Information for Mealybugs on Grapevines

Mealybugs are tiny insects taxonomically placed in the Order Hemiptera; they are related to aphids and scale insects and are an important group worldwide for the damage they can do to agriculture crops.

Mealybugs feed on plant phloem from many parts, often producing copious amounts of honeydew, which is often the first noticed sign of a mealybug presence.
Ant species will often protect and ranch the mealybugs so they may feed on the honeydew produced.
Some species have the ability to transmit plant disease, such as leafroll virus.
Mealybugs generally have flattened, elongated oval bodies that are covered by a powdery white wax. Species can be distinguished by the presence and length of body and anal filaments.

Of important note to the foothills is Gill's mealybug (Ferrisia gilli ). As an adult, Gill's mealybug is relatively large (2-5 mm) with a lot of fine waxy filaments, making it fairly easy to identify with a hand lens. Gill's mealybug bears live crawlers, while Grape mealybug oviposits eggs under the bark of the trunk. Some key findings from previous extension agents include:

Gill's mealybugs complete 2 generations a year in the foothills
Early season they are found underneath bark
Treatment was generally timed for crawler stage around late june to july
Insecticides buprofezin (Applaud), spirotetramat (Movento), and acetamiprid (Assail) appeared effective for the crawler stage
Parasitism appears to occur readily when insecticides are not used.

Below are links to more information on individual mealybug species:

Grape mealybug UC IPM guidelines
Gill's mealybug UC IPM guidelines
Vine mealybug UC IPM guidelines

Helpful resource

Sampling program for grape mealybugs improves pest management. California Agriculture, May-June 2001.
Information on grape mealybug monitoring study with information on distribution of mealybugs on the vine at different times of the year, affecting management decisions.