Vine Mealybug Meets its Match at Spring Mountain Vineyard

There will be a town hall meeting on vine mealybug at the Veteran's Home, Grant Hall, Yountville, California, on February 21, from 1-4:30pm. Ron Rosenbrand will sit on the grower panel at this important meeting.
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Spring Mountain Vineyard, known for its intensely flavored hillside Cabernets, may become better known as the place where a clever and environmentally friendly practice was developed to eradicate what has quickly become the number one concern for grape growers in California: vine mealybug.

One of the most destructive of all insect vineyard pests, Vine Mealybug first entered central California vineyards in 1998, and by 2003 had spread to 17 counties, including Napa and Sonoma, originating in infested nursery stock. Once in a vineyard, VMB moves from vine to vine quickly, reproduces voraciously, and is easily carried from one vineyard site to another by environmental conditions like wind, on equipment and even on worker’s clothing. It’s presence is obvious: vine mealybug leaves a sticky, sweet substance called honeydew on grapevines, rendering the clusters useless for winemaking.

For three years, Spring Mountain’s vineyard manager, Ron Rosenbrand, has been waging a tough battle against VMB. Though he was able to keep the bug isolated to one small block of the vineyard using traditional methods, he was making no progress on eradicating it. Dissatisfied and determined, he went looking for an environmentally friendly solution to the problem. He contacted researchers at the University of California at Berkeley and began working with their cutting edge research and technology. After presenting his case to the Napa County Agriculture Commission, Rosenbrand was the only grape grower to get permission to use a biological offense against the pest. For the past year, Rosenbrand and UCB have pioneered an experimental, biologically integrated program targeted at eradicating vine mealybug. They began to systematically release several species of predatory and parasitic insects into the affected portion of the vineyard.

From April to November of 2006, at two week intervals, Rosenbrand released several species of beneficial insects into the vineyard. In total, he released 570,000 Ladybugs, 350,000 Green Lacewings, 35,000 Mealybug Destroyers and 12,000 Minute Pirate bugs. All of the insects directly feed on vine mealybug in its adult or larval stage. Since one female vine mealybug can deposit up to 700 eggs at a time and produce 4 to 7 generations in a single season, interval releases kept a constant population of beneficial insects in place to combat the vine mealybug’s overlapping generations.

In addition, UC Berkeley researchers released two species of parasitic wasps, Coccidoxinoides Peregrins and Anagyrus Pseudococci into the Spring Mountain Vineyard. A total of 95,000 of the tiny Coccidoxinoides wasps measuring a mere 1/32 of an inch each, were released. Of the Anagyrus species, both male and female wasps were released. The adult wasps lay their eggs inside the bodies of the adult vine mealybug. As the new wasps hatch, they naturally feed on the mealybug.

In conjunction with the predator releases, Rosenbrand deployed UC Berkeley’s experimental pheromone cards in the vineyard. Meant to disrupt mealybug mating, the cards emit the odor of the female, thus confusing the male and making it very difficult for him to find a mate. Females can still reproduce without males, but don’t lay nearly as many eggs.

“The mating disruption only targets the male vine mealybug and is nontoxic to the other beneficial insects in the vineyard”, says Rosenbrand.

Rosenbrand’s workers have repeatedly observed ladybugs eating vine mealybugs in the affected portion of the vineyard. UCB researchers monitored Spring Mountain Vineyard throughout the growing season and found large percentages of VMB that had been parasitized by wasps. In the isolated infected block, Spring Mountain Vineyard saw a 50% reduction in the numbers of the pest during October, traditionally the most prolific month for VMB.

“I am very encouraged by the success of this bio-friendly program over the past nine months. Although the program is still experimental and the jury is still out, to be able to step away from traditional methods toward a safe, biological approach is very gratifying. It is my hope that with continued release of the UCB wasps over the winter, and by steadily increasing the breeding populations of beneficial insects, we can eradicate vine mealybug,” says Rosenbrand.