European Grapevine Moth (EGVM) – First Flight 2011


Large signs are posted throughout the Napa Valley to help raise awareness in the community.

The first flight is over and numbers are looking very good in comparison with last year.  In 2011, there have been 87 moths caught in Napa County – compared to almost 100,000 caught during the first flight in 2010.  However, there are also over 10,000 acres currently under mating disruption (MD), which will skew the findings.  When mating disruption is used, male moths are not only be hindered from finding a mate, but also have difficulty finding traps, which disperse the same sex pheromone to attract males to the females.  However, even with the wide usage of MD, 87 individual moths is a monumental improvement.


Signs of EGVM – What to Look For

Bloom is an effective time to scout for EGVM feeding damage.  As larvae feed on flower clusters they form a web that creates clumps of flower caps, flower particles (stigma, anthers) and frass (excrement).  These clumps often turn brown and discolored as larva feed on the tissue.  At this point, damage is easier to identify than after bunch closure and into maturation.  Look for discolored clumping in flower clusters as well as white webbing.

Larvae create a webbing in the flower cluster while feeding.

Stuck caps and webbing form a sticky mass that can be more easily identified during bloom. Larvae will feed on all phases of berry development and eventually enter a berry.


Second Flight – What to Expect

The second flight will start in mid to late June when the larvae that are currently feeding on flower clusters emerge as moths, mate, and lay eggs on the green berries.  Cooler temperatures will delay the second flight and spread out the emergence of adult moths.  This makes it more difficult to time a single spray for total coverage.  A warmer June would help condense the lifecycle and give growers a concentrated window to target spray programs.


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