In recent decades, F 1 hybrids in the genus Cucurbita have increasingly gained prominence over open-pollinated varieties, particularly in summer squash, ornamental pumpkin and acorn cultivars of C. pepo L. and kabocha cultivars of C. maxima
Chien Yi Wang
The endogenous levels of abscisic acid (ABA) in zucchini squash were increased by temperature conditioning at 10°C for 2 days. This temperature conditioning treatment reduced the severity of chilling injury in the squash during subsequent storage at 2.5°C. The ABA levels remained higher in treated squash than in untreated samples throughout storage. Direct treatments of squash with ABA at 0.5 mM and 1 mM before storage at 2.5°C increased ABA levels in the tissue and were also effective in reducing chilling injury. The involvement of ABA in reducing chilling injury will be discussed.
G.H. Clough, S.J. Locascio, and S.M. Olson
Broccoli (Brassica oleracea L. var. italica), followed by tomato (Lycopersicon esculentum Mill) or squash (Cucurbita pepo L. var. melopepo), and then broccoli were produced in succession re-using the same polyethylene-mulched beds at two locations with different soil types. First-crop broccoli yield was earlier and greater with drip than with overhead irrigation and increased as N-K rate increased from 135-202 to 270-404 kg·ha-1. On a tine sandy soil, yields of second and third crops produced with residual or concurrent fertilization increased with an increase in N-K rate. On a loamy fine sandy soil, yields also increased as the rate of residual N-K increased; yields of second and third crops did not respond to rate of concurrently applied N-K, but were higher with concurrent than with residual fertilization, except total tomato yields were similar with either application time. With drip irrigation and concurrent weekly fertigation, yields equalled or exceeded those obtained with preplant fertilization and overhead irrigation.
Chien Yi Wang
Temperature conditioning of zucchini squash (Cucurbita pepo L.) at 15°C for 2 days enhanced polyamine levels and delayed the development of chilling injury during storage at 5°C. Direct treatment of zucchini squash with polyamines increased the endogenous levels of polyamines and reduced chilling injury. However, treatment with polyamine inhibitors after harvest but before temperature conditioning suppressed the increase of endogenous polyamines and reduced the benefit obtained from temperature conditioning. These results suggest that the resistance of squash to chilling injury may be related to the endogenous levels of polyamines.
J. Pablo Morales-Payan* and William M. Stall
A field experiment was conducted in Live Oak, Fla., to determine the effect of yellow nutsedge (Cyperus esculentus L.) (YN) density and time of emergence on the yield of direct-seeded squash (Cucurbita pepo L.). YN densities (0, 20, 40, 60, and 100 plants/m2) were established from tubers planted at different times onto polyethylene-mulched beds, so that YN would emerge the same day as the crop or 5, 15, or 25 days later than the crop (DLTC). YN was not controlled after its emergence. The extent of squash yield loss was affected by YN density and time of emergence. When YN emerged the same day as the crop, the yield of squash was reduced by ≈7% (20 YN/m2) to 20% (100 YN/m2). When YN emerged 15 DLTC, crop yield loss was ≈13% at the density of 100 YN/m2>. Regardless of density, YN emerging 25 DLTC did not significantly reduce crop yield as compared to weed-free squash. Thus, in soils with high YN densities (≈100 viable tubers/m2) herbicides and/or other means of YN suppression in squash should be effective for at least 25 days after crop emergence to prevent significant yield loss. If squash yield losses <5% were acceptable, YN control may not be necessary when densities <20 YN/m2 emerge at any time during the squash season or when <100 YN/m2 emerge >25 DLTC. However, YN emerging during the first 15 days of the squash season may produce tubers, which could increase the YN population at the beginning of the following crop season.
J.E. Brown, R.P. Yates, W.T. Hogue, C. Stevens, and V.A. Khan
Yellow crookneck `Dixie' hybrid summer squash, Cucurbita pepo L. var. melopeop Alef., was evaluated at E.V. Smith Research Center, Shorter, Alabama. Summer squash was grown in single rows spaced 6 feet apart. Plants were seeded 18 inches apart within 20-foot row plots. Treatments were: 1) black plastic mulch (BPM), 2) yellow painted plastic mulch (YPM), 3) white plastic mulch (WPM), 4) bare soil (BS), 5) aluminum painted plastic mulch (APM) and 6) bare soil with Diazinon insecticide (BSI). Aphid traps caught more aphids in BS or BPM plots than those from APM or YPM plots. The onset of mosaic disease incidence of squash infected with the two viruses identified as zucchini yellow mosaic and cucumber mosaic was delayed by as much as three weeks when compared to BSI or BS. Summer squash planted in APM, WPM, YPM and BPM produced 96%, 98%, 75% and 21%, respectively, more total squash yield than that produced on bare soil (control). A higher percentage of green squash (virus infected) was produced from plants grown over BPM (72%), BSI (68%), BS (59%), YPM (57%) or WPM (57%) than from APM (39%)
Jim E. Wyatt
Many summer squash hybrids initiate flowering by first producing one or more pistillate flowers before the development of any staminate flowers. These first pistillate flowers have no pollen source unless an earlier squash planting is nearby. The objectives of this study were to measure the loss in yield incurred by the absence of pollination and to determine if sex expression in squash could be altered by use of gibberellic acid (GA). `Cougar' summer squash was planted in 12 isolated plots on 13 May; four plots had adjacent rows planted on 3 May to provide pollen for the earliest developing pistillate flowers in those plots. On 28 May, 0.146 L·ha-1 of GA (ProGibb 4®) was applied to an adjacent row in four of the plots planted on 13 May. The four control plots received no treatment. At anthesis, pistillate and staminate flowers were counted daily for 10 days. The first six pistillate flowers that bloomed in each plot were identified and measured (length and diameter) on the day of anthesis, and at 4 and 7 days after anthesis. Fruit were harvested five times at 2-day intervals and data are reported on fruit ≤5.7 cm in diameter. GA had no effect on squash flowering habit. At 4 and 7 days after anthesis, fruit were smaller in plots where no pollen source was available. Early yields were higher for the first two harvests in plots where pollinators were present. A small, early planting of squash should be made to provide staminate flowers for normal growth and development of early fruit on the main summer squash crop.
Laura C. Merrick, Frank Drummond, Constance Stubbs, and Rhonda Weber
Managed and feral honey bee (Apis mellifera) colonies have declined dramatically in the past decade due largely to parasitic mites, pesticide contamination, and severe weather. Squash (Cucurbita spp.) is one of many agricultural crops whose production may be negatively effected by decline of these pollinators. A study was conducted on a set of nine farms in Maine to assess the relationship between bee abundance and fruit set of summer and winter squash. The organic and conventional farms targeted in the study included farms with and without the presence of honey bees. With winter squash, fields with more bees tended to exhibit higher fruit set. The average fruit set was slightly higher for farms with honey bees (42%) vs. those without (35%), but both types of farms were similar to that found in controlled hand pollinations (31% on average). In contrast, fruit set for summer squash averaged 95% to 96% for all farms, regardless of the relative abundance of censused bees. Bumble bees (Bombus spp.) were the most abundant wild bees found pollinating squash. Farms with honey bees on average had higher numbers of bees in squash flowers than farms without honey bees, although a difference in preference for floral sex type was detected for bee taxa. Honey bees were much more likely to be found in female flowers, while bumble bees were more abundant in male flowers. Significantly more native bees were found in squash flowers on farms without honey bee hives, although native bees were still present to some extent on farms that were dominated by Apis mellifera.
Fabio Mencarelli, Werner J. Lipton, and Sharon J. Peterson
Zucchini squash (Cucurbita pepo L.) was stored 2 weeks at 2.5°, 5°, or 10°C and with 1%, 2%, 4%, 8%, or 21% O2 and then was aerated 2 days at 10°. Low O2 levels inhibited the rates of CO2 and ethylene production, particularly at 5° and 10°. Both rates increased during aeration, but much more in samples held previously at 2.5° or 5° than in those from 10°. About 75% and 55%, respectively, of the burst in CO2 production in samples from 2.5° and 5° was due to exposure to low temperature; the remainder was attributed to the effect of exposure to low O2 levels. For ethylene production, the corresponding values were about 95% and 70%. Zucchini squash stored at 5° for 2 weeks was virtually free of chilling injury (Cl), surface mold, decay, or off-flavors; almost all of the fruit still was rated good to excellent in appearance. About ¾ of the squash was still in this category after 2 additional days at 10°. At 5°, squash did not benefit from storage in low-O2 atmospheres. Storage at 2.5° induced severe Cl, which was ameliorated by holding the squash in 4%, 2%, or 1% O2 instead of in 21% or 8% O2. However, amelioration was no longer evident after 2 days of aeration at 10°. Defects not related to Cl—especially off-flavors—developed most noticeably in squash held at 10°; the benefit from low O2 levels was slight. Storing zucchini squash at 6° ± 2° likely would be optimal if it must be held longer than a few days.
M. Ozores-Hampton, H.H. Bryan, B. Schaffer, and E.A. Hanlon
The effects of municipal solid waste (MSW) materials on growth, yield, and mineral element concentrations in tomato (Lycopersicon esculentum Mill.) (1991 and 1992) and squash (Cucurbita maxima Duch. Ex Lam.) (1992 and 1993) were evaluated. Agrisoil compost (composted trash), Eweson compost (co-composted trash and sewage sludge), or Daorganite sludge (chemically and heat-treated sewage sludge) were incorporated into calcareous limestone soil of southern Florida. The control had no MSW material added to the soil. The effect of MSW on crop growth, yield, and mineral element concentrations varied considerably between years for tomato and squash. In 1991, tomato plants grown in soil amended with Eweson or Daorganite had a greater canopy volume than plants in the control treatment. Tomato plants grown in Daorganite had greater total fruit weight (1991) than plants in Agrisoil and more marketable fruit (1992) than control plants. In both years, tomato plants in Agrisoil had higher root Zn concentrations than plants in the other treatments. In 1992, tomato plants in Eweson had lower root Mn concentrations than plants in the other treatments, whereas Mg concentrations in the roots were higher in the Daorganite treatment than in Eweson. Tomato plants in Agrisoil had higher Pb concentrations in the roots than plants in all other treatments. In 1991, leaves of tomato plants in Agrisoil had lower Ca concentrations than leaves of plants in the control treatment. In 1992, leaf Zn concentrations were greater for tomato and squash in Agrisoil than in the control or Daorganite. In 1992, canopy volume and yield of squash were greater for plants in Daorganite than for plants in the control and other MSW treatments. Although canopy volume and total squash fruit weight did not differ among treatments in 1993, plant height was greater for squash plants in the MSW treatments than for those in the control. In 1993, leaf Mg concentrations were greater for squash grown in Daorganite than for plants in the control or Agrisoil. In 1993, fruit Cd concentration was higher for plants with Eweson than for plants in the control or Agrisoil. However, the fruit Cd concentration in squash grown in Eweson compost (1.0 mg/kg dry weight) was far below a hazardous level for human consumption. Our results indicate that amending calcareous soils with MSW materials can increase growth and yield of tomato and squash with negligible increases in heavy metal concentrations in fruit.