head size is a desirable trait because meat yield increases as head size decreases. This relationship was confirmed by the results of fillet yield with skin, which was lowest for TRT (36.4%) and highest for O. niloticus (39.0%). With the removal of skin, O. niloticus dropped to fourth in the ranking of fillet yield (33.4%), indicating that its skin may be thicker than the skin of the other tilapia groups. The fillet skin ranged from 4.3% (FRT) to 5.6% (O. niloticus) of total body weight. The differences in dressing percentages among the tilapia groups were relatively minor except for those of TRT, which were significantly lower in most categories. Gross proximate analysis of body composition revealed that from 75.3% (O. aureus) to 78.5% (TRT) of total body weight consisted of moisture (Table 4). Protein levels ranged from 17.7% (ART) to 21.0% (O. aureus). Lipid content, which was similar among four of the groups (1.2-1.4%), was significantly higher (3.6%) for FRT. Fat deposits were visible in the flesh of FRT and in a thick layer over the swim bladder. FRT registered the highest condition factor (Table 3), another indication that it was the fattest fish. FRT may require a restricted feeding regime or a diet with a lower energy-to-protein ratio to reduce fat content. The most nutritious species was O. aureus, which registered the lowest moisture content, the highest protein level and a moderate lipid level. By nearly all measures, the culture performance of O. niloticus was superior to the other tilapia groups. Dressing characteristics of O. niloticus were similar to or better than the other groups, although protein levels were comparatively low. If color is not a factor in marketing tilapia products, such as skinless fillets, O. niloticus is the best species for freshwater cage culture in the Virgin Islands. After 16 completing this study, UVI-AES replaced the Ivory Coast strain of O. niloticus with the Egypt strain, which grows faster according to a recent study. The other pure species in this study, O. aureus, grew ata low rate and should not be considered for culture, although all other growth and dressing characteristics were favorable. Marketing studies have shown that Virgin Islanders prefer red tilapia because they resemble brightly-colored ocean fish. Among the red strains, FRT performed best in most categories, except survival, feed conversion and fat content. ART performed nearly was well as FRT, and most of the differences between ART and FRT were not statistically significant. However, production of F, ART fingerlings involves the maintenance of separate breeding lines and is much more complicated than using a single FRT strain to generate seed stock. Since ART offers no clear growth or dressout advantage, FRT is the recommended strain of red tilapia for the Virgin Islands. TRT performed poorly in growth, feed conversion and meat yield and is therefore unsuitable for the Virgin Islands. In experiment 2, O. mossambicus were derived from stocks captured in the Salton Sea in California and transported to the University of Puerto Rico and from there to UVI-AES in 1988. FRT came from the same source as described in experiment 1. The study was conducted on St. Croix in Salt River Bay, a protected embayment which is open to the sea and receives freshwater runoff only during periods of intense rainfall. During the study, salinity ranged from 35 to 38 parts per thousand (ppt). ' Three cross-shaped rafts (wooden walkways) were anchored in approximately nine feet of water at a distance of 30 feet from a fringe of red mangrove in a small arm of the bay. Two 2-m? (70ft*?) cages were secured to each of the three rafts. The cages were constructed of galvanized mesh (0.75-inch) formed into a rectangular shape measuring five feet long by four feet wide by four feet deep. The mesh was treated with a blue antifoulmg paint contaiming tributyltin fluoride. A feeding ring was placed in each cage. Initially, 0.12- inch plastic mesh was tied to rubber inner tubes. Many inner tubes deflated due to degradation of the rubber by salt water and sunlight. These were replaced by encapsulated polystyrene rings measuring 16 inches (inner diameter) by 24 inches (outer diameter) by six inches (height). The same 0.12-inch plastic mesh was tied to the outside of the rings and extended 12 inches into the water. Sex-reversed male fingerlings of each tilapia group were stocked at a rate of 40 fish per cage (20 fish/m?, 35ft*) into three cages, one cage from each raft. The cages were stocked at low rates due to a shortage of fingerlings and the logistics of acclimating the fingerlings to seawater. The fingerlings had been raised in fresh water and were acclimated to seawater over a five-day period by direct transfer to aerated tanks of increasing salinity: 15 ppt (day 1), 20 ppt (day 2), 25 ppt (day 3), 30 ppt (day 4), and 35 ppt (day 5). The fish were fed a floating, nutritionally complete diet (36% protein, Purina #5144) at 3.0% of body weight daily once per day in the moming. The feeding rate was adjusted weekly based on an assumed feed conversion ratio of 2. The fish were not sampled during the experiment to avoid injury and subsequent infection, as tilapia are not as resistant to disease in full-strength seawater as they are in fresh water. After 50 feeding days, the fish began to show signs of bacterial infection which led to low rates of mortality. After 64 days, feed treated with oxytetracycline (Terramycin) was offered to the fish at a rate of 80 mg/kg of fish body weight for 14 days. Fish resumed active feeding following treatment with medicated feed, although feed quantity was restricted to that which could be consumed within a short period. The experiment was terminated after 112 feeding days, at which time all of the fish from each cage were weighed and counted. The culture performance of FRT was superior to that of O. mossambicus, indicating that FRT is more suitable for culture in marine cages (Table 5). FRT grew at a faster rate (2.56g/ day) and reached a larger size (439 g, 0.97 Ibs.) than O. mossambicus (2.08 g/day and 381 g, 0.84 Ibs.) Final cage biomass and survival were higher for FRT (16.6 kg, 36.6 Ibs. and 94.2%) than O. mossambicus (13.0 kg, 28.6 Ibs. and 83.3%). The feed conversion ratio was lower for FRT (2.52) than for O. mossambicus (3.56). The superior performance of FRT was probably due to its heritage from two saltwater-tolerant species (O. urolepis hornorum and O. mossambicus) and to a 10-year selective 17 Table 5. Mean + standard error of initial and final body weight, specific growth rate, weight gain, final cage biomass and survival rate of “Florida” red tilapia and O. mossambicus cultured in 2-m° cages for 112 days in seawater. “Florida” red O. mossambicus Initial body weight 152 +3 148+4 (g) Final body weight 439+2 381+ 21 (9) Specific growth rate 0.95 + 0.01 0.84 + 0.04 (%/day) Weight gain 2.56 + 0.01 2.08 + 0.17 (g/day) Final cage biomass 8.3+0.3 6.5: 2°1.5 (kg/m?) Survival rate 94.2 + 3.0 83.3 + 16.7 (%) breeding program for improved growth and color, whereas O. mossambicus originated from an unselected (wild) population. FRT grew at a slower rate in saltwater cages (2.56 g/day) than it did in freshwater cages (3.61 g/day), but this may have resulted from the different feeding regimes (once a day feeding in salt water compared to continuous feeding in fresh water). The bay was too rough for demand feeders. The underlying cause of the bacterial disease episode may have been poor nutrition. In an effort to obtain maximum growth rates, the fish were initially fed at a rate beyond satiation, contributing to the high feed conversion ratios. Large quantities of feed remained on the surface for several hours and became saturated with seawater, possibly leaching water-soluble nutrients. Ingestion of this water-soaked feed of reduced nutritional quality may have stressed the fish to the extent that their resistance to marine pathogens was weakened. Upon completion of the antibiotic treatment, the fish remained free of diseases at feeding rates that allowed them to consume the feed quickly. Based on these studies, in the Virgin Islands O. niloticus and “Florida” red tilapia are recommended for freshwater cage culture and “Florida” red tilapia is recommended for saltwater cage culture. Tilapia farmers should be aware that there are other species, strains and crosses that have not been tested here, and that tilapia breeding programs throughout the world are continually striving to improve growth characteristics. New breeds should periodically be tested under Virgin Islands conditions. Furthermore, individual farmers must establish their own breeding programs to prevent inbreeding and maintain the quality of their stocks. We wish to express our appreciation to Dr. Jonn Kubaryk, Department of Marine Sciences, University of Puerto Rico, for conducting the proximate analysis and to the Virgin Islands Food Fish Farm, Inc. for allowing us to use their facility. This research was supported in part by Hatch Project No. 80100. Agricultural Experiment Station Personnel Administration Darshan S. Padda.... Vice President for Research and Land Grant Affairs & Director James Rakocy....Associate Director Raquel Santiago Silver.... Assistant to the Vice President for Research and Land Grant Affairs Yvonne Horton....Administrative Assistant II Audrey Valmont Schuster....Administrative Assistant III Francis Diaz....Trades Leader Agronomy Martin Adjei....Research Assistant Professor, Agronomy Terry Gentry....Research Analyst I Osvaldo Lopez....Agricultural Aide III Antonio Rodriguez....Agricultural Aide II Animal Science Robert W. Godfrey....Research Assistant Professor, Animal Science Mark Gray....Research Specialist I Joni Rae Collins....Research Analyst Ill Victor Callas....Agricultural Aide IT Aquaculture James Rakocy....Research Professor, Aquaculture William Cole....Research Specialist II Donald Bailey....Research Specialist II Kurt Shultz....Research Analyst II Ezekiel Clarke.... Agricultural Aide IT Horticulture-Vegetables Manuel Palada....Research Assistant Professor Stafford Crossman....Research Specialist III Jacqueline Kowalski....Research Analyst I Paulino Perez....Research Assistant | Nelson Benitez.... Agricultural Aide II Reinardo Vasquez....Agricultural Aide II Horticulture-Ornamentals, Fruits, Forestry and Biotechnology Christopher Ramcharan....Research Assistant Professor Thomas Zimmerman....Research Specialist III James O’Donnell....Research Specialist I] Aberra Bulbulla....Research Analyst II Jeremiah Hassan....Agricultural Aide II Agustin Ruiz....Agricultural Aide Il 18 Current Research Projects Evaluation of Forage Conservation Systems in the Caribbean. Evaluation of Integrated Mechanical and Chemical Control of Casha (Acacia spp.) on Native Pasture. Improving Forage Feeding Value by Urea Treatment. Breeding and Biotechnology for Forage Yield, Quality and Persistence of Pennistems. Evaluation of Native Pasture and Agro-By-Product-Based Systems for Market Lamb Production. Herbage Allowance and Pasture Rotation Systems for Animal and Forage Production on Tropical Pasture. Increased Efficiency of Sheep Production. Reducing Effects of Heat Stress on Reproduction in Dairy Cattle. Evaluation of Tropical Adaptation of Non-Zebu Cattle Germplasm. Studies on the Production of Tilapia in Marine Cages. Evaluation of the Culture Potential of Selected Caribbean Marine Finfish. Integration of Tilapia and Hydroponic Vegetable Production in Recirculating Systems. Economic Analysis of Integrated Recirculating Systems. Integrating Tilapia Culture in Tanks with Field Production of Vegetable Crops. Micro-Irrigation of Horticultural Crops in Humid Regions. Evaluation of Saline Water for Irrigating Vegetable Crops in the U.S. Virgin Islands. Horticultural and Economic Evaluation of Vegetable Varieties in the U.S. Virgin Islands. Alley Cropping Systems for Sustainable Vegetable Production in the U.S. Virgin Islands. Improving Crop Management Systems for the Production of Culinary Herbs in the U.S. Virgin Islands. Evaluation of Horticultural Practices for Enhancing Root Crop Production in the Virgin Islands. Evaluation of Cultural Practices for Sweet Potato Weevil Control. Evaluation of Integrated Production Methods for Tropical Fruit Crops. - Evaluation of the Effects of Tissue Culture on Somatic Variation and Propagation of Breadfruit. Evaluation of Minor Tropical and Subtropical Fruits and Nuts for Production in the U.S. Virgin Islands. Evaluation of Trees for Agroforestry in the U.S. Virgin Islands. Potential for Ornamental Pot Crops in the Virgin Islands Using Growth Regulators. Transformation and Regeneration of Hibiscus and Bougainvillea. Effects of Bioherbicides on Competitive Ability of Nutsedge. Biochemical Basis of Resistance of Nutsedge Biotypes and Species to Nutsedge Rust. Recent Publications Adjei, M.B. 1992. Sorghum silage production from an alley cropping system. UVI Research. Agricultural Experiment Station, University of the Virgin Islands 4:14-16. Adjei, M.B., K. Albrecht and C.L. Wildeus. 1992. Performance of Desmanthus virgatus accessions in the Caribbean. Proceedings of the International Grasslands Congress, New Zealand and Queensland, Australia. (in press). Adjei, M.B., P. Mislevy and W. Chasen. 1992. Seed yield of bahiagrass in response to sward management by phenology. Agronomy Journal 84(2):599-603. Adjei, M.B. and W.D. Pitman. 1993. Response of Desmanthus to clipping on a phosphatic clay mine-spoil. Tropical Grasslands 27. (in press). Bailey, D.S. and J.E. Rakocy. 1992. Economics of tilapia culture in freshwater cages. UVI Research. Agricultural Experiment Station, University of the Virgin Islands 4:6-11. Cole, W.M., J.E. Rakocy, D.S. Bailey and J.A. Hargreaves. 1992. The effect of three pelleted diets on the survival, growth and feed conversion of juvenile white grunts (Haemulon plumeri). Proceedings of the Gulf and Caribbean Fisheries Institute-44, Merida, Mexico. (in press). 19 Collingwood, C.D., S.M.A. Crossman and M.C. Palada, 1992. Tomato germplasm evaluation for growth and productivity in the Virgin Islands. Proceedings of the Caribbean Food Crops Society-28, Santo Domingo, Dominican Republic. (in press). Courtney, C.H. and S. Wildeus. 1992. Epidemiology of parasitic gastroenteritis of sheep on St. Croix. Proceedings of the American Association of Veterinary Parasitologists 37:53. Crossman, S.M.A. 1992. Status of sweet potato weevil problems in the U.S. Virgin Islands. Proceedings of the International Conference on Sweet Potato Pest Management, Miami, Florida. (in press). Crossman, S.M.A. 1992. Sweet potato germplasm evaluation in the U.S. Virgin Islands. UVI Research. Agricultural Experiment Station, University of the Virgin Islands 4:4-5. Crossman, S.M.A. 1993. Sweet potato: a new look at an old crop. Virgin Islands Agriculture and Food Fair Bulletin No. 7: 33- 35. Crossman, S.M.A. and C. George. 1993. Sweet potato production in the Virgin Islands. Growers Factsheet No. 2, Cooperative Extension Service, University of the Virgin Islands. 4 pp. Crossman, S.M.A. and C. George. 1993. Vegetable varieties recommended for the Virgin Islands. Growers Factsheet No. 1, Cooperative Extension Service, University of the Virgin Islands. 8 pp. Crossman, S.M.A. and C.D. Collingwood. 1992. Herb production in the Virgin Islands. Celebrating Twenty Years of Learning and Growing. UVI Cooperative Extension Service, St. Thomas/St.John District Agriculture and Food Fair Bulletin, 10-11. Crossman, §.M.A., C.D. Collingwood and M.C. Palada. 1993. Effect of physical barriers on sweet potato weevil control. Proceedings of the Caribbean Food Crops Society-29, Fort de France, Martinique. (in press). Crossman, §.M.A., A.A. Navarro and C.D. Collingwood. 1992. The potential for year-round tomato production in the Virgin Islands. UVI Research. Agricultural Experiment Station, University of the Virgin Islands 4:11-13. Crossman, S.M.A., M.C. Palada and C.D. Collingwood. 1992. Yield evaluation of sweet potato cultivars in the U.S. Virgin Islands. Proceedings of the Caribbean Food Crops Society- 28, Santo Domingo, Dominican Republic. (in press). Hammond, A.C. and S. Wildeus. 1993. Effects of coconut meal or fish meal supplementation on performance and carcass characteristics in whole diet apparent digestibility of growing St. Croix lambs fed a tropical grass-based diet. Small Ruminant Research. (in press). Locasio, 8.J., G.A. Clark, A.A. Csinszky, C.D. Stanley, $.M. Olson, F. Rhoads, A.G. Smajstrala, G. Vellidis, R.D. Edling, H.Y. Hanna, M.G. Goyal, 8.M.A. Crossman and A.A. Navarro. 1992. Water and Nutrient Requirements for Drip- Irrigated Vegetables in Humid Regions. Southern Cooperative Series Bulletin 363. 17 pp. *Losordo, T.M., M.P. Masser and J.E. Rakocy. 1992, Recirculating aquaculture tank production systems: an overview of critical considerations. Southern Region Aquaculture Center Publication No. 451, Delta Branch Experiment Station, Stoneville, Mississippi. 8 pp. *Losordo, T.M., J.E. Rakocy and M.P. Masser. 1992. Recirculating aquaculture tank production systems: component options. Southern Region Aquaculture Center Publication No. 453, Delta Branch Experiment Station, Stoneville, Mississippi. 12 pp. *Masser, M.P., J.E. Rakocy and T.M. Losordo. 1992. Recirculating aquaculture tank production systems: management of recirculating systems. Southern Region Aquaculture Center Publication No. 452, Delta Branch Experiment Station, Stoneville, Mississippi. 12 pp. Mislevy, P., M.B. Adjei, G.M. Prine and F.G. Martin. 1992. Energycane response to harvest management. Soil and Crop Science Society of Florida Proceedings 51:79-84. O’Donnell, J.J. 1993. Mahogany (Swiefenia spp.) response to increasing water deficits. Proceedings of the Caribbean Food Crops Society-29, Fort de France, Martinique. (in press). O’Donnell, J.J. and M.B. Adjei. 1992. Symbiotic effectiveness of inoculated and indigenous rhibozia with six Leucana varieties. Agronomy Abstracts 264. O’Donnell, J.J. and M.C. Palada. 1993. Establishment and growth of four hedgerow species for alley cropping systems on St. Croix. Agronomy Abstracts 59. O’Donnell, J.J., J.P. Muir, G-E. Aiken, M.B. Adjei and W.D. Pitman. 1991, Response of ‘Florida’ Carpon Desmodium to inoculation with VA mycorrhizal fungi and rhizobia. Agronomy Abstracts: 273. O’Donnell, J.J., D.M. Silvia, W.D. Pitman and J.E. Rechcigl. 1992. Inoculation of Vigna parkeri with mycorrhizal fungi in an acid Florida spodosol. Tropical Grasslands 26:120-129. Palada, M.C., S.M.A. Crossman and C.D. Collingwood. 1992. Effect of organic and synthetic mulches on yield of basil under drip irrigation. Hortscience 27(6):99. (abstract). *Palada, M.C., B.T. Kang and S.L. Claassen. 1992. Effect of alley cropping with Leucana leucocephala and fertilizer application on yield of yegetable crops. Agroforestry Systems 19: 139-147. 20 Palada, M.C. 1993. Composting: an appropriate method of soil conservation for the U.S. Virgin Islands. Virgin Islands Agriculture and Food Fair Bulletin No. 7:36-39. Palada, M.C., 8.M.A. Crossman and C.D. Collingwood. 1993. Irrigation water use and yield of thyme in the Virgin Islands. Proceedings of the Caribbean Food Crops Society-29, Fort de France, Martinique. (in press). Palada, M.C., S.M.A. Crossman and C.D. Collingwood. 1993. Yield Performance of Vegetable Varieties in the U.S. Virgin Islands: 1988-1992. Technical Bulletin No. 5. Agricultural Experiment Station, University of the Virgin Islands. 28 pp. Palada, M.C., S.M.A. Crossman, C.D. Collingwood and J.A. Kowalski. 1993. Water use and yield of bell peppers in hedgerow intercropping with drip irrigation. Agronomy Abstracts. (in press). Phelps, R.P., W. Cole and T. Katz. 1992. Effect of fluoxymesterone on sex ratio and growth of Nile tilapia, Oreochromis niloticus (L.). Aquaculture and Fisheries Management 23:405-410. *Rakocy, J.E. 1992. Feasibility of using vegetable hydroponics to treat aquaculture effluents. Pages 347-350 in J. Blake, J. Donald and W. Magette, editors. Proceedings of the National Livestock, Poultry and Aquaculture Waste Management Workshop. Kansas City, Missouri. Rakocy, J.E. 1992. Waste management in integrated recirculating systems. Twenty-first Symposium of the United States-Japan Natural Resources Panel, 1992, Kyoto, Japan. (in press). *Rakocy, J.E., T.A. Losordo and M.P. Masser. 1992. Recirculating aquaculture production systems: integrating fish and plant culture. Southern Regional Aquaculture Center Publication No. 454, Delta Branch Experiment Station, Stoneville, Mississippi. 8 pp. Rakocy, J.E. and J.A. Hargreaves. 1993. Integration of vegetable hydroponics with fish culture: a review. Pages 112-136 in J.- K. Wang, editor. Proceedings of the Aquaculture Engineering Conference on Techniques for Modern Aquaculture. Aquacultural Engineering Group, American Society of Agricultural Engineers. Rakocy, J.E., J.A. Hargreaves and D.S. Bailey. 1993. Nutrient accumulation in a recirculating aquaculture system integrated with hydroponic vegetable production. Pages 148-158 in J.- K. Wang, editor. Proceedings of the Aquaculture Engineering Conference on Techniques for Modern Aquaculture. Aquacultural Engineering Group, American Society of Agricultural Engineers. Ramcharan, C. 1992. A low cost chemigator for the irrigation of fruit crops. Proceedings of the Caribbean Food Crops Society- 28, Santo Domingo, Dominican Republic. (in press). Ramcharan, C. 1992. The potential of Christmas Snowflake as a Christmas pot crop using growth retardants. UVI Research. Agricultural Experiment Station, University of the Virgin Islands 4:17-18, 20. 21 Wildeus, S. 1993. Age-related changes in scrotal circumference, testis size and sperm reserves in bulls of the tropically-adapted Senepol breed. Animal Reproduction Science. (in press). Wildeus, S. and C.H. Courtney. 1992. Influence of gastrointestinal parasite control on body weight, blood parameters and fecal egg counts in hair sheep ewes and lambs in the dry tropics. Journal of Animal Science 70:585. (abstract). Wildeus, S. and A.C. Hammond. 1993. Testicular, semen, and blood parameters in adapted and nonadapted Bos taurus bulls in the semi-arid tropics. Theriogenology 40:345-355. Wildeus, S. and A.C. Hammond. 1993. Effects of supplementation on body weight change and postpartum interval in lactating hair sheep ewes grazing tropical pastures. Journal of Animal Science 71(Supp. 1):25. (abstract). Wildeus, S. and G. Willock, Jr. 1993. Physiological response of three sheep breeds to summer temperatures on St. Croix. Virgin Islands Agriculture and Food Fair Bulletin No. 7:51-53. Wildeus, S., J.R. Collins and M.L. Gray. 1993. Lambing performance and postpartum interval in hair and wool sheep ewes under tropical conditions. Journal of Animal Science 71(Supp. 1):242. (abstract). Wildeus, S., M.L. Gray and J.R. Collins. 1993. Seasonal effects on pubertal characteristics in hair and wool sheep ewe lambs under tropical conditions. Journal of Animal Science 71(Supp. 1):119. (abstract). *Wildeus, S., L.R. McDowell and J.R. Fugle. 1992. Season and location effects on serum and liver mineral concentrations of Senepol cattle on St. Croix. Tropical Animal Health & Production 24:223-230. Wright, D.W., H.D. Hupp, R.J. Deans and I.L. Mao. 1992. Growth characteristics of Senepol bulls fed various energy levels over different time periods, under tropical conditions. Tropical Agriculture (Trinidad) 69(2):181-185. Wright, D.W., S. Wildeus, C.J. Brown and Z.B. Johnson. 1992. Expected progeny differences for weaning weight in the Senepol breed. UVI Research. Agricultural Experiment Station, University of the Virgin Islands 4:2-4. Zimmerman, T.W. 1993. Dwarfing plants through applied biology. 1993. Proceedings of the Caribbean Food Crops Society-29, Fort de France, Martinique. (in press). *An asterisk in front of an entry indicates that it has been previously listed, but was in press before. Now the entry is complete.