UC IPM Makes It Happen
IPM programs being developed for new mealybug plaguing pistachio growers
A
two-tailed pest is hitchhiking its way across California at breakneck
speed, feeding on pistachios, almonds, and grapes, and surviving
in a wide range of climates. But researchers believe that the insect
can
be kept in check naturally.
The new mealybug, Ferrisia gilli, was first identified in pistachios
near Tulare, California, in 1998. Since that time, it has spread
to more than 3,000 acres of pistachios statewide.
Management programs for the mealybug in pistachios during the
last few years have revolved around the use of two organophosphate
and
carbamate insecticides. "Multiple applications of these products provide
some control, but are in no way a substitute for an integrated pest management
approach," says UC IPM Advisor David Haviland. "Transitions
to an IPM approach became more of a reality in 2005 because we gained
a better understanding of the mealybug's biology and its adaptation
to certain cultural controls. A more IPM-compatible insecticide is now
available, the insect growth regulator, buprofezin. This regulator affects
the insects' hormonal balance, suppressing the development of
eggs, metamorphosis, and adult formation."
The potential for biological control of F. gilli is huge, says
David. In 2005, he found that heavy mealybug populations in
almonds can
be reduced naturally to near undetectable levels without the
use of chemical
insecticides.
Mealybug reductions were attributable to at least two species
of parasitic wasps, a predatory beetle, lacewings, and possibly
ants.
David is collaborating
with UC Berkeley biocontrol specialist Kent Daane to investigate
the role of these different biological control organisms to
see how each
can be used to control F. gilli in different cropping systems.
F. gilli belongs to a type of mealybug that is found
throughout the world, feeding on many different plants. The
pest is believed
to
have originated
in the southeastern United States. In California, in addition
to pistachios, it has been found in almonds, grapes, persimmons,
stone
fruits, and
several ornamentals, such as fruitless mulberry.
The insect has a pink body covered in white filamentous, waxy
excretions. The insect has two pink stripes running down
the length of its
body and two white tails. The mealybugs feed by sucking plant
juices, and they
produce large amounts of a sticky liquid called honeydew.
This liquid
develops into a sooty mold that can turn bark, leaves, and
nuts completely black.
During the fall, adult female mealybugs congregate on the
main scaffolds and trunks of trees and vines. This is an
easy time
of year to find
the mealybugs due to the furry appearance they give to
the bark. The females
produce large numbers of offspring that stick around during
the winter in cracks and crevices.
During the spring, the pest feeds primarily on woody parts
of the plant. As the season progresses, they move onto
fruiting structures
and hulls
in pistachios, where they can reduce nut quality and
possibly yields.
"Due to the widespread range of this pest, it's difficult
to predict where it'll go next," says David. "Even
growers who don't yet have this pest should focus on preventing
its spread. They can accomplish this by keeping work crews and equipment
that have been in infested blocks out of those that are clean. Equipment
such as harvesters, bins, mowers, and disks should be cleaned before
moving them from orchard to orchard."
David and other UC researchers presented the latest information on the
mealybug for pistachio growers, PCAs, and harvesters at a series of
meetings in Tulare County in June and August 2005. "In less than a year,
we've delivered an entire IPM package to growers and Pest Control
Advisers with information on how to find the pest, monitor it, its
effects on yield, and basic biological and control information," he says. "The
cross-commodity nature of this pest will allow us to coordinate efforts
of the pistachio industry with those of the almond, grape, stone fruit,
and other industries that want to know more about managing this insect."
Growers
who find mealybug infestations are encouraged to report them to their
local UCCE office.
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2005
Annual Report 