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University of California Cooperative Extension Vine Mealybug
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Cultural controls |
The vine mealybug is a new pest to most California vineyard regions. It is the target of eradication programs in some regions. For more information on monitoring and controlling vine mealybug, contact your local UCCE Farm Advisor or County Agricultural Commissioner's Office. |
The vine mealybug is found in the Mediterranean regions of Europe, North and South Africa, the Middle East, Argentina, Mexico (near Hermosillo) and California. In 1994, vine mealybug was first identified as a new mealybug pest in California in the Coachella Valley (Riverside Co.). It spread throughout the Coachella Valley and, in 1998, was found in the southern San Joaquin Valley (Kern Co.). From that point, its rapid dispersion into new regions was dramatic; VMB was found in Fresno Co. in 1999, San Luis Obispo Co. in 2001, and El Dorado, Madera, Monterey, Napa, Sacramento, Sonoma, and Stanislaus Counties in 2002. (see map) Circumstantial evidence suggests dispersion is aided by mechanical harvesting equipment, field crews, infested nursery stock from 1998-2000 (see Nursery Controls), and natural dispersion (e.g., birds) (see Cultural Controls). In all grape regions in California, vine mealybug will can cause damage to raisin, table or wine grapes. First, vine mealybug has a number of biological attributes that result in a rapid increase in its density. For example, females can deposit >500 eggs (avg. is ~300 eggs/female); in the San Joaquin Valley, there are 4-7 generations per year as compared with 2-3 for the grape mealybug, leading to overlapping generations; and individual vine mealybug excrete more honeydew that results in excessive sooty mold growth and defoliation. Second, vine mealybug can feed on all parts of the vine throughout the year, with a majority of the overwintering population located underneath the bark of the trunk or underground on the roots. The hidden locations protect mealybugs from most foliar insecticides, from high summer temperatures in the Coachella Valley, and from parasitoids and other natural enemies. Third, vine mealybug has a wide host range and can feed on subtropical (grapes, figs, apples, and citrus) and tropical (dates, bananas, avocados, and mangos) crops as well as a number of common weeds – such as malva, burclover, black nightshade, sowthistle and lambsquarter. However, grape vines appear to be its preferred host throughout the season. Finally, it can vector viral diseases of grapevines. (Return to top)
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Seasonal
abundance & distribution Vine mealybug seasonal abundance and its distribution on the vine can vary dramatically throughout California, dependent on temperatures and vine condition. While we have found vine mealybug on all parts of the vine at any time of the season, there are clear dispersal and abundance patterns, which influences the amount of damage and the effectiveness of chemical and biological control. For example, in the Coachella Valley the majority of the vine mealybug population overwinters on the roots and lower trunk sections. As temperatures warm, vine mealybug density increases rapidly to a peak in April and May (See Figure 1). Accompanying the increased density is movement up the vine, from the roots and lower trunk to the leaves and grape clusters. Control becomes a race between harvest time and when the vine mealybug reaches the clusters. With hot summer temperatures, the population abundance decreases and again is found primarily on the lower trunk sections and roots. There is another density increase in fall, before the overwintering period. In the San Joaquin Valley, the vine mealybug population also overwinters on the roots and lower trunk and the population continues to move up the vine to the leaves and bunches, as the temperatures warm in spring and summer. Unlike in the Coachella Valley, mealybug abundance continues to increase and remain on the leaves until August (see Figure 2). The late-season reduction was not accompanied by an increase in summer temperatures but was associated with increased parasitism levels (see Biological Controls). All stages were found throughout the summer feeding on leaves and canes in exposed locations, suggesting that San Joaquin Valley temperatures had little affect on vine mealybug densities. We currently have no information on vine mealybug seasonal abundance and distribution in the Central Coast, North Coast or Central Interior regions, but assume VMB will follow a pattern similar to the San Joaquin Valley, resulting in considerable damage. Because VMB densities are still low in these regions, eradication programs are being considered. (Return to top) |
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The best method to prevent damage from vine mealybug is to keep the pest out of the vineyard or to chemically treat populations when the infestation just begins. Mealybugs are difficult to sample because they are often hidden under bark or underground. Look for "signs" of mealybug presence such as foraging ants, honeydew or "wet" bark, and a white wax protruding from underneath the bark. Still, these methods are time consuming. Until recently, visual sampling methods were the only way to spot new infestation, and they were far too labor intensive. In 2001, a faster and effective method to monitor VMB was developed, based on a synthetic VMB sex pheromone that females use to attract winged adult males. When the VMB population density is small (a new infestation), using this sex pheromone to attract the winged male is far more efficient than trying to search 1000s of vines for hidden females. The pheromone has been synthetically produced and, in field tests, traps baited with the synthetic pheromone were attractive for two months, had an effective range of more than 300 feet (wind-aided), and had counts that could be correlated with VMB densities in the vineyard. Pheromone lures are available from Suterra Ò (Suterra LLC, phone: 541 388-3688, website <suterra.com>). The preferred pheromone trap is a Pherocon Delta IIID sticky traps (Trécé Inc., phone: 831-758-0204, website <trece.com>) or (Suterra LLC). These 3-dimensional traps provided better adult male VMB catch and lower “unwanted” insect catch as compared with flat traps. One lure is used per trap. Traps should be checked every two weeks during the growing season and monthly thereafter. Lures should be changed at least every 4-8 weeks. Traps need to be changed only when they are old or vine mealybug males are collected (so that the male VMB can be counted). If no male mealybugs are found, new lures can be placed into old traps. Traps should be hung at or above the cordon and near the center of the vine. We found the trellis wires make a good attachment point. The traps can be placed in the canopy to get some protection from wind and equipment, but the open ends should be exposed so that VMB males can easily fly rather than walk into the hollowed center. The trap position may have to be changed during the season to avoid interference with standard management operations. VMB males in the traps will lose their "white wax" on the cerci (or tail). Look for a single pair of wings, a small "V" tail, and long antennae. The brown insects are a bit smaller than adult thrips, with longer antennae and wings. Remember that the "close up" photographs make the insects look larger and easily identified. Once on the sticky trap for a couple of days they lose much of their identity. On this trap there are 12 VMB males near an adult leafhopper. For this reason, replace the traps when they get dirty or full. |
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Trap Placement and Counts We suggest 2 traps for each 20-40 ac block monitored. Put one trap near the center of the block and the other in a "high" traffic area (near the packing house, near roads or intersections, near equipment storage areas or field shops). In established, older vineyards, new infestations have been found near replants, the row ends, home landscaping, and bird habitats. There is no reason to bury the trap deep inside the vine or well within a vineyard block such that crews can not easily find and monitor the traps. (e.g., near a packing house). If more traps are used, they should be placed at least 30 rows apart (about 200-300 feet) and 10 vines inside each block. (Return to top) |
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Male Flight Periods In the Coachella Valley, the male flight period goes from about March through August. In the San Joaquin Valley, the flight will run from May through October. Females often mate in the fall - so the first male flight the following spring may be after vine mealybug activity begins and. (Return to top)
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Trap Counts Traps should be checked every 2-4 weeks, depending on mealybug density and vineyard susceptibility. In heavily infested vineyards, we have found >2000 males per trap per week. Typically, an infested vineyard will have between 20-300 males per trap per week. If >10 VMB males are found per week in a trap, then the infestation may be in another block. The traps are more sensitive than most visual sampling methods, so trap counts <10 VMB per week may be from neighboring or even distant blocks (up to ½ mile away as the males can be wind-blown). Current research is investigating new methods to increase trap efficiency. In those counties where vine mealybug is not know to commonly occur (see map), the vineyard manager should contact the County Agricultural Commissioner’s office and UCCE Farm Advisor to get a positive identification of trapped mealybugs and discuss management decisions and compliance agreements as necessary. (Return to top)
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A number of insecticides can be used to kill exposed vine mealybug, especially the small stages. The hidden portion of the population is harder to control. For this reason, vine mealybug is difficult to control once it has become well-established in the vineyard. Systemic insecticides (e.g., AdmireÒ) that reach all parts of the vine have been the most effective. A control program to eradicate vine mealybug would include:
For more information on chemical controls, contact your local UCCE Farm Advisor or County Agriculture Commissioner. Registered materials are listed at: http://www.ipm.ucdavis.edu/PMG/r302301911.html (Return to top)
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A number of predators and parasitoids have been recorded attacking vine mealybug in California. Most of the common predators will feed on any of the vineyard mealybug species and our discussed as a group (see Natural Enemies).
The vine mealybug is closely related to the citrus mealybug, and shares a number of parasitoid species that are present in California. Additionally, foreign exploration for new parasitoids added to the parasitoid complex. For a complete list of mealybug parasitoids see Natural Enemies.
Anagyrus pseudococci is the most common parasitoid. The adult female is about 2 mm in length and golden-brown with long antennae that are black at the base and then white to the ends. The male is smaller (1 mm), dark-colored with hairy antennae. In the lab, Anagyrus pseudococci attacked 2nd, 3rd and adult stage vine mealybug at a rate of 19, 33, and 48%, respectively, indicating that it prefers larger mealybugs. Parasitoid develop time is about 18 days during the summer. In field trials, this parasitoid attacked 70-95% of the exposed vine mealybugs in August and September samples in the San Joaquin Valley. Parasitism in the Coachella Valley was lower, never exceeding 20% (unless parasitoid were released). The difference in parasitism levels between these two regions in largely attributed to the greater period of mealybug exposure to parasitoids in the San Joaquin Valley (see Vine Mealybug Biology).
Parasitism rates can be improved by releasing Anagyrus pseudococci early in the season. This parasite is commercially available (phone: 888-767-0120, e-mail: XFARINC@aol.com). Studies suggest early season-release of 20,000 parasitoids per acre has increased parasitism and reduced crop damage, although this research is still in progress and may vary greatly among vineyard regions.
Leptomastidea abnormis was recently released in the Coachella and San Joaquin Valleys. The adult is slender, about 2 mm, and patterned white and black, including the antennae. Leptomastidea abnormis is not as common as Anagyrus pseudococci and currently accounts for <10% of the parasitism. In the lab, Leptomastidea abnormis attacked 2nd, 3rd and adult stage vine mealybug at a rate of 61, 32 and 7%, respectively, indicating that it preferred smaller mealybugs. (Return to top)
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