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IPM 25th2005 Annual Report

UC Statewide IPM Program
HIGHLIGHTS


UC IPM Makes It Happen

UC helps vineyard crews to identify invasive pest

Mealybug identification
Photo by Stephanie Klunk
Knowing how to spot vine mealybug is vital for Diego Smart, because using insecticides in the organic vineyard where he works is not an option. Smart, a foreman at Enterprise Vineyards in Sonoma, and supervisors from several other vineyards attended a workshop to train them to recognize the key signs of vine mealybug.

Vine mealybug infestations were first found in North Coast vineyards in 2002. The pest spread from initial infestations in southern California and is now present in 16 counties. The culprit contaminates bunches and can also transmit viral diseases.

With funding from UC IPM, Lucia Varela, IPM advisor for the North Coast, conducted five educational sessions in Spanish at Sand Hill-Durell Vineyards in Sonoma in June.

"If vineyard employees know the signs, they can find an infestation early when its population is low and be able to stop the spread," says Lucia. She shows workers a slide presentation outlining the different stages of vine mealybug infestation, how to monitor it with traps, what signs to look for seasonally, and sanitation measures to reduce the spread of the pest. Afterward, participants have a chance to examine the insect under a microscope.

"Lucia's presentations are really clear and straightforward," says Smart. "She's not giving a lesson to a professor but to those who work in the vineyard. The pictures and the chance to see it under the microscope make it interesting and informative."

Lucia conducts training in May through July when workers are most likely to see vine mealybug. As temperatures warm in spring, pest populations increase and become more visible as they move from under the bark on the trunk and cordons of the vine to the canopy. By late spring and summer, vine mealybugs are found on most parts of the vine. The pest produces honeydew that drops onto the bunches and other vine parts and produces a black, sooty mold.

"Infested leaves fall to the ground prematurely in late summer, which can spread the infestation throughout and to adjacent vineyards," says Lucia. "Honeydew can cause these leaves to stick to vineyard machinery and harvest equipment, which also moves the pest to new areas. The most effective time to control vine mealybug is immediately after harvest because a larger proportion of the population is exposed. However, it's important to obtain clean fruit and to avoid spreading the insect due to premature leaf drop and at harvest. So, early detection and control is crucial."

Starting in June, many growers in the North Coast region place pheromone traps in their vineyards to see if the male vine mealybug is present. The lure placed inside each trap contains the sex pheromone that female vine mealybugs give off to attract winged adult males. If males are caught in a trap, the infestation that was the source of those males has to be located, and well-trained workers can help find them.

Currently, vine mealybug can be controlled only with insecticides, so if this insect becomes widespread, insecticide use could increase.

In 2002, a team of University of California Cooperative Extension IPM and county-based advisors developed new methods to detect and manage the pest in grape nurseries. They modified a hot-water treatment of dormant nursery stock, and it became an effective and nontoxic control method used to kill 99 percent of the mealybugs present on the stock. Commercial nurseries now treat their planting stock by immersing it for 5 minutes into three water tanks—a warming tank, a treatment tank of water above 125 degrees F, and then a cooling tank. In less than a year, this UC IPM research effort produced a safe and effective management method that was adopted by several nurseries.

UC IPM staff takes this information to workers out in the field and trains them in management practices that can reduce the movement of vine mealybug in vineyards that are already infested. Lucia has given her presentations during the last three years and trains about 400 workers annually. "We target the presentations to crew leaders since they are the vineyard's permanent employees," she says. "We empower them to take the information we've given them, along with some handouts, to go back and train their crews. Our goal is to identify infestations of vine mealybug early to limit its spread."
Lucia noted during her session that one participant asked whether the damaging effects of vine mealybug are the same in young and older plants. "Older plants have the ability to create larger colonies," she says. "One worker commented that older vines have thicker bark so vine mealybug has more places to hide. That let me know that this group quickly understood what I was explaining to them."

Workshops were held in seven locations on 10 dates in May through July, with one to three training sessions on each date.

Other instructors are UCCE Sonoma County Viticulture Advisor Rhonda Smith; Napa County Viticulture Advisor and County Director Ed Weber; and Lake County Director Rachel Elkins.

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