How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Vine mealybugs are small (adult females are about 1/8 inch in length), soft, oval, flat, distinctly segmented, and covered with a white, mealy wax that extends into spines (filaments along the body margin and the posterior end). The vine mealybug has a pinkish body that is visible through the powdery wax, and it is slightly smaller than the Pseudococcus mealybugs. The waxy filaments that protrude from the body of the vine mealybug are shorter than those on the Pseudococcus mealybugs, and the vine mealybug does not possess long tail filaments. The adult male is smaller than the female, has wings, and flies short distances to mate. There are three to seven generations a year.

All or most life stages of the vine mealybug can be present year-round on a vine depending on the grape-growing region. In the North Coast during winter months, the only life stages found are nymphs located under the bark predominately at the graft union, on trunk pruning wounds, and below the base of spurs. In other regions during the winter months, vine mealybug eggs, crawlers, nymphs, and adults are under the bark, within developing buds, and on roots.

As temperatures warm in spring, vine mealybug populations increase and become more visible as they move from the roots and trunk to the cordons and canopy. By late spring and summer, vine mealybugs are found on all parts of the vine: hidden under bark and exposed on trunks, cordons, first- and second-year canes, leaves, clusters, and roots. Ants may transport vine mealybug from the roots to above ground plant parts where they continue to tend vine mealybugs throughout the remainder of the growing season.

In the North Coast, vine mealybug has not been found on vine roots; however, in other regions, it has occasionally been found on the root system, especially in areas with light soils. Other mealybugs found infesting grapes are only found on the aboveground portions of the vine. In addition, the vine mealybug is much more likely to be found on leaves during the growing season than the other mealybugs. During summer when vine mealybugs are in the canopy, they can be located well above the fruit zone and will lay eggs on the leaves, while Pseudococcus mealybugs do not. Vine mealybug does not diapause during the winter, and it appears to be more sensitive to cold temperatures than grape mealybug.

DAMAGE

Damage by the vine mealybug is similar to that of other grape-infesting mealybugs in that it produces honeydew that drops onto the bunches and other vine parts and serves as a substrate for black sooty mold. If ants are not present, a vine with a large population of this pest can have so much honeydew that it resembles candle wax. Also, the mealybug itself will be found infesting bunches making them unfit for consumption. Like the grape, obscure, and longtailed mealybugs, vine mealybug can transmit grape viruses.

MANAGEMENT

In California, the vine mealybug occurs in the Coachella and Central valleys, the Central and North coasts, and the Sierra foothills. The host range of the vine mealybug includes grape, fig, date palm, apple, avocado, citrus, and a few ornamentals. To date, vine mealybug has only been found feeding on grapevines in California. This pest is spreading to new areas of the state and IPM programs are under development.

Because several different species of mealybugs may infest grapevines, it is important to know which species of mealybug is present because management programs for the various mealybugs differ. If you find mealybugs in your vineyard, collect the largest mealybugs you can find and place them in a jar of alcohol or sealed plastic bag. Take the sample to either your UCCE Farm Advisor or county agricultural commissioner. The phone number and location of these offices can be found in the government pages of the phone book under "County Government." For more information on identification, visit UC Kearney Agricultural Center's mealybug web page.

Biological Control
The parasites that attack Pseudococcus mealybugs do not attack the vine mealybug, therefore two potential candidates for natural control have been imported and released in Riverside, Kern and Fresno counties. The most successful of these has been Anagyrus pseudococci. This species has provided up to 20% parasitism in some vineyards in the Coachella Valley, and up to 90% parasitism in the San Joaquin Valley. It is extremely important to promote parasites because they are active late in the growing season and can reduce vine mealybug populations before the pest begins to move to the lower part of the trunk in October. To a limited extent, they can parasitize vine mealybug when it is located under the bark where chemicals cannot penetrate. Ants must be controlled to keep them from interfering with these natural enemies (see the section on ANTS for information on their control).

In the coastal regions a lady beetle called the mealybug destroyer, Cryptolaemus montrouzieri, attacks vine mealybug eggs and crawlers.

Cultural Control
The female mealybug is unable to fly so it must be carried by humans, equipment, birds, or be present on vines at the time of planting. Do not allow contaminated equipment, vines, grapes, or winery waste near uninfested vineyards. Movement of equipment that pushes brush or any over-the-row equipment can be a major source of infestations in new locations; steam sanitize equipment before moving to uninfested portions of the vineyard. Do not spread infested cluster stems or pomace in the vineyard. To reduce contamination, cover all pomace piles with clear plastic for several weeks, and avoid creating piles that consist predominately of stems.

Organically Acceptable Methods
Biological and cultural controls are organically acceptable management tools. No research studies have yet been done in California on the efficacy of oils or calcium polysulfide in controlling vine mealybug, but they have not proven effective in controlling the grape mealybug.

Monitoring and Treatment Decisions
Follow the monitoring guidelines in DELAYED-DORMANT AND BUD BREAK MONITORING to monitor these and other pests in the early season and record results on a monitoring form (100KB, PDF). View photos to identify among various mealybug species.

Pheromone traps for this pest are available and useful for determining if a vine mealybug infestation is near or in your vineyard. The lure that is placed inside each trap contains the sex pheromone that female vine mealybugs use to attract winged adult males. Tent-shaped, red traps are recommended because the shape and color tend to reduce the number of non-target insects that are caught.

Place traps in vineyard by April 1 in the southern San Joaquin Valley to May in areas further north and June in the North and Central Coasts:

• Choose two trap sites for each 20-40 planted acres.
• Put one trap in the center of the block and the other on the edge near a staging area. These traps can attract vine mealybug males from as far away as 1/4 mile.
• Attach traps to the trellis wires so that they are in the cluster area.
• Label the trap with the block name and row number of its location and the dates it remains in the vineyard.
• Check traps for the presence of male vine mealybug every 2 weeks through November.
• Follow the manufacturer's recommendations for storing and replacing pheromone lures.
• Record observations on a monitoring form.

It is essential to use a dissecting microscope to identify the male mealybug. (Male vine mealybugs are smaller than adult thrips and are very difficult to see even with a hand lens.) The sex pheromone is specific to the vine mealybug, but the traps may also contain other male mealybugs depending on the site. If there are questions as to the identification of the mealybug species, take samples to a farm advisor or county agricultural commissioner or refer to the Male Vine Mealybug Identification Sheet (100KB, PDF).

The number of males found in a trap depends upon its proximity to the infestation and to the time of year. In the North Coast, new infestations have been located near traps that caught very low numbers in June (5 to 10 males per trap per week) and high numbers in fall (more than 50 males per trap per week). In the San Joaquin Valley, an infested vineyard will have between 20 to 300 or more males per trap per week. In either region, low numbers of male vine mealybugs found in a trap may mean that the infestation is located in an adjacent block or in a more distant vineyard. If males are found, increase the number of traps in the vineyard, and locate the infestation by examining lower leaves for honeydew. After bloom, pull basal leaves to look for vine mealybug crawlers and honeydew in the canopy and look under the bark on the trunk and cordons. During bloom and veraison, treatment may be warranted for a high population of nymphs on leaves, but if possible it is better to wait until postharvest to treat in order to preserve natural enemies.

Vine mealybug produces more honeydew than other mealybugs, and this is particularly noticeable if there are no ants present. Thus, when searching for vine mealybugs during summer, look for honeydew exudates on the clusters, trunk, and cordons. These exudates will resemble melted candle wax, if the infestation is severe, and basal leaves will appear shiny and sticky. Sooty mold will grow on the honeydew, and permanent parts of the vine will appear black in fall and winter. Also look for fallen leaves beneath the canopy in July and August. To locate less severe infestations, it is necessary to look for all stages of the insect under the bark predominately at the graft union, on trunk pruning wounds, and below the base of the spur. Also, the presence of ants moving up and down the vine may indicate the presence of Pseudococcus mealybugs, vine mealybug, or European fruit lecanium scale.

If vine mealybug is found in the vineyard, treatment is recommended. There are two approaches to managing mealybugs: eradication and yearly management. Eradication using chemical applications is most likely to be successful in young vineyards or in vineyards where only a few isolated vines are infested. In mature vineyards with heavy, loose bark, strip the bark off the trunk and cordons before a chemical application to increase chances of success. Eradication is most probable in areas where there are no nearby vine mealybug-infested vineyards. If 2 years of effort do not eliminate vine mealybug from the vineyard, then switch to a yearly management program.

Management in newly infested vineyards (eradication). If vine mealybug is discovered in the vineyard in late summer or fall, and if preharvest interval restrictions permit, apply methomyl or dimethoate to infested vines. Take precautions during harvest operations to prevent movement of insects to noninfested vines. Apply a foliar insecticide immediately after harvest if possible (before the nymphs begin to move to the lower parts of the trunk), 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.

The following year, apply a delayed dormant treatment of chlorpyrifos or buprofezin and then, in areas with light soils, treat with imidacloprid at bloom. Make either a single application of imidacloprid or a split one, depending on soil type. During summer, treat with buprofezin. 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. (In the North Coast, the first application of buprofezin is not recommended until late spring or early summer; imidacloprid is not as effective in controlling pests in heavy clay soils.) The University of California recommends following this program for a maximum of 2 years. If vine mealybug is still present in the vineyard after 2 years, switch to a yearly management program.

Yearly management program.
Areas with light-textured soils— In vineyards known to be infested with vine mealybug, make a bloom time application of imidacloprid either as a single application or a split application through the drip-line. The following year, either treat with chlorpyrifos in the delayed dormant period, or with buprofezin in the delayed dormant period and again in the summer. Alternating insecticides each year helps to prevent the development of insect resistance.

Areas with heavy clay soils— In vineyards known to be infested with vine mealybug, make an application of buprofezin or methomyl as soon as crawlers are present on the leaves (in late spring to early summer); a second application can be made no sooner than 14 days later. Apply a foliar insecticide immediately after harvest to kill mealybugs before the nymphs begin to move to the lower parts of the trunk in late October.

PDF: You need a PDF reader, such as Acrobat Reader version 5 or later, to view or print this PDF. If no reader is installed on your computer, you can download a free copy of Adobe Acrobat Reader.

PUBLICATION

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
F. G. Zalom, Entomology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
P. A. Phillips, UC IPM Program, Ventura County
D. R. Haviland, UC IPM Program, Kern County
K. M. Daane, Kearney Agricultural Research Center, Parlier
M. C. Battany, UC Cooperative Extension, San Luis Obispo County
Acknowledgment for contributions to the insects and mites section:
J. Granett, Entomology, UC Davis

Top of page