EFFICACY OF RANMAN AND OTHER PRODUCTS IN CONTROL OF
PHYTOPHTHORA CAPSICI IN SQUASH AND BELL PEPPER
Pingsheng Ji, A. S. Csinos, L. L. Hickman, J. McMillan, and U. Hargett, Department of Plant Pathology,
Coastal Plain Experiment Station, University of Georgia, P.O. Box 748, Tifton, GA 31793
Introduction
Phytophthora blight caused by Phytophthora capsici is responsible for serious losses in the
production of cucurbits, peppers, and several other vegetable crops in Georgia. The disease is among the
most difficult to control and the efficacy of current strategies for management of this disease is limited.
Cultural practices such as using well-drained soils with raised beds help reduce the disease but not enough
to prevent disease outbreaks when weather conditions are favorable for the pathogen. Development of
integrated approaches using chemicals, biologicals, and cultural practices may improve disease control.
This study was to evaluate the effectiveness of several chemical fungicides for control of P. capsici on
squash and bell pepper.
Materials and Methods
The experiment was conducted at University of Georgia Coastal Plain Experiment Station (Black
Shank Farm) located in Tifton, GA. The field site has been used as a P. capsici nursery and was
inoculated with the pathogen. Raised beds were prepared for plant growth that were 6-inch-high by 30inch-wide and centered 6 feet apart. Yellow squash (cv. Gentry) and bell pepper (cv. Plato) seedlings
were transplanted at 12 inch spacing within a row into raised beds on April 11. The experimental plots
consisted of a single row which was 15 feet long. Buffer zones with 4 feet spacing without planting of
crops were maintained between plots. A randomized complete block design was employed with four
replications.
Ranman, Omega and other products were applied at the rates as described in Table 1. Nontreated plots and Ridomil Gold treatment were used as controls. Plants with Phytophthora blight were
counted weekly after first appearance of symptoms in the field. Squash fruit were hand harvested on May
14, 21, 25, 30 and June 14 and bell pepper fruit were harvested on June 14. Marketable and unmarketable
yields were determined and the number of P. capsici infected fruit was recorded. Analysis of variance
(ANOVA) was used to determine the effect of the treatments on disease incidence and yield using the
Statistical Analysis System (SAS Institute, Cary, NC).
Results and Discussion
The squash cultivar Gentry was susceptible to Phytophthora blight and the final disease incidence
reached 70% (infected plants) in the non-treated control plots (Table 1). Application of Omega in
conjunction with Ranman provided 45% disease reduction compared with the non-treated control though
this reduction was not statistically significant. All the treatments reduced disease incidence numerically
compared to the non-treated control (Table 1).
Final disease incidence on bell pepper reached 56% (infected plants) in the non-treated control
plots. Application of Ranman in conjunction with Kocide resulted in a 53% disease reduction, compared
to the non-treated control, based on the final percentage of infested plants. But none of the treatments
provided significant disease suppression.
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Table 1. Efficacy of Ranman and other products in control of Phytophthora blight
Disease (squash)
Treatment and rate
Non-treated control
Ranman, 2.75 fl. oz/A
Ranman, 2.75 fl. oz/A +
Silwet, 2.0 oz/A +
Kocide 2000, 1.5 lb/A
Omega, 1.5 pt/A
Omega, 1 pt/A
Ranman, 2.75 fl. oz/A
K-Phite
Ridomil Gold, 2 pt/A
Application schedule
At transplant
spray
Disease (pepper)
Infected
fruit1,2
Infected
plant 1,3
Infected
fruit1,2
Infected
plant1,3
9.8 b
70.0 a
9.5 b
56.3 ab
23.0 a
55.0 a
22.5 a
26.6 b
24.0 a
38.4 a
24.0 a
43.8 ab
9.5 b
65.0 a
9.0 b
71.9 a
17.3 ab
46.7 a
16.8 ab
48.4 ab
directed
Directed spray every two
weeks
At transplant directed
spray
At two weeks post plant
At 30 days PHI (preharvest interval)
At transplant directed
spray
Directed spray every two
weeks
At transplant
At two weeks post plant
At 30 days PHI
1
Data are means of four replications. Means within a column followed by the same letter are not
significantly different (P = 0.05) according to Duncan’s multiple range test.
2
Number of P. capsici infected fruit each plot.
3
Final disease incidence (% infected plant).
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