The long first generation is particularly nettlesome for organic growers. They are relegated to basically using slow acting Bt insecticides, primarily Dipel.

Dipel is effective, said Varela, but timing is critical and it may take repeated applications. She said one organic grower in the Napa infestation zone treated first-generation EGVM four times with Dipel. She recommended organic growers examine flowers very closely, opening them up to detect any first-generation larvae.

She also recommends trapping extensively to time sprays, monitoring them weekly from bud break to harvest.

“Put out as many traps as you can monitor,” she recommends.

There is also a vine-tie pheromone product to be used as mating disruption with low populations.

EGVM larvae can be confused with leafroller larvae when the worms are young. However, black or dark brown thoracic legs are the telltale sign of EGVM. The segment behind the head is darker than leafroller. The fourth and fifth instar EGVM larvae can be dark maroon.

The EGVM has at least three full generations. There may be a partial or full fourth generation, depending on climate.

Varela said while the Napa control program has been very successful and trapping last season has indicated a low population elsewhere; she said no one should let down their guard next season.

“We must continue to be very, very vigilant in 2011,” she warned. After her presentation, she said that she expects more moths to be trapped next season, even in areas where trap counts were very low in 2010.

However, she does not expect a repeat of the infestation like that experienced in Napa in 2010.

“I believe we caught it earlier than Chile, since all grape growing areas of Chile are infested.”

hcline@farmpress.com