Ohio produces over 3000 acres of pumpkins with much of the crop shipped to the wholesale market. Many small enterprises generate significant additional income from pumpkins which may be as high as 30-40% of their gross income. Despite the crop's value, many growers ponder whether they should commit much money to a pest control program. Economically important diseases include: powdery mildew, numerous mosaic viruses and bacterial wilt that attack pumpkins and can cause as much as a 20-50% reduction in yield and quality. Powdery mildew attacks every year and rapidly defoliates vines. Bacterial wilt spread by cucumber beetles is usually prevented by Furadan but many small growers are not licensed to use this restricted use pesticide. Over the past 3 years, two thirds of Ohio has had significant losses of pumpkins due to various mosaic viruses. Practical alternative strategies are now required to control the array of pests that attack pumpkins.

The objectives for this study were: 1. To compare chemical and alternative fungicides for control of powdery mildew and 2. To evaluate physical barriers such as P10 row covers for aphid and beetle control, straw mulch for fruit rot control and reflective mulch for aphid control and traditional chemical protection methodology for control of cucumber beetles, bacterial wilt, aphids and mosaic virus.

Plots were established at the Horticultural Research Farm, The Ohio State University, Columbus, OH (Franklin Co.) and at a farm near Springfield, OH (Clark Co.). In Springfield, fungicide plots consisted of single 40 ft rows of pumpkins and insect control plots were 5 rows. In all Springfield plots, pumpkins were seeded one ft apart in the row on 17 June. Rows were 8 ft apart. In Columbus, pumpkins were seeded 8 June in hills 3 ft apart in single 40 ft rows, 10 ft apart for both fungicide and insect control plots. Reflective mulch was not included in the single row plot at Columbus. All treatments were replicated 4 times in a randomized complete block design.

CHEMICAL CONTROL OF POWDERY MILDEW ON PUMPKIN, Columbus: Pumpkins were harvested 21 September and graded into cull and marketable categories. Foliage was rated for powdery mildew development on 2 and 21 September. Powdery mildew was first observed in the plots on 29 July (see Table 1). Disease development was rapid and severe. Following the second application of irrigation water, a new flush of vine growth occurred. Anthracnose lesions were common on the foliage in early July. Dry weather in late summer suppressed Anthracnose development. Nova, RH 0611, ASC 66902 and Bravo +Benlate treatments controlled foliar damage significantly better than check at both rating dates. The two unconventional materials, Kasil and oil + sodium bicarbonate, did not significantly reduce foliar damage. None of the treatments significantly affected total weight of usable harvest of pumpkin fruit.

Fruit Rots: In Columbus and Springfield, straw mulch did not affect the quantity or weight of cull fruit. The side of the fruit laying on the straw developed enlarged lenticels (scar tissue) rendering most fruit unusable.

In Columbus, there was no significant effect of fungicide and insect control treatments on yield of marketable fruit. Only Adios alone for insect control and Bravo + Benlate alone for disease control produced fruit significantly larger in size than other treatments.

CHEMICAL CONTROL OF POWDERY MILDEW ON PUMPKIN, Springfield, OH: Plots were established on 17 June. Pumpkins were harvested 29 September and graded as cull, marketable with good handles or marketable with bad handles. Foliage was rated for powdery mildew development on 26 August and 17 September. Powdery mildew was first observed in the plots on 28 July. Disease development was rapid and severe. All fungicide treatments controlled foliar damage significantly better than check at the first rating (see Table 2). At the second rating, all treatments except Kasile #6 and spray oil + sodium bicarbonate controlled Powdery Mildew better than check. None of the fungicide treatments were better than check in terms of tons of usable harvest/A. ASC 66902 treatments gave significantly better handle quality than control

CONTROL OF ZUCCHINI YELLOWS MOSAIC IN PUMPKIN, 1993: Treatments in Springfield consisted of an untreated control, standard pesticide (Furadan 15G + Sevin ), reflective mulch + Furadan 15G, row cover (aphid and cucumber beetle control) and Adios (cucumber beetle control). Alanap 2L (naptalam) 4 qt/A plus Prefar 4E (bensulide) 2 qt/A were applied preemergence for weed control. Silver colored, 5 ft wide reflective mulch was laid by hand prior to planting and seed was planted through punched holes. Row cover plots were covered immediately after planting with Agryl P10, 8 ft wide, light weight row cover material. Row Covers were removed at the time of flowering on 22 July. Standard and reflective mulch plots received Furadan 15G at planting, 2 foliar applications of Sevin XLR, 1 application of Bravo 720 and 1 application of Benlate 50DF. Row cover plots received all pesticide treatments except Furadan. Pumpkins were harvested 30 September and graded as virus infected and marketable fruit. Two inches of water was added to the plots by overhead irrigation in mid-August.

Foliage and fruit with symptoms of zucchini yellows mosaic (ZYM) were observed by the third week of July. At harvest, ZYM was common in the plots. Infection averaged 22% of the total yield and ranged from 12 to 40%. Incidence of virus infected fruit was lowest in reflective mulch plots (see Table 3), but no treatments differed significantly from control. Infected fruit wt in reflective mulch treatments was significantly lower than plots with row covers. There were no significant differences in infected fruit number, marketable yield and average fruit size. No bacterial wilt or beetle feeding on fruit were detected.

Extension Program Implementation:

A pumpkin twilight meeting was held on 23 August 1993 in cooperation with Clark and Greene County Extension. Approximately 50 growers were in attendance from several southwestern and western counties of Ohio. Powdery mildew, insect and disease control strategies were presented to the audience. Later, specialists held individual consultations and plot tours.

Results of the project will be shared with growers at the Washington/Meigs Vegetable school, the Annual Muck Crops school and the 1994 Ohio Fruit and Vegetable Congress. Final reports will be printed for distribution at winter meetings and in extension bulletins on pumpkin production. These data will serve as a basis for developing reduced input strategies.

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