Control of downy (Pseudoperonospora cubensis) and powdery mildew [(Podosphoera xanthii (Sphaerotheca fuliginea)] on `Sweet Dumpling' winter squash (Cucurbita maxima) was evaluated at the University of Florida, IFAS, Indian River Research and Education Center (IRREC) in Fort Pierce, Florida during Spring 2004. Seven foliar spray fungicide treatments were evaluated against an untreated control. Powdery and downy mildew ratings (estimated percentage of foliage damage) and marketable yields (mt/ha) were measured. Plants in the untreated plots had significantly higher powdery and downy mildew ratings. All fungicide treatments reduced powdery mildew on adaxial leaf surfaces. Downy mildew appeared unusually late in the crop season and all fungicide treatments significantly reduced it. There were no significant differences among treatments for marketable yield. Although the level of disease occurrence was not sufficient to reduce yields, each foliar spray treatment significantly reduced powdery and downy mildew.
A.H. Beany, K. Pernezny, P. J. Stoffella, N. Havranek, and J. Sanchez
Jim E. Wyatt, James A. Mullins, and Charles A. Mullins
Several spacing, cultivar, ethephon and harvest sequence studies were made on summer squash in 1989 evaluating cultural practices which maximized marketable once-over yield of fruit for processing. Optimum spacing was 30 cm within rows and 45 cm between rows. The zucchini and yellow hybrids producing the highest marketable yield were `Classic' and 'Gold Slice', respectively. Ethephon applied at 0.77 kg/ha resulted in higher yield than no ethephon. Harvesting two times followed by a seven day delay before a once-over, destructive harvest produced a marketable yield equal to three harvests/week for three weeks. A prototype mechanical harvester has been used successfully on yellow hybrids; zucchini hybrids require more force for successful fruit separation.
Paula P. Chee
Plant regeneration from tissue cultures of summer squash (Cucurbita pepo L. ev. YC60) has been observed. Embryogenic callus tissues were initiated when cotyledons of mature seeds were excised and cultured on Murashige and Skoog (MS) medium supplemented with either 22.7 μm 2,4-D or a combination of 4.7 μm 2,4,5-T, 4 μm BA, and 0.5 μm kinetin. Clusters of somatic embryos were found in callus tissue. Maturation of these somatic embryos was effected by transfer of embryogenic callus tissues to MS supplemented with 0.5 μm NAA and 0.25 μm kinetin. Regenerated mature plants were morphologically normal and set fruits containing seeds that germinated normally. Chemical names used: 6-benzylaminopurine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); α - napthaleneacetic acid (NAA); 2,4,5-trichlorophenoxyacetic acid (2,4,5-T).
A.H. Beany, K. Pernezny, P. J. Stoffella, N. Havranek, and J. Sanchez
Control of downy (Pseudoperonospora cubensis) and powdery [(Podosphoera xanthii (Sphaerotheca fuliginea)] mildew on `Sweet Dumpling' winter squash (Cucurbita maxima) was evaluated at the University of Florida, IFAS, Indian River Research and Education Center (IRREC), in Fort Pierce, Florida during the Spring of 2005. Three foliar spray fungicide treatments were evaluated against an untreated control. Powdery and downy mildew ratings (estimated percentage of foliage damage) and marketable yields (mt/ha) were measured. Plants in the untreated plots had significantly higher powdery and downy mildew ratings. All fungicide treatments significantly reduced both mildews. There were no significant differences among treatments for marketable yield. Although the level of disease occurrence was not sufficient to reduce yields, Gavel alternated with Nova, Bravo Ultrex weekly, and Cabrio + Forum alternated with Bravo Ultrex + Manzate 75WG reduced downy mildew by ≥50%.
Willie O. Chance III and Harry A. Mills
Mature zucchini squash plants (Cucurbita pepo L.) were grown under four NO3:NH4 ratios (1:0, 3:1, 1:1, and 1:3) to determine effects on macronutrient nutrition. Plants were grown in solution culture under greenhouse conditions. Treatments were applied at first bloom. Highest uptake of Ca and Mg occurred in the 1:0 NO3:NH4 treatment while higher K uptake was found in the 3:1 NO3:NH4 treatment. Total nitrogen uptake was greatest in the 1:1 and 3:1 NO3:NH4 treatments. A 3:1 NO3:NH4 ratio applied at first bloom gave best overall uptake of N, K, Ca, and Mg.
D. Scott NeSmith
Summer squash (Cucurbita pepo L.) was grown under greenhouse conditions in 0.35, 2.00, or 7.60 liter containers with full light or with 50% full light to determine the effects of root restriction and reduced light on crop growth and development. Leaf area was determined nondestructively over the course of the experiment, and destructive plant samples were taken weekly to determine dry matter accumulation and partitioning. The experiment was repeated to validate results. There was a decline in production of plant leaf area and dry matter accumulation in response to increased root restriction under full light conditions. However, under 50% light, root restriction had less impact on plant growth when comparing the 2.00 and 7.60 liter container plants. Under the most severe root restricting conditions, light level had little impact on leaf area production and dry matter accumulation. There were no consistent differences in leaf chlorophyll attributable to root restriction or reduced light; however, there was a trend for decreased leaf weight per unit of leaf area under low light conditions. Fruit dry matter production was notably diminished under severe root restriction in full light, and under all root environments under 50% light.
Kent Cushman, Jin Huan, and Lisa Cushman
Grafting of watermelon scions onto squash or pumpkin (Cucurbita), bottle gourd (Lagenaria), wax gourd (Benincasa), or watermelon (Citrullus) rootstocks is practiced in most of the major watermelon production regions of the world. Advantages of grafting are protection against soilborne diseases, resistance to nematodes, and overall increased vigor of plants resulting in higher yield and better fruit quality. Disadvantages include increased cost of seedling production and the potential of altered horticultural characteristics of cultivars used as scions. With problems associated with watermelon vine decline in recent years in Florida and the increasing cost of soil fumigants, the use of grafted watermelon seedlings should be explored. Four grafting techniques for watermelon are common: splice, side insertion, approach, and hole insertion. The approach graft, though labor intensive, doesn't require exacting control of temperature and humidity after making grafts and may be well suited to south Florida conditions. All other grafts require excellent control of the post-grafting environment and a careful transition from low light and high humidity to high light and low humidity. A preliminary evaluation of grafted and ungrafted plants during Fall 2005 compared `Tri-X 313', `Palomar', `Precious Petite', and `Petite Perfection' on several rootstocks. Most rootstock/scion combinations produced fruit of normal size, appearance (internal and external), and soluble solids content. Some combinations resulted in irregular, pumpkin-shaped fruit and slightly higher incidences of hollowheart.
Vuvu D. Manseka and James R. Hicks
Butternut squash was harvested at two stages of maturity in 1994 and was cured for 10 days at 26°C and 80% or 95% relative humidity (RH) before storage in air at 12°C and 65% or 80% RH for 144 days. Fresh weight was assessed right after harvest along with carotene (milligram per 100 grams fresh weight), carbohydrates (milligrams per gram dry weight) and internal color (L, a, b). Percent weight loss and all quality components were assessed immediately after curing and every 48 days thereafter. Weight loss increased with days in storage and was substantially minimized by a humidified environment down to 6%. The 95% curing treatment reduced weight loss to levels below the upper threshold for consumer acceptance (<15%) after 144 days. Maturity at harvest did not affect weight loss during storage, but rather the percent dry weight. Beta-carotene increased by >100% during storage. A positive correlation was established between weight loss and beta-carotene and also between the a value and beta-carotene. Curing at 95% RH obviously reduced beta-carotene content to less than one-third of its corresponding amount in noncured fruit. Sucrose increased as glucose and fructose and starch decreased during storage in cured and noncured fruit. Starch was found to decrease by 26% after 144 days in storage. The lowest levels of starch were found early during storage in fruit cured at 95% RH, but the difference between treatments disappeared by the end of storage.
Jorge Pérez-Arocho and Linda Wessel-Beaver
Melonworm (Diaphania hyalinata) is one of the most damaging pests of squash and pumpkin (Cucurbita sp.) in tropical/subtropical regions of the Americas. In order to identify sources of resistence to melonworm, we evaluated 345 accessions of C. moschata, including both tropical and temperate types, originating from the Americas, Europe, Asia, and Africa. C. argyrosperma (65 accessions) was also evaluated. Accessions were field tested in five single-plant complete blocks planted over a 9-month period in Isabela, P.R. Each plant was evaluated for foliar damage (0–4 scale) at 3 and 6 weeks. Larval counts were made on a five-leaf sample at 8 weeks. Accessions were classified for degree of leaf mottling and pubescence. Differences among accessions were found for foliar damage and number of larva, but ranking of accessions varied, depending on the criteria used to measure resistance. In order to establish independent culling levels, we considered the lower 30% of accessions for each trait. The upper limit was ≤0.42 for foliar damage at 3 weeks, ≤0.50 damage at 6 weeks, and ≤1.25larva/plant. This led to the selection of 34 resistant accessions. We used a similar technique to identify the most susceptible accessions. The susceptible accessions will be used as a control group when the 34 selections are further evaluated. Within C. moschata, accessions with either green leaves or less pubescence had less leaf damage and fewer larva than accessions with mottled leaves or more pubescence. As a group, C. argryosperma accessions were more susceptible, and nearly all had mottled leaves and little pubescence. Untested accessions with green leaves and/or little pubescence might yield additional sources of resistance to melonworm.
Michael P. Hoffmann, Richard W. Robinson, Margaret M. Kyle, and Jonathan J. Kirkwyland
Seventy-six Cucurbita pepo L. cultivars and breeding lines were evaluated under field conditions for infestation levels and defoliation (leaf area consumed by beetles) by adult diabroticite beetles in 1992 and 1994. Striped and spotted cucumber beetles, Acalymma vittatum (F.) and Diabrotica undecimpunctata howardi Barber, respectively, were most common, but some western and northern corn rootworms, D. virgifera virgifera LeConte and D. barberi Smith and Lawrence, respectively, also were present. In general, pumpkin, delicata, acorn winter squash, scallop, and yellow straightneck summer squash types were the least infested and defoliated. Caserta/yellow, zucchini, caserta/zucchini, caserta, and precocious yellow straightneck types were the most infested and defoliated. The number of beetles per plant was correlated (r ≥ 0.72) with leaf defoliation and proportion of plants infested, indicating that beetle infestation is a good predictor of damage. The cultivars and breeding lines that were the least infested and defoliated can be used in breeding programs to develop desirable genotypes with reduced beetle preference. Conversely, those genotypes that were highly preferred have potential as trap crops for these beetle pests.