The vine mealybug (VMB) is a relatively new species in California, but it has spread rapidly and it's coming our way. It has been found in vineyards in Monterey and Santa Clara Counties. The VMB has the potential to become one of our most important vineyard pests. This was the warning from Larry Bettiga, U.C. Farm Advisor during our November Integrated Pest Management workshop at Cooper-Garrod.        

Except for its lack of a tail, the VMB is difficult to distinguish from other, more common mealybugs. The VMB, however, is more difficult to control and causes greater damage. They can infest an entire vine, feeding on the grapes and under the bark, where sprays don't reach. They feed out further on the canopy than other mealybugs and produce more 'dew', which attracts black soot. They can invade the soil.  Prolonged infestation can weaken vines, reduce vine growth, yields and quality of fruit, and increases the spread of viral diseases.  Effective treatment for VMB requires expensive, prolonged chemical application that can disrupt sustainable integrated pest management programs.

VMB is spread by infested plants, birds, farm equipment, fruit, leaves, vineyard workers. But primarily it's been spread by nursery stock. Ask your nursery what treatments (i.e. heat) they've done to prevent the spread of VMB. 

The key to eradication is to identify the pest ASAP and treat promptly.  Pheromone traps (one per 20 acres, available from Western Farm Service) are an essential identification tool, and should be in place by the end of March.  They should be examined at least every two weeks.  It is recommended that you trap if you've planted stock since 1998, or if your vineyard is adjacent to an infected site or has been visited by personnel from an infested site. Train your harvest and pruning crews to recognize the pest. Identification posters are available from Larry Bettiga's office.

The Santa Cruz County Agricultural Commissioner's Office has mealybug traps and lures available. You can stop by the office and pick them up, then return them for analysis. The lab will let you know whether any mealybugs have been identified from your traps. If they come back positive then proceed with treatment options. If negative, keep trapping and focus on biodiversity in the vineyard.

Treatment is easier on younger vines - the bark is thinner and the root system less complex so there are fewer places for the pest to hide. The presence of ants, which 'farm' mealybugs, on your vines is an indicator of infestation. Ants protect the VMBs from parasitic wasps, so it might help to get rid of the ants. If VMB is first discovered in late summer or fall, apply a postharvest treatment of a foliar insecticide to kill mealybugs on the leaves and wood so that the infestation is not spread to other parts of the vineyard when leaves drop or when the vines are pruned. Postharvest treatments are only recommended the first season that vine mealybug is discovered.  

Starting the year, apply a (pre-budbreak) delayed dormant treatment of chlorpyrifos (Lorsban®) or buprofezin (Applaud®) and then treat with imidacloprid (Admire®) at bloom. Make either a single application of imidacloprid (Admire®) or a split one, depending on soil type. During summer, treat with buprofezin (Applaud®) if insects are active. Other materials (methomyl and dimethoate) are available for treating vine mealybug during summer, but they are not as effective and are more disruptive of beneficials.

More details on vine mealybugs, including details on trapping, can be found at the following websites: 
http://cemonterey.ucdavis.edu/viticulture/vine_mealybug.htm
http://vinemealybug.uckac.edu/
http://ipm.ucdavis.edu/

(IPM Workshop, 18 November 2004)