CHEMICAL CONTROL OF
POWDERY MILDEW ON PUMPKIN, 1999
PUMPKIN
(Cucurbita pepo 'ProGold 500')
Powdery
mildew; Sphaerotheca fuliginea
R.
M. Riedel,
Rebecca
Lyon,
Gretchen
Sutton
Mark
Schmittgen
Department of Plant Pathology,
Department
of Horticulture & Crop Science
The
Ohio State University
Columbus,
OH 43210
CHEMICAL CONTROL
OF POWDERY MILDEW ON PUMPKIN, 1999:
Plots were established on Crosby silt loam (pH 6.5, OM < 2%) at the
Waterman Farm, Ohio State University,
Columbus, OH (Franklin Co.). Pumpkins were seeded 10 ft apart in single 30 ft
rows on 15 Jun. Treatments were replicated 4 times in a randomized complete
block design. Plots received 80 N lb/A and Curbit 3E 3pt/A preplant. Fungicides were applied at 65 psi and 60
gal/A using a gasoline-powered, tractor-mounted sprayer with a one-row boom
carrying 5 Delavan HC-8 tips. Foliage was rated for Powdery Mildew development
on 30 Aug. Fruit stems (handles) were
rated for Powdery Mildew at the same time.
Fruit was harvested from 30 ft of row for each plot on 21 Sept and
sorted into Orange, Green and Cull categories. Rainfall for Jun, Jul, Aug, and
Sept was 1.65, 2.78, 2.61 and 1.15 in., respectively.
Powdery Mildew
was first observed in the plots on 5 Aug.
Development was severe. Virus
symptoms were severe by early September. The season was quite dry and the crop
was grown without irrigation. Yield was low, consequently, with highest yields
of orange fruit being only 8.9 ton/A, about half of normal yield for this
variety. There was a great deal of variability in fruit set within the test
plot.
All chemical
treatments were similar to check in terms of yield of orange fruit. Yield tended to increase as Powdery Mildew
control increased, but there were no significant differences between treatments
or between treatments and check. Flint
had significantly more green fruit than check or other fungicide treatments;
perhaps because of excellent powdery mildew control with this material
contributed to continual vine growth.
In terms of control of foliar symptoms of Powdery Mildew, all fungicide
treatments were significantly better than check except for programs
containing Cinnamite, Microthiol or Dithane.
Table 1:
Control of Disease on Pumpkin cv. ProGold, 1999; Columbus, OH
Treatments Orange[1] Green[2] Cull[3] Foliar
Rating[4]
CHECK 83.8a
0.0 b 2.9ab 100.0a
Bravo
Ultrex 2.7lb/A (D,E,F)* 89.6a 0.0 b 11.2a 50.0 bc
+Benlate
1lb/A
Microthiol 4lb/A (D,E,F) 99.6a 0.7
b 0.0 b 75.0a
Cinnamite 85floz/A (D,E) 107.9a 0.0 b 1.4ab 100.0a
Bravo Ultrex 2.7lb/A (F)
Dithane 2lb/A (D,E,F) 83.7a 0.0
b 8.6ab 93.8a
Nova
0.16lb/A (A,B,C,D,E,F) 122.9a 0.0
b 5.9ab 43.8 c
+Bravo
Ultrex 2.7lb/A
Flint 50WG 3.0oz/A (D,E,F) 120.2a 7.2a 4.8ab 12.5
d
Bravo Ultrex 2.7lb/A
Quadris 0.3834pt/A (D,F) 122.9a 1.3 b 5.6ab 62.5 bc
Bravo Ultrex 1.8lb/A (E)
Bravo
Ultrex 2.7lb/A (D,E,F) 120.8a 1.1 b 1.1ab
68.8 bc
+Folicur
6oz/A
+B1956
.06%
VALUES FOLLOWED BY SIMILAR LETTERS ARE NOT SIGNIFICANTLY
DIFFERENT BY DUNCAN MULTIPLE RANGE TEST.
1. ORANGE = MARKETABLE ORANGE FRUIT; Lb/30ft of row
2. GREEN = MARKETABLE GREEN FRUIT; Lb/30ft of row
3. CULL = NON-MARKETABLE FRUIT WITHOUT DISEASE; Lb./30ft of
row
4.Percent of Powdery Mildew on the Foliage
BOLD
= Tank mix
* =Application dates: A=27 Jul; B=3 Aug; C=10 Aug; D=17 Aug;
E=31 Aug; F=9 Sep.
Plant date: 15 Jun 1999
Harvest date: 21 Sep 1999
Rate date: 30 Aug 1999
