Vine Mealybug


Agricultural Commissioner Sealer of Weights and Measures

Greg Clark, Agricultural Commissioner Sealer of Weights and Measures

Vine Mealybug

 Beginning in 2012, The Ag Commissioner's Office conducted an enhanced vine mealybug trapping program of 25 traps per square mile, well above the previous regimen of seven traps per square mile.  By analyzing the number of males found in each of the traps, staff is able to detect new areas of infestation as well as track reductions in population.  


Maps of 2013 Vine Mealybug finds in Napa County now available:

Full-County Overview



Soda Canyon


South Napa

Deer Park

St Helena

Mid Valley

Wooden Valley

North Napa


Please note: Trapping was not conducted in Carneros in 2013 because the area is considered to be widely infested as evidenced by the 2012 trap data.

Historical data also available online. View 2012 Maps


Related Information: 

Napa County Vine Mealybug Program Components 

Napa County UCCE Vine Mealybug Page

Winery Vine Mealybug Guidelines

Argentine ant management: Liquid bait program for vineyards  


Vine Mealybug Description and Biology

Vine mealybug adult male, Photo by Jack Kelly Clark, UC Statewide IPM Project, Regents, University of California


Mealybugs are soft, oval-bodied insects that are pink in color with a white waxy covering that extends into filaments along the margins of their bodies. Adult females lay their eggs in a white, cottony ovisac. Eggs hatch into small nymphs that are called crawlers. These young nymphs are highly mobile and may move or be carried by birds, wind, or ants to other vines. Nymphs gradually increase in size to become adult females or males. Females are the typically observed form of the mealybug, and adult males look quite different. They look like tiny wasps and are active fliers that locate the adult females by pheromone attraction. Several biological factors combine to make Vine Mealybug (VMB) a pest of great concern: 


  • Vine mealybug adult female, Photo by Jack Kelly Clark, UC Statewide IPM Project, Regents, University of CaliforniaVMB can be found feeding on all parts of the vine, including the root system, throughout the year. This is not true of the other mealybug pests of grapes, which are mainly found on the above-ground portions of the vines. All stages of VMB may overwinter underneath the bark of the trunk or below the soil line on the root system. Its underground habit provides protection from parasitoids and contact insecticides. VMB are also protected by ants, which “tend” the mealybugs for honeydew and fend off natural enemies.
  • VMB has a number of biological attributes that result in rapid increases in population. The females can deposit more than 500 eggs (average is about 300 eggs per female) and there are 4-7 generations per year, a factor leading to overlapping generations. Typically, pest control applications are timed to attack the insect when it is at its most vulnerable life stage, and this is a challenge with VMB, since at any one time, all life stages may be present.
  • VMB excretes large amounts of “honeydew” that results in sooty mold growth and eventual defoliation.
  • Finally, VMB can vector viral diseases of grapevines, such as leaf roll virus.

In the words of Mark Battany, UCCE Viticulture Farm Advisor in San Luis Obispo County: “The vine mealybug has the potential to become our most damaging and expensive insect pest in California vineyards.”




Why Vine Mealybug is Such a Serious Threat


Ongoing Pest Management Programs Necessary

This is a special challenge in this era of reduced input and sustainable farming and requires vineyard managers to be informed, diligent, and persistent to produce high-quality fruit that is not fouled by honeydew, mold, or insects.

Growth and Vigor Reduction

VMB feeds on the plant sap of the vines and reproduces rapidly to develop high populations — the result being the reduction of vine vigor, fruit set, and growth.

Fouling of Fruit

VMB excretes large amounts of honeydew as it feeds, providing a substrate for the growth of sooty mold and reducing the quality of the harvested grapes, to the extent that fruit from untreated vines is unmarketable.

History of the Vine Mealybug in California

The vine mealybug, Planococcus ficus, is an exotic pest first found in California in the Coachella Valley, Riverside County in 1994. In 1998, it was detected in Kern County and Fresno County, where it was probably introduced on contaminated vineyard equipment from the Coachella Valley. For the next few years, it is believed that grapevine nurseries in the southern San Joaquin Valley shipped infested vines throughout the state before they realized the seriousness of the pest. Currently most, if not all, California grape-producing counties have infestations, including Alameda, Amador, El Dorado, Fresno, Kern, Lake, Merced, Monterey, Napa, Riverside, Sacramento, San Joaquin, San Luis Obispo, Santa Barbara, Santa Clara, Solano, Sonoma, and Tulare, and Yolo.

The threat posed by the Vine Mealybug to our vineyard and winery industry is a serious one. The insect should not be allowed to become widespread in Napa County. Low populations are less likely to spread so it is imperative to take positive steps to manage VMB . Widespread infestation means increased pest management costs in our vineyards into the indefinite future. Besides adding significantly to production costs, increases in pesticide use would be an affront to sustainability programs, and result in negative consumer reactions.