2007 Extension Research Report
Disease Management
CHEMICAL MANAGEMENT OF PHYTOPHTHORA BLIGHT OF
SQUASH
B. L. Candole, Lara Hickman, A. S. Csinos, and Unessee Hargett,Department of Plant Pathology,
University of Georgia, Coastal Plain Experiment Station,P. O. Box 748,Tifton, GA 31793
were obtained on April 20, 2006. Incidence of P.
capsici infection was collected weekly until the
last harvest.
Introduction
Phytophthora blight caused by
Phytophthora capsici is one of the most
destructive diseases of a number of vegetable
crops. Summer squash is highly susceptible to
crown and fruit rot. Plant death occurs
immediately after initial infection of the growing
portion (crown) of squash plants. Fruit infection
occurs as sunken, dark, water-soaked areas which
are covered with white fungal growth. Under
conditions conducive to disease development, P.
capsici can kill the entire squash plantings. This
test evaluated several chemicals either alone or in
combination with other chemicals under
plasticulture.
Results and Discussion
None of the treatments were significantly
different than the untreated control in terms of
marketable yield and the number of
nonmarketable fruits (Table 2). Of the 7
treatments, trends in marketable, nonmarketable
and total yields were lowest in plants treated with
Ridomil Gold Copper 65 WP plus Maneb 75 WP.
Further trends observed among treatments was
that although A14576 plus NIS (Activate Plus or
Induce) plus Ridomil Gold Copper 65 WP-treated
plants (Treatment No. 6) yielded the highest
weight of marketable and total fruit yields they
also yielded the highest nonmarketable fruit
weight. The same treatment also yielded a
significantly higher nonmarketable fruit weight
than the untreated control.
Plants treated with A14576 plus NIS
(Activate Plus or Induce) plus Ridomil Gold
Copper 65 WP (Treatment No. 6) have the lowest
incidence of Phytophthora blight which was
significantly lower than the untreated control.
Fruit rot incidence from the same treatment was
also the lowest among 7 treatments but was not
significantly lower than the untreated control.
In summary, Treatment No. 6 (A14576
plus NIS [Activate Plus or Induce] plus Ridomil
Gold Copper 65 WP) resulted in lower
Phytophthora blight incidence, lower fruit rot
incidence and possibly higher (fruit weight)
marketable yield.
Materials and Methods
The test was performed under
plasticulture at the Black Shank Farm of the
University of Georgia’s Coastal Plain Experiment
Station, Tifton, GA in the spring of 2006.
Summer squash cv. Prelude II was transplanted on
April 12, 2006. Foliar applications of the
chemicals were started on April 13, 2006. Land
was prepared according to the guidelines
recommended by the Georgia Cooperative
Extension Service. The treatments (Table 1) were
arranged in a randomized complete block design
(RCBD) with 5 replications. Each plot was
inoculated the day after transplanting by placing
15-20 beet seeds in three locations in each plot
just below the soil surface. An irrigation regime
was employed during the trial to create a
conducive environment for disease development.
Initial plant populations per plot or per treatment
62
Table 1. Treatments and frequency of treatment applications.
Treatment and rate of application
Application rate
Application frequency
-
-
1. Untreated check
a
b
2. 1 Ridomil Gold Copper 65 WP
2 Maneb 75 WP
2.5 lb/A
2 lb/A
1 every 14 days (foliar) - APa (4
times)
1 every 14 days (foliar) - PPb (4 times)
3. 1 Acrobat 50 WP
2 Maneb 75 WP
3 Maneb 75 WP
6.4 oz/A
2 lb/A
2 lb/A
1 every 14 days - APa (4 times)
1 every 14 days - APa (4 times)
1 every 14 days - PPb (3 times)
4. 1 Tanos 50 WG
1 Kocide 2000 53.8 DF
2 Maneb 75 WP
10 oz/A
2 lb/A
2 lb/A
1 every 14 days - APa (4 times)
1 every 14 days - APa (4 times)
1 every 14 days - PPb (3 times)
5. 1 Mandipropamid
1 NIS (Activate Plus or Induce)
2 Ridomil Gold Copper 65 WP
8.2 floz/A
1 every 14 days - APa (4 times)
1 every 14 days - APa (4 times)
1 every 14 days - PPb (3 times)
6. 1 A14576
2 NIS (Activate Plus or Induce)
3 Ridomil Gold Copper 65 WP
6.84 floz/A
7. 1 Mandipropamid
1 NIS
1 Maneb 75 WP
2 Ridomil Gold Copper 65 WP
8.2 floz/A
2.5 lb/A
2.5 lb/A
2 lb/A
2.5 lb/A
AP = beginning at planting.
PP = beginning 1 week after planting of post plant.
63
1 every 14 days - APa (4 times)
1 every 14 days - APa (4 times)
1 every 14 days - PPb (3 times)
1 every 14 days - APa (4 times)
1 every 14 days - APa (4 times)
1 every 14 days - APa (4 times)
1 every 14 days - PPb (3 times)
Table 2. Efficacy of mandipropamid against phytophthora blight of squash (cv. Prelude II). Spring, 2006.
Marketable yield
a
Nonmarketable yield a
(cull)
Total yield a
Phytophthora
blight
incidence
(%)
Fruit rot (due
to P. capsici)
incidence
(%)
Number/A
lbs/A
Number/A
lbs/A
Total
number/A
Total
weight
(lbs/A)
1. Untreated check
32,482 a
17,912 a
15,112 a
2,407.00 b
47,594 ab
20,319 b
77.56a
34.14 ab
2. 1 Ridomil Gold Copper 65 W P - 2.5 lb/A
2 Maneb 75 WP - 2 lb/
30,310 a
17,333 a
9,406 a
2,222.9 b
43,999 ab
19,555 b
70.22 a
37.32 ab
3. 1 Acrobat 50 W P - 6.4 oz/A
2 Maneb 75 W P - 2 lb/A
3 Maneb 75 W P - 2 lb/A
38,606 a
20,268 a
14,121 a
2,442.4 b
52,727 a
22,711 ab
52.46 ab
30.31 ab
4. 1 Tanos 50 W G - 10 oz/A
1 Kocide 2000 53.8 DF - 2 lb/A
2 Maneb 75 W P - 2 lb/A
32,383 a
19,347 a
11,616 a
3,571.50 ab
39,716 b
22,919 ab
46.90 ab
46.57 a
5. 1 Mandipropamid - 8.2 floz/A
1 NIS (Activate Plus or Induce)
2 Ridomil Gold Copper 65 W P - 2.5 lb/A
32,130 a
19,755 a
16,525 a
3,101.8 ab
48,656 ab
22,856 ab
65.34 a
32.93 ab
6. 1 A14576 - 6.84 floz/A
2 NIS (Activate Plus or Induce)
3 Ridomil Gold Copper 65 W P -2.5 lb/A
37,429 a
22,711 a
14,594 a
4,581.40 a
52,0232 a
27,293 a
21.64 b
27.03 b
30,626 a
20,975a
16,972 a
3,730.80 ab
47,598 ab
24,706 ab
54.54 ab
30.86 ab
Treatment
7. 1
1
1
2
a
Disease a
Mandipropamid - 8.2 floz/A
NIS
Maneb 75 W P - 2 lb/A
Ridomil Gold Copper 65 W P - 2.5 lb/A
Numbers are means of 5 replications. W ithin a column, means followed by the same letters are not significantly different by means of LSD (P = 0.05).
64