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John S. Caldwell and Paul Clarke

Cucumber (Cucumis sativus L.) and squash (Cucurbita pepo L.) were grown in a replicated trial on three types of plastic mulch: solid black plastic mulch, solid aluminum-coated plastic mulch with a silver reflective appearance, and black plastic mulch with two aluminum-coated strips attached. Striped cucumber beetle (Acalymma vittata Fabricius) and spotted cucumber beetle (Diabrotica undecimpunctata howardi Barber) (Coleoptera: Chrysomelidae) counts on yellow sticky cards were obtained over eight weekly samplings. For cucumber, on the peak beetle population date, there were six times as many striped cucumber beetles in solid black plastic mulch as in aluminum-coated plastic mulch, and nearly three times as many as in black plastic mulch with aluminum strips. For squash, both striped and spotted cucumber beetle counts were significantly higher on solid black plastic mulch on three peak sampling dates than on aluminum-coated plastic mulch and black plastic mulch with aluminum strips, with counts 4.9 to 5.5 times higher in solid black plastic mulch than in aluminum-coated plastic mulch, and 2.2 to 2.6 times higher than in black plastic mulch with aluminum strips. Using a threshold of 15 beetles/sticky card, no insecticidal applications were needed on solid aluminum-coated mulch, while an average of 1.8 insecticidal applications were needed on solid black plastic mulch, and 0.8 insecticidal applications on black plastic mulch with aluminum strips. The cost of solid black plastic mulch and its insecticidal applications, $186/acre ($459/ha), was $102/acre ($252/ha) less than the cost of aluminum-coated plastic mulch without insecticidal application, $288/acre ($711/ha). However, squash fruit from plants grown on aluminum-coated plastic mulch could be direct marketed as pesticide-free, at a price 25% higher than fruit on which pesticide had been applied. For an average yield in Virginia of 600 boxes/acre (1,482 boxes/ha) [20 lb/box (9 kg/box)] of squash, this translates to a $1,200/acre ($2,964/ha) increase in revenue. Yield on aluminum-coated plastic mulch was delayed by one week, but there were no significant differences in cumulative yield over 14 harvests.

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Chien Yi Wang

Methyl jasmonate (MJ) was applied to zucchini squash (Cucurbita pepo L.) fruit be pressure-infiltration (82.7 kPa for 3 min). Control fruit were similarly treated with distilled water. All fruit were then stored at a chilling temperature of 5C. Chilling injury occurred in the control fruit within 4 days of storage. However, the onset of chilling injury was significantly delayed by the MJ treatment. MJ-treated fruit also maintained higher levels of carbohydrates, while malic acid was the major organic acid. These constituents deteriorated slower in the MJ-treated fruit than in the control fruit.

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Richard G. Snyder, Frank Killebrew, and Joseph A. Fox

Yellow squash (Cucurbita pepo L.) planted after early spring in Mississippi have a strong likelihood of developing green streaks and blotches on the fruit-symptoms of watermelon mosaic virus strain 2. Cultivars with the relatively new precocious yellow gene (PYG) tend to show such symptoms less prominently, and in some cases not at all, when infected. Field trials were conducted at two locations to evaluate several PYG cultivars and compare their WMV-2 symptoms to those of standard, non-PYG types. In both cases, the PYG cultivars had fewer unmarketable fruit due to WMV-2 symptoms, although they were not entirely immune to the virus.

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Harry S. Paris

Most cultivars of acorn squash (Cucurbita pepo), such as `Table Queen', have fruit that are light green when young, become dark green by intermediate age, and remain dark green through maturity, carrying genotype D/D l-l/l-1 L-2/L-2. Many other forms of C. pepo that carry this genotype, the most familiar being the Halloween and pie pumpkins, turn orange at maturity. The genetic basis for green color retention of acorn squash was investigated by crossing `Table Queen' with `Vegetable Spaghetti', `Fordhook Zucchini', and accession 85k-9-107-2 (the parental, filial, backcross, and testcross generation progenies being grown out in the field and observed and scored for fruit color at maturity, between 40 and 44 days past anthesis). The results indicated that the three stocks crossed with `Table Queen' carry two recessive genes, designated mature orange-1 (mo-1) and mature orange-2 (mo-2), which act in concert to result in complete loss of green color before maturity in 1-1/1-1 plants. `Table Queen' is Mo-l/Mo-1 Mo-2∼o-2. Genes D and mo-2 are linked, ≈15 map units apart.

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D. Scott NeSmith

Different planting dates were used to study the influence of thermal time on leaf appearance rate of four summer squash (Cucurbita pepo L.) cultivars. During the first year (1991), thermal time or growing degree days (GDD) were calculated using a base temperature of 8C and a ceiling temperature of 32C for several planting dates. Leaf numbers per plant were determined every 2 to 3 days. Leaves that were beginning to unfold with a width of 2 cm or greater were included in the counts. The relationship between leaf number and GDD was established from the initial data set, and data from subsequent years were used for model validation. Results indicated that single equation could be used to predict leaf appearance of all four cultivars in response to thermal time. The response of leaf appearance to GDD was curvilinear, with a lag over the first five leaves. After five leaves, the increase in leaf number per plant was linear with increased GDD. Segmented regression with two linear functions also fit the data well. With this approach, leaf 5 was the node, and a separate linear function was used to predict the leaf number below five leaves and above five leaves. The results of this model should prove to be useful in developing a model of leaf area development, and eventually a crop growth model, for summer squash.

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Francisco Ramirez-Reyes and Sergio Garza-Ortega

Culture of the Gray Zucchini (GZ) variety of summer squash in northwestern Mexico during the fall is severely affected by a viral disease, which is apparently caused by squash leaf curl virus (SLQV). Resistance to this disease was introduced from local Cucurbita moschata landraces and uniform GZ-type lines and hybrids (GZLH) were developed. Crosses between lines were performed during Spring 1995. In the Fall, 21 GZLH plus the commercial materials PSR-59792, Raven, and GZ (usually included as a control) were studied. The commercial materials showed a higher degree of virus infection than GZLH. Four of the materials that showed symptoms of virus infection and one free of symptoms were tested for SLCV and all were positive for this virus. Eight GZLH had higher overall and 1× yields than GZ and nine and four GZLH were better than GZ for 2× and 3× yields, respectively. Number of stems varied from one to seven and stem and internode length had values from 42 to 145 cm and from 1.2 to 4.8 cm, respectively. These results were consistent with other similar studies previously reported.

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Nancy E. Roe, Peter J. Stoffella, and Herbert H. Bryan

Increasing disposal problems with polyethylene (PL) mulch and greater availability of compost prompted an investigation into the effects of using compost as a mulch on horizontal raised bed surfaces with living mulches (LMs) on vertical surfaces. Wood chips (WC), sewage sludge-yard trimming (SY) compost, and municipal solid waste (MW) compost were applied at 224 t·ha-1 on bed surfaces. Sod strips of `Jade' (JD) or `Floratam' (FT) St. Augustinegrass (Stenotaphrum secundatum Kuntze) or perennial peanut (Arachis glabrata Benth.) (PP) or seeds of a small, seed-propagated forage peanut (Arachis sp.) (SP) were established on the vertical sides of the raised beds before transplanting bell pepper (Capsicum annuum L.) into the beds. Phytophthora capsici reduced pepper plant stand in PL-mulched plots compared with organic mulch (OM) and LM. Despite the stand reduction, total pepper yields were highest in PL plots and, in the OM plots, decreased in the order SY > MW > WC. Early fruit yields and yield per plant were highest from plants in PL plots followed by SY. Among LMs, plants in SP plots produced highest early yields and FT produced the lowest. Plants in PL plots produced the largest fruit. When the same plots were seeded with winter (butternut) squash (Cucurbita pepo L.), plant stands were higher in MW than WC and SY. Squash yields were similar between PL and OM plots.

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Rosa Marina Arvayo-Ortiz, Sergio Garza-Ortega, and Elhadi M. Yahia

Winter squash are grown in northwestern Mexico for export to distant markets. During transport, fruits deteriorate and develop fungal rots. Squash (Cucurbita maxima Duch. `Delica') was given hot-water dips at 50C for 0, 3, 6, 9, and 12 min and stored at 10 and 20C with 75% RH for 4, 8, and 12 weeks. The highest weight loss (11.3%) was in fruits without hot water treatment stored at 20C for 12 weeks—weight losses were 3.6%, 7.2%, and 10.2% in the 4-, 8-, and 12-week storage periods, respectively. At 10C, the weight losses were 3.4%, 6.8%, and 7.6% for the same periods, respectively. ß-carotene content increased from 36.2 to 54.2 mg/100 g after 4 and 8 weeks of storage, respectively, but declined to 42.8 mg/100 g after 12 weeks. Chlorophyll content decreased as temperature and storage period increased, changing from 16.7 to 10.8 mg·liter-1 at 10 and 20C and from 16.9 to 15.8 mg·liter-1 and 8.8 mg·liter-1 at 4, 8, and 12 weeks, respectively. Fruits had decay caused by Rhizopus and Aspergillus. Weight loss, ß-carotene and chlorophyll contents, and decay were not affected by length of hot-water treatment. General appearance was better in fruits stored at 10 than at 20C.

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Rebecca Nelson Brown and James R. Myers

A molecular and morphological marker map would improve our knowledge of Cucurbita genetics, and would facilitate efforts to breed improved summer and winter squash cultivars. Random amplified polymorphic DNA (RAPD) markers were used to construct a partial map of the Cucurbita genome. The mapping population was the BC1 progeny of the Cucurbita pepo L. yellow straightneck inbred A0449 and the tropical Cucurbita moschata Duchesne ex Lam. landrace `Nigerian Local'. A0449 was the recurrent parent. This cross was chosen because of the relatively greater economic importance of summer squash, traits of value to be introgressed from the C. moschata parent, and maximized genetic variation from the interspecific cross. The map contains 148 RAPD markers in 28 linkage groups. Loci controlling five morphological traits were placed on the map. The map covers 1,954 cM, which is estimated to be 75% of the Cucurbita genome. The qualitative traits placed on the map include the B gene for fruit which turn yellow before anthesis, the M gene for silver mottling of leaves, and a locus controlling the intensity of rind color on mature fruit. Quantitative trait loci (QTL) associated with fruit shape and the depth of the indentations between primary leaf veins were identified.

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Vincent Russo

There is a question whether it is best to use synthetic or organic materials to fertilize horticultural crops. Fertilizer rate can effect nutritional value of banana squash (Curcubita maxima Duch.) which is used in processed food. Seed were planted in 1990, 1991 and 1992 into beds treated with recommended (base) and twice the recommended (2X) rates of synthetic or organic fertilizers. Lime was or was not first applied in spring 1991. Synthetic fertilizer produced better yields than organic fertilizer. In 1990, the base fertilizer rate improved yield. In 1992, the 2X fertilizer rate improved yield. Liming did not affect yield. Beginning soil pH was 5.55. For lime augmented treatments soil pH was increased to, and maintained at, 5.65 through fall 1992. For no-lime treatments soil pH was approximately 5.3 through fall 1992. Organic materials, likely bound to soil under acidic conditions, are less available and could explain lower yields. The data suggests that soil pH will have to be improved before banana squash yields can be increased using organic fertilizers.