Grape-Grape mealybug

Pseudococcus maritimus

Pest description and crop damage The grape mealybug has a soft, oval, flattened, distinctly segmented body. The adult female is 0.25 to 0.5 inch long, pink to dark purple, and with a white, mealy, wax secretion. Long posterior filaments along the lateral margin of the body become progressively shorter toward the head. Eggs are yellow to orange and laid in cottony egg sacs. Crawlers that hatch from them are tiny (0.06 to 0.12 inch long), yellow to brown. Males and females are similar in early instar stages. Males pass through three nymphal instars, then form a cottony cocoon about 0.12 inch long in which the pupa is formed. All stages of the female are similar, varying in size only. The crawler stage of this pest is most mobile.

Statewide surveys show that mealybugs can be problematic in southern and western grape-growing regions of Oregon. In these regions, mealybugs may come into direct contact with grape clusters resulting in direct crop losses. Grapes grown in the Willamette Valley of Oregon don't seem to have this severe problem of cluster contamination. Grape mealybug contaminates fruit with cottony egg clusters, eggs, immature stages, adults, and honeydew. Sooty mold (a black fungus) may grow on the honeydew. Of most concern in all regions is that grape mealybugs are important vectors of the grapevine leafroll virus. This insect can therefore spread the virus within and across vineyards. The virus may reduce crop yields and fruit quality. For this reason, it is important that growers know the status of mealybug presence in their vineyards.

Biology and life history Grape mealybugs of all life stages overwinter on the cordon section of vines and under the loose bark. These are the preferred feeding sites, making them inconspicuous to growers. Increasing summer populations move to new tissue growth to feed. Eggs can be laid on all plant parts during the season. Generations may overlap during the latter part of the season making control more difficult. As populations build, migrating mealybug populations may move to clusters during July and August, causing direct crop damage. Some females maturing in mid- to late August lay their eggs on fruit and leaves. Most late summer populations return to old wood in the cordon section of vines and under the loose bark to overwinter.

Sampling and thresholds Control thresholds have not been defined. The number of late season migrating mealybugs increase the likelihood of contamination with vine leafroll virus and warrant control. Commercial pheromone traps are available to aid in effective monitoring for mealybugs. Vineyards with known virus infection should be monitored for the presence of mealybug populations using pheromone traps starting during the late dormant period.

Management-biological control

Little research has been done in Oregon on the effectiveness of natural enemies in keeping mealybug populations at levels below economic damage. Parasitic wasps, predatory bugs, predatory beetles, lacewings, and spiders can take a considerable toll of mealybugs in vineyards that use few broad-spectrum chemicals. A lady beetle, the "mealybug destroyer" (Cryptolaemus montrouzieri), is considered an effective predator of mealybugs worldwide. It has been seen in recent seasons in some Washington vineyards and is available for release from some insectaries.

Management-cultural control

To prevent movement and spread of mealybugs and virus within and between vineyards, it is critical to restrict movement of fruit and manage winery pomace (grape waste) properly.

Management-chemical control: HOME USE

Dormant-season spray

  • superior-type oil

Growing-season spray

  • acetamiprid
  • cyfluthrin
  • imidacloprid
  • pyrethrins (often used in a mix with other ingredients)-Some formulations are OMRI-listed for organic use.

Management-chemical control: COMMERCIAL USE

Dormant season

A dormant spray with horticultural oil and/or the use of buprofezin (Applaud) causes the least disruption to IPM. Control is most effective when mealybugs are in the crawler stage, and Applaud is the recommended treatment. Direct spray the trunk, canes, or cordons using sufficient water to loosen bark and drive the pesticide into cracks. If infestations are patchy, use spot-treat only. Frequent use of imidacloprid or chlorpyrifos can result in spider mite outbreaks.

Early season

  • buprofezin (Applaud) at 0.40 to 0.53 lb ai/a. PHI 7 days. Apply at early stages of crawler emergence by ground using 50 to 200 gal/a water, depending on the size of the grape plants. Use of a higher volume of water will ensure better coverage, especially under adverse conditions such as hot, dry weather and/or a dense canopy. Do not exceed 1.05 lb ai/a per season. Allow at least 14 days between applications. Group 16 insecticide.
  • Chromobacterium subtsugae strain PRAA4 (Grandevo) at 2 to 3 lb product per acre. PHI 0 days. OMRI-listed for organic use.
  • chlorpyrifos (Lorsban Advanced) at 0.94 to 1.88 lb ai/a in at least 50 gal/a water using ground equipment only. For use in Idaho and Washington only (24c labels: ID-010004 and WA-090002). PHI 35 days. Use 0.94 lb ai/a for normal infestations, prior to bloom stage of growth. Use 1.88 lb ai/a for high infestations only as a dormant or late dormant application. Do not exceed 1.88 lb ai/a or two applications per crop growing season. Do not apply this product through any type of irrigation system. Leaf yellowing may occur with applications made post-bud break in Concord grapes. This is a restricted use pesticide (organophosphate insecticide). Group 1B insecticide.
  • horticultural oil (several brands)-Consult label for rate. Apply oil at 200 to 300 gal/a. Apply in late March or early April. Do not apply oil after budbreak. These compounds generally do not lead to good levels of control.
  • imidacloprid (Admire Pro and other brands)
    • Soil application at 0.25 to 0.5 lb ai/a. PHI 30 days. Apply in one or two drip irrigations between budbreak and pea-size stage of berry development. Consult label for restrictions. Do not apply more than 0.5 lb ai/a per year. Group 4A insecticide.
    • Foliar application at 0.036 to 0.05 lb ai/a. PHI 0 days. Do not exceed 0.1 lb ai/a per year. Allow 14 days between applications. Group 4 A insecticide.
  • phosmet (Imidan 70W) at 1.0 to 1.5 lb ai/a. PHI 7-14 days depending on rate; see label. Apply as a delayed dormant (pre-budbreak) spray with a spreader sticker. REI 14 days. Do not use more than 4.55 lb ai/a each year. Phosmet has not shown good control in Oregon. May not apply during grapevine dormancy. This is an organophosphate insecticide and use should be limited. Group 1B insecticide.
  • spirotetramat (Movento) at 0.10 to 0.13 lb ai/a. PHI 7 days. Ensure that there is adequate foliage for absorption of the compound. Allow 30 days between applications. Do not exceed 0.2 lb ai/a per season. A high quality spreader should be used to enhance penetration into foliage; see label for more details on which adjuvants to use or avoid. Group 23 insecticide.

Summer

  • buprofezin (Applaud 70DF) at 0.40 to 0.53 lb ai/a. PHI 7 days. Do not exceed 1.05 lb ai/a per season. Allow at least 14 days between applications. Apply by ground applicator using a minimum of 50 gal/a water, depending on grapevine size. Using a higher volume of water assures better coverage, especially under adverse conditions such as hot, dry weather and/or a dense canopy. Do not exceed two applications per crop cycle. Group 16 insecticide.
  • Chromobacterium subtsugae strain PRAA4 (Grandevo) at 2 to 3 lb product per acre. PHI 0 days. OMRI-listed for organic use.
  • imidacloprid (Admire Pro and other brands) at 0.036 to 0.05 lb ai/a. Foliar application. PHI 0 days. Do not exceed 0.1 lb ai/a per year. Allow 14 days between applications. Group 4 A insecticide.
  • malathion (Malathion 8E) up to 1.88 lb ai/a. PHI 3 days. Make summer application at first sign of honeydew on fruit (early to mid-July). Group 1B insecticide. This is an organophosphate insecticide. Malathion has not shown good control in Oregon.
  • phosmet (Imidan 70-W) at 1.0 lb ai/a applied when fruit sizing and pest is present on fruit and/or leaves. Ensure adequate coverage of fruit and leaves for best result. PHI 7 days. REI 14 days. Do not apply more than 4.55 lb ai/a annually. Supplemental label (FIFRA 2(ee) for WA. Group 1B insecticide. This is an organophosphate insecticide and use should be limited. Phosmet has not shown good control in Oregon.
  • spirotetramat (Movento) at 0.10 to 0.13 lb ai/a. PHI 7 days. Ensure that there is adequate foliage for absorption of the compound. Allow 30 days between applications. Do not exceed 0.2 lb ai/a per season. A quality spreader should be used to enhance penetration into foliage; see label for more details on which adjuvants to use or avoid. Do not exceed 0.2 lb ai/a per season. Group 23 insecticide.
  • thiamethoxam + chlorantraniliprole (Voliam Flexi) at 0.11 lb ai/a. PHI 14 days. Allow 14 days between applications. Do not apply more than 0.109 lb ai/a of thiamethoxam or 0.2 lb ai/a of chlorantraniliprole per season (2 applications) per season. Groups 4A and 28 insecticides.

For more information:

Prevention and Management of Grapevine Leafroll Virus and Mealybugs in Oregon Vineyards (https://catalog.extension.oregonstate.edu/em8990)

Distribution and Monitoring of Grape Mealybug: A Key Vector of Grapevine Leafroll Disease in Oregon (https://catalog.extension.oregonstate.edu/em9092)

Field Monitoring for Grapevine Leafroll Virus and Mealybug in Pacific Northwest Vineyards (https://catalog.extension.oregonstate.edu/em8985)