PCC MarchApril Final Draft

Enhancing Diamondback
Moth Management
with Mating Disruption
By SURENDRA K. DARA | UCCE Entomology and Biologicals Advisor
Brussels sprouts field in Santa Maria (photo by S.K. Dara.)
Brassica crops such as broccoli,
brussels sprouts, cabbage, canola,
cauliflower, collards, kale, kohlrabi,
turnip and mustards are important
vegetable or oilseed crops. The value
of brassica vegetables, also known as
cole crops, is more than $1.2 billion in
California, which is the leading producer
of these crops. Among various arthropod
pests that attack brassica crops, the
diamondback moth (DBM), Plutella
xylostella (Lepidoptera: Plutellidae), is of
significant importance. Thought to be of
European origin, now with worldwide
distribution, DBM exclusively feeds on
cultivated and weedy crucifers. DBM
can have up to 12 generations per year,
especially under warmer climate.
Female moths deposit 150 eggs on average.
Four larval instars feed on foliage
and growing parts of young plants or
bore into heads or flower buds, resulting
in skeletonization of leaves, stunting
of the plants or failure of head formation
in some hosts. Pupation occurs
on the lower surface of leaves or in
florets. Adult moths are grayish-brown,
and when at rest, a light-colored diamond-shaped
pattern can be seen on the
upper side of the wings.
Farmers typically rely on synthetic and
biological insecticidal applications for
controlling DBM. Multiple species of
parasitoids and predatory arthropods
also provide some control. Due to a
heavy reliance on insecticidal control,
DBM resistance to several insecticides
is a common problem. Resistance of
DBM to Bacillus thuringiensis (Ferré et
al., 1991), abamectin (Pu et al., 2009),
emamectin benzoate, indoxacarb and
spinosad (Zhao et al., 2006), pyrethroids
and other insecticides (Leibee and
Savage, 1992; Endersby et al., 2011) have
been reported from around the world.
Excessive use of any kind of pesticide
leads to resistance problems (Dara,
2020) to an individual pesticide or multiple
pesticides.
Integrated pest management (IPM)
strategy encourages the use of various
control options for maintaining pest
control efficacy and reducing the risk of
resistance development (Dara, 2019).
Regularly monitoring pest populations
to make treatment decisions, rotating
pesticides with different modes of
action, exploring the potential of biocontrol
agents, and other non-chemical
control approaches such as mating
disruption with pheromones are some
of the IPM strategies for controlling
the DBM. While sex pheromones are
effectively used to manage several
lepidopteran pests and are proven to be
a critical IPM tool, mating disruption is
not fully explored for controlling DBM.
A study was conducted in Brussels
sprouts to evaluate the efficacy of a
sprayable pheromone against the DBM
and to enhance current IPM strategies.
Methodology
The study was conducted on a 10-acre
Brussels sprouts field in Santa Maria.
Cultivar Marte was planted in early
July for harvesting in December 2020. A
typical diamondback control program
includes monitoring DBM populations
with the help of sticky traps and lures
and applying various combinations of
biological and synthetic pesticides at
regular intervals. This study evaluated
the efficacy of adding CheckMate
DBM-F to the grower standard practice
of monitoring the DBM populations
with traps and lures and applying
pesticides. Treatments included 1.)
grower standard pesticide program
(See Table 1) grower standard pesticide
program with two applications of 3.1 fl
oz of CheckMate DBM-F on August 9
and September 11. Treatment materials
were applied by a tractor-mounted
sprayer using a 100 gpa spray volume
and necessary buffering agents and
surfactants. Each treatment was five
acres and divided into four quadrants
representing four replications.
In the middle of each quadrant, one
Suterra Wing Trap was set up with a
30 Progressive Crop Consultant March / April 2021