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A.K. Carter and C.S. Vavrina

Chile (Capsicum annuum L.) seeds sown in July for fall transplants in the greenhouse often yield poor stands due to thermoinhibition. To determine cultivar response to high temperature, five jalapeno cultivars and one cayenne cultivar used commercially in Florida and New Mexico were tested. Two seedlots of `Cayenne, Large Red Thick', `Ole', `Jalapeno M', `Mitla', and `Tam Veracruz', and one seedlot of `Ebano' were evaluated on a thermogradient table at a temperature range of 20, 25, 30, 35, and 40°C. Percent germination, mean daily germination, and germination performance index were calculated. Additional seeds were soaked for 24 hours at 25, 30, 35, and 40°C. The exudate was then measured for electrical conductivity and glucose equivalents as an indication of seed leakage. All cultivars exhibited thermoinhibition, but the critical temperature of onset varied among cultivars. `Ebano' had the highest germination performance index across all temperatures among the six cultivars. At 40°C, however, no cultivar exceeded 4.0% germination. There was significant variation in germination performance between seedlots of some cultivars. The electrical conductivity and the number of glucose equivalents leached from the seed varied among cultivars, but did not correlate with decreased germination. Thermoinhibition in chile is probably due to factors other than those associated with membrane leakage.

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C.S. Vavrina and F.M. Roka

In 4 years of research comparing production of short-day onions (Allium cepa L.) on plastic mulch versus bare ground in southern Florida, greater marketable yields were obtained when onions were grown on plastic mulch. Results showed that in a semitropical environment, white-on-black plastic mulch provided the greatest yield enhancement from increased weight and bulb size. Yield loss due to splitting, while apparent, was not sufficient to reduce the impact of mulch on the increase in individual bulb weight. Adopting plastic mulch for sweet onion production will add between $400 and $500/acre ($988 and $1,235/ha) of additional operating expenses. While this may increase cash-flow burdens and heighten overall financial risks, the added value from increased yields by weight and greater percentages of jumbo sized bulbs suggest that plastic mulch has an excellent chance to increase a grower's overall net return. Using conservative yield and market price assumptions, an economic analysis showed an increase in grower's net return of more than $120/acre ($296/ha).

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E.T. Maynard, C.S. Vavrina, and W.D. Scott

Muskmelon (Cucumis melo L. cvs. Superstar and Mission) transplants were grown in seedling flats with individual cells ranging in volume from 7 to 100 cm3. The smallest cells were in a 338-cell polystyrene flat 33 cm wide × 66 cm long × 4.75 cm deep; the largest cells were in a 32-cell plastic flat 30.5 × 50.8 × 6.5 cm. The study was conducted in Florida and Indiana during the 1993 and 1994 growing seasons. Seedlings of uniform age were transplanted to the field and grown to maturity using standard cultural practices. Early yield of `Superstar' muskmelon, measured as number of fruit per plot or percentage of total yield, increased as transplant cell volume increased. In one trial, plants from 7-cm3 cells produced no early yield, while plants from 100-cm3 cells produced 40% of the total yield in the first three harvests. In three of the four trials, total yield of `Superstar' increased as cell volume increased. Marketable early yield of `Mission' muskmelon, measured as number or weight per plot, increased as cell volume increased in three of four trials. In Florida, total yield of `Mission' also increased as cell volume increased. Size of `Superstar' fruit was not influenced by cell volume. In Florida, size of early `Mission' fruit increased as cell volume increased.

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Francis X. Mangan, Charles S. Vavrina, and John C. Howell

The effects of transplant depth on lodging and yield were evaluated in five experiments in Florida and Massachusetts. `Cherry Bomb', `Jupiter', and `Mitla' pepper (Capsicum annuum L.) transplants were set at three depths so that the soil surface was even with the top of the rootball, the cotyledon leaf, or the first true leaf. Seedlings set to the depth of cotyledon leaves or to the first true leaf lodged less than did those set to the top of the rootball. No yield differences were recorded among treatments in Massachusetts; however, total weight of red fruit was greater in treatments that lodged less in 1 of the 2 years, suggesting that lodging delayed maturity. Soil temperature in Massachusetts declined at the level of the rootball as planting depth increased.

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C.S. Vavrina, P.A. Stansly, and T.X. Liu

Household detergents were evaluated in field studies on fresh-market tomato (Lycopersicon esculentum Mill.) for insecticidal and phytotoxic effects. Laboratory bioassays were used to examine the toxicity of a household liquid dish detergent on small nymphs of silverleaf whitefly, Bemisia argentifolii Bellows and Perring. The detergents tested proved to be more toxic to whitefly nymphs than the commercial insecticidal soap. Detergent treatments were applied to tomato with a commercial high pressure hydraulic sprayer at 0%, 1%, 2%, 4%, and 8% (by volume) initially and at 0%, 0.25%, 0.5%, 1.0%, and 2.0% (by volume) in subsequent tests. As detergent rate, frequency of application, or both increased, plant dry weight accumulation and fruit yield decreased. Applying detergent also increased time to fruit maturity. A once-a-week application of 0.25% to 0.5% detergent initially applied 2 weeks after transplanting alleviated phytotoxicity and yield reduction problems.

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C.S. Vavrina, G.J. Hochmuth, J.A. Cornell, and S.M. Olson

Fall-grown tomato (Lycopersicon esculentum Mill.) transplants were larger than spring-grown transplants when fertilized in the greenhouse with NH3NO3 at 0, 15, 30, 45, 60, or 75 mg·L-1 N in a standard 1/4 strength Hoagland's solution. All transplant growth characteristics measured (stem length, leaf area and number, root and shoot dry mass) increased linearly with increasing N in both seasons. However, in the fall, when greenhouse temperatures and light levels were higher, stem length, leaf area, root: shoot ratio, and the ratio of shoot dry weight: leaf area responded quadratically. In the spring, total fruit yield and production of extra-large fruit increased with increasing transplant N fertilization, but the opposite trend occurred in the fall. These differing seasonal responses suggest fundamental differences in tomato transplant growth that must be addressed by modifications in N fertilization between spring and fall.

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Nancy Kokalis-Burelle, C.S. Vavrina, M.S. Reddy, and J.W. Kloepper

Greenhouse and field trials were performed on muskmelon (Cucumis melo) and watermelon (Citrullus lanatus) to evaluate the effects of six formulations of plant growth-promoting rhizobacteria (PGPR) that have previously been shown to increase seedling growth and induce disease resistance on other transplanted vegetables. Formulations of Gram-positive bacterial strains were added to a soilless, peat-based transplant medium before seeding. Several PGPR treatments significantly increased shoot weight, shoot length, and stem diameter of muskmelon and watermelon seedlings and transplants. Root weight of muskmelon seedlings was also increased by PGPR treatment. On watermelon, four PGPR treatments reduced angular leaf spot lesions caused by Pseudomonas syringae pv. lachrymans, and gummy stem blight, caused by Didymella bryoniae, compared to the nontreated and formulation carrier controls. One PGPR treatment reduced angular leaf spot lesions on muskmelon compared to the nontreated and carrier controls. On muskmelon in the field, one PGPR treatment reduced root-knot nematode (Meloidogyne incognita) disease severity compared to all control treatments.

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E.W. Stover, P.J. Stoffella, S.A. Garrison, D.I. Leskovar, D.C. Sanders, and C.S. Vavrina

A commercial mixture of 1-naphthaleneacetamide and 1-naphthaleneacetic acid (Amcotone) was applied to tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.) at various timings from early bloom through early fruit development to evaluate effects on fruit size and both early and total marketable yield. Amcotone was applied at rates from 10 to 40 mg·L-1, at three sites for each of the species studied. Measured yield response variables in tomato did not differ between the control and Amcotone treatments, regardless of location. Amcotone treatments did not affect yields or fruit size for pepper at the New Jersey or Texas sites. However, at Ft. Pierce, Fla., early marketable yield of pepper was increased in plots receiving three Amcotone applications at 10 mg·L-1, but total marketable yield was significantly reduced in all plots receiving more than two Amcotone sprays, and mean fruit weight was reduced by all Amcotone treatments. Early and total marketable yield of pepper at Ft. Pierce were markedly reduced in plots receiving four applications of 40 mg·L-1, which was a high rate used to assess potential phytotoxicity. While minimal benefit from auxin application was observed in this study, earlier studies suggest that these results may have been influenced by favorable environmental conditions for fruit development or negative effects on unopened flowers during all Amcotone spray applications.

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M. Arenas, C.S. Vavrina, J.A. Cornell, E.A. Hanlon, and G.J. Hochmuth

Sixteen media prepared from peat, coir, vermiculite, or perlite were used to determine the optimum growing media for tomato (Lycopersicum esculentum Mill.) transplants. Medium composition did not affect tomato seed emergence, although seedling emergence was higher in winter (90%) than summer (85%). Greatest transplant root dry weight, stem diameter, and leaf area were achieved in 50% to 75% peat + 25% to 50% vermiculite in summer. In winter, greatest transplant root dry weight, stem diameter, and leaf area were achieved in eight media: 100% peat, 75% peat + 25% vermiculite, 75% peat + 25% perlite, 50% peat + 50% vermiculite, 50% peat + 50% perlite, 25% peat + 50% coir + 25% vermiculite, 50% peat + 25%coir + 25% vermiculite, and 25% peat +25% coir +25% vermiculite +25% perlite. Transplants grown with >50% coir exhibited reduced plant growth compared to peat-grown transplants, a response that may be associated with high N immobilization by microorganisms and high C:N ratio. Despite transplant growth differences during the summer, fruit yields generally were unaffected by transplant media.