2007 Extension Research Report
Disease Management
EFFICACY OF FUNGICIDES AGAINST PHYTOPHTHORA CAPSICI OF PEPPERS
A. S. Csinos and B. L. Candole, Department of Plant Pathology, University of Georgia Coastal Plain
Experiment Station, P. O. Box 748, Tifton, GA 31793
of Georgia’s Coastal Plain Experiment Station, in
Tift county, Georgia. Pepper seedlings (cv.
‘Aristotle’) were transplanted in August 15, 2006
in a double row configuration on bare ground
plots measuring 30 ft long and 5 ft wide. Within a
row, pepper plants were 12 in apart and rows
within a plot were 24 in apart. Pepper plants were
maintained according to the guidelines
recommended by the Georgia Cooperative
Extension service. Each plot was inoculated (500
cm3 3-wk-old culture in vermiculite-V8 medium +
500 cm3 sterile sand per plot) one day before
transplanting. The upper 2 in of the inoculated
plots were roto-tilled to mix the inoculum with the
soil thoroughly.
The treatments were arranged in a
randomized complete block design (RCBD) with
four replications. Basal drench application at
transplanting were made by spraying to within 6
in circle around the base of the plant until desired
amount has been sprayed. Later sprays were
directed towards the entire plant and within the
crop canopy by using CO2 -pressurized back at 50
gal/A to simulate air blast equipment. Foliar
sprays started approximately 14 days after
transplanting and then on a weekly basis
according to the protocol for a total of seven
sprays. Disease evaluation included incidence of
dead plants, percentage of plants with infected
stems and yield data. Statistical analyses were
performed by means of analysis of variance and
mean separation by means of the least significant
difference test (P=0.05).
Introduction
Phytophthora capsici has been an
endemic problem to vegetable production in
Georgia since it was first observed in multiple
locations in the Fall of 1994. P. capsici has a
wide host range that includes solanaceous crops
(tomato, eggplant and peppers), cucurbits
(cucumber, watermelon, pumpkin and squash) as
well as cocoa and macadamia. On pepper, the
pathogen infects seedlings and mature plants and
has the potential for rapid polycyclic disease
development from a limited amount of initial
inoculum. Stems, roots, leaves and fruits may be
attacked by the pathogen which could lead to
blighting of the entire plants in just a few days.
Existing measures if any to control this disease are
variable in activity and the best of
recommendations may fail under high disease
pressure. Breeding for resistance against P.
capsici is difficult because the genetics of host
resistance of peppers to this pathogen has not
been characterized. Furthermore, no effective
chemicals are currently labeled for the control of
this disease, and recommended control practices
have had only limited success. Mefenoxam,
labeled for use on cucurbits against Pythium spp.,
is also effective in Georgia and is used to manage
Phytophthora blight. However, there is a strong
risk of the development of resistance to
mefenoxam by P. capsici due to mefenoxam’s
specific mode of action. Thus, alternative
products are needed by Georgia’s growers for this
important disease problem. Therefore, the
objective of this study is to test new chemicals for
efficacy against P. capsici in pepper.
Results and Discussion
Conditions were not favorable for
Pytophthora blight even though wet condition was
maintained by sprinkler irrigation twice a day.
Hence, only seedling damping-off was observed
Materials and Methods
The test was conducted in the P. capsici
nursery at the Black Shank Farm of the University
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as early as one week after transplanting and plants
with black stem lesions were observed late in the
season. Except for V-10161 or Ranman, the
percentage of dead plants and the disease
incidence in terms of AUDPC were not
significantly different than the untreated control
or the Ridomil standard (Table 1). While the
incidence of dead plants and AUDPC value in V10161-treated plants were the lowest, they also
had the lowest yield among the eight treatments
(Table 1). Furthermore. the incidence of dead
plants and AUDPC values in V-10161-treated
plants were significantly lower than the values in
the untreated plants but the differences in yield
between these two treatments were not significant.
Due to the absence of significant differences
among treatments, and between chemical
treatments and the untreated control, the
conclusion as to which of the test chemicals was
the most effective against P. capsici is not
warranted.
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Table 1. The effect of selected chemicals on the incidence of dead plants due to Phytophthora
capsici, areas under the disease progress curves (AUDPCs) and yield of pepper (cv. ‘Aristotle’).
AUDPCb
Total fruit
yield
(t/ha)
14.2 ab
1532 a
2.8 cd
2.5 bc
8.0 b
801 ab
3.4 bcd
2.8 abc
20.3 a
1275 ab
4.1 ab
3.9 ab
7.8 b
748 b
2.5 d
2.3 c
Maestro 80 DF (Arysta/MANA) = 6 lb/A.
Basal drenched at transplanting then foliar
sprays.
11.3 ab
854 ab
4.1 abc
3.2 abc
Folpan 80 WDG (Folpet, MANA) = 6 lb/A.
Basal drenched at transplanting then foliar
sprays.
13.5 ab
1096 ab
3.3 bcd
2.9 abc
10.5 ab
963 ab
3.7 abcd
3.5 abc
Treatment
Untreated
Dead
plants
(%)a
Marketable
yield t/ha
Ranman (Cyazofamid) = 2.75 fl oz/A. Basal
drenched at transplanting.
Raman + Silwet L-77 = 2.75 + 2 fl oz/A.
Foliar sprays.
SA-110201 10%SC (Sipcam) - 32 fl oz/A.
Basal drenched at transplanting then foliar
sprays.
V10161 (Fluopicolide) = 40 g ai/A. Basal
drenched at transplanting then foliar sprays.
NOA 446510 250 SC (Mandipropramid) = 8
fl oz/A. Basal drenched at transplanting .
NOA 446510 250 SC + Nonionic surfactant =
8 fl oz/A (0.125%). Foliar sprays.
Ridomil Gold EC (Mefenoxam) = 1 pt/A. Preplant soil incorporation & drench/basal spray
30 days later.
13.9 ab 1003 ab
4.8 a
4.1 a
Ridomil Gold/MZ (Mefenoxam) = 2.5 lbs/A.
Foliar spray.
Numbers are averages of 4 replicates.
a
Dead plants (%) = (number of dead plants/total number of plants) x 100.
b
AUDPC = n 3i = 1 (Xi+1 + Xi)(ti+1 -ti)/2, where Xi = disease incidence at the ith observation, ti = days at the
ith observation, and n=total number of observations.
Within a column, numbers followed by the same letters are not significantly different by LSD at p=0.05.
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