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University
of California Cooperative Extension
Mealybugs: Site developed
and maintained by the Kearney Agricultural Center, |
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Because different species of mealybug require different methods and timing of treatment, it is important to first identify which species is present at a particular vineyard before considering methods of control.
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Chemical
control
Mealybugs found on grapevines are difficult to control chemically because most species spend much of their lives hidden beneath bark, on roots, or on some other protected part of the vine. The timing of insecticide applications is critical in order to coincide with periods of maximum vulnerability for mealybug populations. In addition, ants tending mealybugs must be controlled to ensure maximum effectiveness from the mealybugs' natural enemies. Research is improving pest management programs. To access the most up-to-date recommendations for mealybug and ant control, call your local University of California Cooperative Extension Farm Advisor's office (listed under County Government in your phone book) on visit the University of California Statewide Integrated Pest Management Program website (http://www.ipm.ucdavis.edu). On the website, recommendations can be found under UC Pest Management Guidelines. (Return to top.) |
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Biological
Control
There are many insect parasites that attack mealybugs found in vineyards, but most are specific to only one or two mealybug species. Most life stages of the grape and longtailed mealybugs are parasitized by the tiny wasp Pseydaphycus angelicus. However, this parasite prefers second- and third-instar nymphs. Additionally, grape mealybug is parasitized by another tiny wasp, Acerophagus notativentris. Parasitism rates in the field range from 10 to 90 percent depending on the season and vineyard management practices. Studies have also shown that if parasites are present and active early in the season, substantial reductions in mealybug densities can occur. To improve biological control of the obscure mealybug, two tiny wasps, Pseudaphycus flavidulus and Leptomastix epona, were imported from Chile in the 1990s. P. flavidulus attacks second- and third-instar nymphs whereas L. epona attacks large third-instar nymphs and adult mealybugs. Only P. flavidulus has been shown to establish in California. It can help reduce densities of obscure mealybug as long as ants are controlled at the same time. Without ant control, most of the mealybug parasites mentioned here are less effective because the ants interfere with adult parasites, often attacking and killing them. Studies of biological control of the vine mealybug have revealed that a small wasp, Anagyrus pseudococci, attacks second- and third-instar nymps and adult mealybugs. This parasite was introduced throughout California in the 1940s to control the citrus mealybug. Additional studies coordinated by D. Gonzalez at the University of California, Riverside, were conducted, and new strains of A. pseydococci and another wasp, Leptomastidea abnormis, were introduced into the Coachella Valley in the late 1990s. L. abnormis, which prefers to attack first- through third-instar mealybug nymphs, has also been introduced into the San Joaquin Valley over the past few years. These parasites are beginning to establish permanent populations in these regions. To determine if parasites are active against mealybugs in a vineyard, it is easiest to look for mealybug mummies. The mummies are the dead hulls of mealybugs that remain after the parasites have fed and developed inside. Mummies are typically round or oval in shape and appear to be somewhat bloated. Also, the shell of the mummy is hard, and the white wax is often faded or gone. Occasionally, there are holes in the mummy where adult parasites have emerged. To distinguish between a mummy and a large mealybug, gently prod it. A live mealybug will move, and a mummy will not. Arthropod predators also attack mealybugs in vineyards. The most common arthropod predators in the vineyard are spiders; however, their effectiveness against mealybugs is not well known. Insect predators include the mealybug destroyer (Cryptolaemus montrouzieri), brown lacewing larvae (Hemerobius spp.), and minute pirate bugs (Orius spp.). Larvae of the mealybug destroyer look very much like mealybugs themselves. However, they are actually a species of lady beetle. The adult beetle is black with a light brown head and is slightly larger than the head of a pin. |
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Cultural
Control
Control of mealybugs in vineyards can be enhanced by the incorporation of various cultural practices. Proper sanitation practices are very important in managing the spread of vine and pink hibiscus mealybugs. This is because all life stages of these mealybugs can be transported on farm equipment, trellis materials, harvesting supplies, plant parts (clusters, leaves, small pieces of cane, and so on), and clothing of fieldworkers. To reduce the spread of these mealybugs, farm equipment and harvesting supplies should be cleaned of all plant parts prior to movement to an uninfested area. In addition, workers should not move from an infested to an uninfested vineyard on the same day. Using cultural practices to reduce any populations can also reduce densities of mealybugs by allowing natural enemies greater access. Flood irrigation and soil disturbance can be used to disrupt ant populations. The plowing under of cover crops in the spring also helps reduce ant populations.
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