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Evaluation of Fungicides and a Tolerant Cultivar with an IPM program for Control of
Foliar and Fruit Diseases of Pumpkins, 1999

Win Cowgill, T.Hausamann, K. Holmstrom, M. Maletta, S.A. Johnston, P. Nitzsche

Rutgers Cooperative Extension
Extension Center, 4 Gauntt Place
Flemington, NJ 08822

Fungicide applications are one of the highest costs in the pumpkin production system for
growers in New Jersey. The objective of this study were(1) to develop cost-effective strategies for
controlling powdery mildew in pumpkins using IPM strategies, powdery mildew tolerant varieties and
lower cost fungicide combinations; (2) to determine an effective resistance management strategy for
new fungicides used to control powdery mildew; and (3) to validate pest management thresholds and
scouting procedures to develop a scouting program for New Jersey pumpkin growers. Methods: At
the Rutgers Snyder Research and Extension Farm in Pittstown, NJ, two fields with no prior history of
cucurbit production were used for this experiment. The soil was a Quakertown silt loam with a pH of
6.5. On 18 May, both fields werechisel plowed. A broadcast application of 250 lb/A of 20-10-10
(N-P-K) and 120 lb/A of 0-0-50 (N-P-K) was incorporated on field A, and 250 lb/A of 20-10-10 (N-
P-K) and 220 lb/A of 0-0-50 (N-P-K) on field B on 22 Jun. A standard seedbed was prepared (disked
then harrowed) on 23 Jun, and Prefar at 5 qt/A was disked in at this time for weed control. On 25 Jun,
pumpkins were hand seeded at five seeds per hill, spaced 2-ft apart in each single row replication.
Immediately following, Furadan 4F at 3.8 oz/A and Command 3 ME at 8 oz/A were applied to all plots
and then irrigated in for management of cucumber beetles and weeds, respectively. Plants were thinned
to two per hill on 15 Jul. On 21 Jul, Permit at 1 pt/A was broadcast to control pigweed. Rainfall was
0.77 in. in Jun, 2.63 in. in Aug, 13.62 in. in Sep, and 3.17 in. in Oct. Each field was irrigated with an
overhead retractable gun on 25 Jun, 29 Jun, 6 Jul, 12 Jul, 23 Jul, 27 Jul, 4 Aug, 11 Aug, and 3 Sept,
for a total of 9 times (1.0 in./application). Plots consisted of a single, 10-ft-long row on 10-ft centers
with a 10-ft fallow area present on all sides of each plot. Treatments were replicated 4 times in a
randomized complete block design. Fungicide treatments were applied with a tractor mounted
Norwesco sprayer containing a 30 gallon tank, and an offset boom utilizing TXA8004VK cone
nozzles placed 20 in. apart. The sprayer delivered 63 gal/A at 60 psi. A powdery mildew (PM)
susceptible cultivar , 'Jackpot', and a PM tolerant cultivar, 'Magic Lantern', were utilized to evaluate
their performance in conjunction with an IPM threshold initiated spray program (plots scouted weekly,
and fungicide application initiated once 1 PM lesion is detected on 50 older leaves).Using a
conventional spray program on 'Jackpot', fungicide treatments were initiated at first runner on 2 Aug
and repeated every 7-10 days thereafter, ending with a total of 9 applications. Approximately two
weeks later, on 13 Aug, IPM threshold initiated treatments began on the 'Jackpot' IPM plots after
detecting a threshold level of infection of PM. Once initiated sprays were applied on 7-10 day calendar
schedule resulting in 7 total applications. Only an IPM initiated spray schedule was used with 'Magic
Lantern'. On 22 Aug, IPM threshold initiated treatments began, and were repeated every 7-10 days
thereafter resulting in 6 total applications. Pumpkins were visually rated for defoliation as a result of
infection from powdery mildew on 23 Sep. On 12 Oct, each plot was harvested and fruit weighed. On
the same day, fruit were evaluated for handle condition.

Results: Using an IPM initiated spray schedule on 'Jackpot', two less fungicide
applications were made in comparison to conventional schedule on the same variety. With 'Magic
Lantern' the IPM threshold initiated spray schedule resulted three less fungicide applications than the
conventional schedule with 'Jackpot'. The incidence of PM was high in this test, and the test was
considered to be definitive. All fungicide treatments on 'Jackpot', except for Champ + Maneb on an
IPM initiated schedule resulted in less foliar disease than the untreated 'Jackpot' treatment. All
fungicide treatments on 'Magic Lantern' had significantly better foliar diseasecontrol than the
untreated 'Magic Lantern'. There were no significant differences in marketable yield among all 'Magic

1999 North Jersey Tree Fruit Annual Report