In an effort to help growers and crop scouts identify this insect, a description and photographs are provided here. Grape mealybug overwinters under loose bark or in crevices. As temperatures increase in the spring, the yellow-brown 'crawler' stage moves to the clusters and developing foliage to feed. The insect grows through a sedentary nymph stage and then becomes an adult. This mid-summer generation reproduces, creating a second generation that reaches maturity late in the season.
Vines can tolerate the removal of sap by mealybugs, but their excrement is the main cause of damage.
The blackening of grapes shown in the photograph below is caused by sooty mold fungus that develops on the honeydew secretion. Mealybugs are naturally kept under control by lacewings, ladybirds, pirate bugs, and spiders. Maintaining a pest management program that does not destroy your bio-control agents is the easiest way to avoid mealybug problems. Chemical control works best when sprays are aimed at the mobile crawler stage. When mealybugs are in the egg sac, or settle and are covered with wax, it is harder for insecticides to reach them.