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Far Left: First generation larva feeding in
pre-bloom flower cluster.
Left: Second generation larva feeding
inside a post-veraison berry. Note webbing
and feeding holes in berry.
the most effective
and least disruptive insecticide
application at the best timing.
In particular, we need to avoid exacerbating
natural enemies of grape
mealybug. This could create a more
severe problem, such as the increased
spread of viruses causing grapevine
leafroll disease. Finally, the highest
risk pathways in which these insects
spread were investigated, to help regulatory
agencies develop effective containment
programs.
What was learned about EGVM in
Napa County vineyards in 2010?
European grapevine moth (EGVM) completes
three generations per year in the
majority of the grape growing regions of
California. Models predict the possibility
of a partial fourth generation
in the Central San Joaquin Valley,
although populations in that region
are too low to be able to verify this
in the field.
Eggs are laid by females on or
near flowers or fruit. Larvae develop
through five stages before pupating.
Adults emerge from pupae. One generation
is defined as the development
from egg to adult. The spring
(first) generation develops from bud
break through berry set. The summer
(second) generation develops from
berry set through post-veraison. The
late summer/fall (third) generation
develops from post-veraison through
post-harvest.
This insect spends the winter as
pupae under the bark, in a resting
state of reduced metabolism (diapause)
to survive cold temperatures.
We are currently verifying a degreeday
model that will be useful in predicting
the occurrence of events in the
EGVM life cycle.
The main host of consequence identified so
far in California is grape (Vitis vinifera). Moth
larvae feed preferentially on grape
flowers and fruit. Untreated populations
can cause extensive damage to
clusters, mainly as a result of secondary
fungal infections.
Olive flowers were a minor host in
Napa County during the first generation
of 2010. The number of eggs and
larvae found on olive flowers was 0.3
to 3.0% of what was found in vineyards
during regular sampling. Olive
fruit did not host either the second or
third generations.
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Monica L. Cooper,
Lucia G. Varela, Rhonda J. Smith,
University of California Cooperative Extension
nvasive species are an increasing
threat to agricultural sustainability
in our global economy. Detection
of an invasive species triggers the
development of regulatory programs,
and a need for research and educational
programs.
Regulatory programs encompass
pest detection and containment efforts
such as trapping, quarantines, and
treatment recommendations. Such
programs are coordinated locally by
Agricultural Commissioners, statewide
by the California Department of Food
and Agriculture (CDFA), and nationally
and internationally by the U.S.
Department of Agriculture (USDA).
The regulatory program for the
European grapevine moth (EGVM),
Lobesia botrana, was developed in
response to the pest’s first detection
in North America, in Napa County in
September 2009.
A 2010 detection program deployed
pheromone-baited delta traps in all
vineyard regions of California, at densities
of 16 to 25 traps per square
mile. Male moths were found in traps
in 10 California counties: Fresno,
Mendocino, Merced, Monterey, Napa,
San Joaquin, Santa Clara, Santa Cruz,
Solano, and Sonoma.
To date, populations of this insect
have not been found in North America
outside California. Napa County populations
were the largest: more than
100,000 males were trapped, compared
with 128 males in all other counties
combined (Table I).
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During an aggressive treatment
program, populations in Napa
County decreased from 99,236 moths
caught during the first flight to 1,278
and 279 in the second and third
flights respectively.
A quarantine program is established
if two or more moths or any
other life stage is detected in a generation.
Of the 10 counties, only
eight counties have areas under
quarantine. Single moth detections
in Monterey and Santa Cruz counties
did not trigger quarantines.
In four counties, very few moths
were trapped and treatments were
applied in 2010. If no moth is caught
in these areas during the 2011 growing
season — at a density of 100 traps
per square mile and without mating
disruption — these areas may qualify
to be removed from quarantine. In
the remaining counties, quarantine
restrictions will remain in 2011.
Research and educational programs
are addressing the need for reliable scientific
information on pest identification,
biology, and management. Researchers
evaluate the effectiveness of tools such
as traps, lures, and pesticides.
When EGVM was detected, growers,
researchers, and regulatory agencies
were confronted with many unknowns,
including a lack of experience with the
life cycle under California conditions,
and the role that alternate hosts have
on development and mechanisms
of pest spread. There was a need to
develop pest management strategies
aimed at eradication.
This is very unlike the situation in
Europe, where the objective is to obtain
clean fruit at harvest, not to completely
reduce populations. Studies
were needed to identify
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