The Effect of
Clinch™ on Ants Common to Northern California Almond Orchards
Holly Johnson CSU,
Chico, College of Agriculture
Abstract
For a variety of
reasons ants are becoming a severe pest in California almond orchards,
including warmer winter temperatures in recent years, and a change in cultural
practices. Ant damage to the crop can exceed 20% in susceptible
cultivars. Many current methods of ant control are not a viable
solution for long term control. Clinch™ is a recently registered
insecticide for use in almonds with the potential to reduce ant
populations. In this study it was found that Clinch™ significantly reduced
the number of ants present in plots compared to an untreated control in a
Northern California almond orchard 163 days after treatment (p=.0783).
This study suggests that Clinch™ may be a viable method of long term ant
control.
Key words: pavement ant,
Tetramerium caespitum, southern fire ant, Solenopsis
xyloni, Clinch™, abamectin, ant bait.
Introduction
Until recently, ants were a minor almond pest in California.
However, ants are becoming a more severe pest as a consequence of changing
orchard practices. Practices such as substituting nontillage for tillage
orchard floor management, drip or micro sprinklers for flood irrigation and the
switch to IPM controls for navel orange worm control (“Hit”, 1999). Also,
growers leave nuts on the orchard floor longer for drying which leads to
increased ant damage (Reil et al., 1982). Ants damage nuts by feeding on
the kernel (Zalom et al., 1985). Ant damage can exceed 20% in susceptible
cultivars resulting in a substantial loss in profit (Darby, 2000).
Species that cause most of the damage are the pavement ant
(Tetrameriumcaespitum)and the southern fire ant
(Solenopsis xyloni). The fire ant has the widest distribution and causes
the most problems in orchards (Reil et al., 1982). Chemical spray applications
such as Lorsban have been shown to give only temporary control. These chemicals
can kill nontarget insects including beneficials and mites (Reil et al., 1982).
Abamectin, the active ingredient in Clinch™ is a stomach insecticide that kills
ant slowly after it is ingested and it also interrupts the reproductive cycle,
leaving the queen unable to lay viable eggs (“Hit,” 1999). Fire ants do
not rapidly recolonize abamectin treated soils, so Clinch™ insecticide may
eradicate the fire ants and may also delay, or prevent their reinfestation
(Campbell, 1989).
The objectives of this experiment are to determine if Clinch™ is a
viable method of long term ant control, and determine the effects of Clinch™ on
beneficial and economically harmful ants.
Materials and Method
A nine-year-old 29-acre, drip irrigated almond orchard, planted on a 20’
x 18’ spacing with a mixed clover cover crop located in Arbuckle was selected
for the experiment. Samples taken September 26th identified the types
of ants present. Samples also showed that ant distribution was fairly
uniform throughout the orchard. A buffer of four trees to prevent ants from
other plots eating the bait separated each plot. There were sixteen plots
of 8 trees by 8 trees (26,010 square feet). Plots were randomly assigned to as
an untreated control, or treatment of Clinch™ at the recommended rate of 1 lb.
per acre.
Ants were sampled two weeks prior to treatment, and after the ants
became active in the spring 163 days post treatment. All plots had five vials
with hot dogs in them for bait. Hot dogs will attract both beneficial and
economically harmful ants, providing an estimate of the number of ants
present. Hot dog vials were placed in the plots for one hour, then capped,
and frozen. The ants in the vials were then counted, species identified,
and the total ants and total harmful ants were analyzed. Data was analyzed using
Analysis of Covariance, with initial sample counts used as the covariant and a
.08 level of significance.
Results
Treatments were shown to have a significant effect for total harmful
ants (p-value of .0752). See Table 1 for ant counts. Treatments also
significantly reduced the number of total ants (p-value of .0783). See
Table 2 for counts.
Table 1. Counts of harmful ants before and after treatment.
Control
Treatment
Before Treatment
895
1306
After Treatment
876
55
Table 2. Total ants before and after treatment.
Control
Treatment
Before Treatment
901
1351
After Treatment
886
70
Discussion
This study resulted in a significant
reduction in ant populations with the use of Clinch™. Results indicate
that Clinch™ significantly reduced ant populations in the plots at over a period
of 163 days. Therefore, this study could suggest that Clinch™ might be a
viable method of inexpensive long-term ant control. Although Clinch™ had the
same effect on both beneficial and harmful ants, it is advisable to use it if
there is a significant number of harmful ants in the area to be treated because
of the potential loss of income.
By
using estimated 1999-2000 crop yields of 1,730 lbs./acre and a projected price
of $1.36/lb (Adu-Asamoah, 1999) the projected savings resulting from the use of
Clinch™ follows. Clinch costs $11.80/acre, and has minor application
costs. At a 10% reduction in ant damage $223.45/acre could be saved.
At only a 1-% reduction in ant damage $11.55/acre could still be saved. This
study suggests that Clinch™ is an inexpensive method of long term (month’s) ant
control that offers great benefits.
Future studies should be conducted to determine how immediately a reduction in
ant activity occurs, what application intervals are necessary for longer term
control, if there is a corresponding reduction in damage to nuts at harvest and
how long the kill lasts.
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