2007 Extension Research Report
Insect Management
EFFICACY OF VENOM AND V-10170 APPLIED THROUGH DRIP
IRRIGATION SYSTEM FOR MANAGEMENT OF SILVERLEAF IN
SQUASH
Alton N. Sparks, Jr., University of Georgia Cooperative Extension, Department of Entomology, Tifton,
GA 31793, asparks@uga.edu
of silverleaf were noted the day of application.
These applications were applied through drip
irrigation lines placed next to the plants (adjacent
to the irrigation lines). An injection manifold was
designed for this test to apply a single treatment to
all four replications at one time. The manifold had
a single injection port followed by a ‘mixing’
assembly (two 90 degree turns) followed by Tconnections leading to 4 solid injection lines
(approximately 200 feet each). The injection lines
were attached to 33 feet of drip tape. The drip tape
was placed next to the plants of the specified plots
for treatment. Once the tape was in place for all
four plots of a treatment, the irrigation water was
turned on and the system allowed to pressurize
and run for approximately 5 minutes (and was
checked for any leaks). The specified treatment
(for all four plots) mixed in 3 liters of water was
then injected into the running system. This
required approximately 5 minutes to complete the
injection. After injection of the treatment, the
system was allowed to run for an additional 10
minutes to insure the full treatment was flushed
from the irrigation lines and into the plots. The
irrigation was then turned off and the lines were
moved to the next set of plots and the process was
repeated. After all treatments were applied, this
system was set on the check plots and run for 20
minutes to insure equal moisture in the check
treatment.
Efficacy was evaluated by rating
silverleaf symptom severity and yield in each plot.
Plots were visually examined and rated on the
amount and distribution of silverleaf symptoms as
follows:
0 = no silverleaf
Introduction
The sweetpotato whitefly (a.k.a. silverleaf
whitefly) can be a severe pest in Fall vegetable
production in some areas of south Georgia. This
pest is of particular concern in squash, where even
low populations cause silverleaf symptoms.
Neonicotinoid insecticides play a key role in
managing this problem. Soil application of these
products typically provides long residual control.
This test was conducted to evaluate the efficacy
and residual control of soil applied insecticides
for management of silverleaf in squash.
Materials and Methods
A small plot trial was conducted at the
University of Georgia Horticulture Farm in
Tifton, Georgia. Squash, var. Destiny III, was
direct seeded in single rows on six foot beds for
this test on 7 Aug., 2006. Drip tape was
immediately set on the rows to maintain adequate
moisture for plant establishment and for irrigation
during the season. After plant establishment,
experimental plots measuring one row (assumed
36 inch for treatment calculations) by 33 feet were
established in a randomized complete block
design..
Treatments evaluated in the test were V10170 50 WD at 3 and 6 oz/ac, Venom 70SG at
7.5 oz/ac, and combination treatments of Venom
at 7.5 oz/ac plus V-10170 at 3 and 6 oz/ac. These
treatments were compared with Admire Pro 4.6F
at 7.4 oz/ac and a non-treated control.
All insecticides were applied through drip
irrigation simulation. Insecticides applied through
the drip system were applied on 15 Aug. Plants
were well established at this time. Minimal signs
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1 = light symptoms and spotty
distribution within the plot
2 = light symptoms throughout the plot,
or moderate symptoms and spotty
3 = moderate symptoms and even
distribution
4 = heavy symptoms and spotty
distribution
5 = heavy symptoms throughout the plot
Yields were determined by hand harvesting each
plot. On each harvest date, each plot was hand
picked, with the entire plot picked. Fruit from
each plot were counted and weighed. All data
were analyzed with the PROC ANOVA procedure
of PC-SAS. Where significant differences were
detected (P<0.05), means were separated with
LSD (P=0.05).
performance of Admire in this tests is of concern.
This may have resulted from the application
technique (drip line on the soil surface and
exposure to sunlight), but may also represent
potential resistance development to the
neonicotinoid insecticides. Even though Venom
provided significant control in this test, it should
be noted that silverleaf symptoms had increased in
all treatments between 24 and 29 Aug. and the test
was terminated after only two harvests because of
overall poor condition of the plants. The 29 Aug.
sample date was only 14 days after treatment, and
both the Admire and Venom would be expected to
provide at least 3 to 4 weeks of protection at the
rates used. The lack of control may have also
occurred because of the severe pest pressure;
however, silverleaf is reported to result only from
immature whiteflies. Silverleaf symptoms
appearing at 14 days after treatment would
suggest reproduction and survival of immatures
within two weeks of treatment, which should not
occur with either of these products under any level
of pest pressure.
Results and Discussion
Pest pressure was extremely heavy in this
test. The only treatments that statistically
separated from the Check in the test were the
three treatments that contained Venom (Table 1).
Addition of V-10170 did not appear to improve
performance of Venom. The relatively poor
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