Pest description and crop damage The adult female is wingless and can be up to 0.2 inch long. It has a well-developed ring of waxy filaments around the sides of its body. The nymphs (or young crawlers) are purplish and covered with a powdery wax coating. As they get older, the coating gets thicker, and a fringe of wax filaments develops. Mealybug damage primarily results from the honeydew which is secreted. Honeydew is cast off in small drops and falls down through the canopy. When it lands on fruit it serves as a substrate for sooty mold which causes a coarse, black russet to form. This is similar to pear psylla russeting, though mealybug russeting is scattered over the fruit surface, while honeydew from psylla is in patches or streaks. In addition to russeting due to honeydew, populations of mealybug can result in infestation of the calyx and associated rot in storage.
Biology and life history Grape mealybugs overwinter as eggs or first instar crawlers in egg sacs beneath bark scales and in cracks. Crawlers start emerging from egg sacs at the beginning of bud swell and begin feeding on the bases of buds. When buds open they go directly to new shoots and leaves. Once settled, the crawlers start feeding and become progressively harder to kill. First generation nymphs mature during late June and July in the Northwest. Adult males appear first, mate and die. Receptive females release a pheromone to attract males. Mated females migrate to sheltered areas, lay eggs and die in the egg sac. In warmer areas a second generation matures in late August and September. Nymphs of this generation sometimes settle around the stem end of the fruit or in the fruit calyx.
Little research has been done to date 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 on mealybugs in orchards that use fewer broad-spectrum chemicals. A ladybeetle, the "mealybug destroyer" (Cryptolaemus montrouzieri), is considered an effective predator of mealybugs worldwide. It is available from some insectaries.
Management-chemical control: HOME USE
- azadirachtin (neem oil)-Products containing neem extract may be phytotoxic to some pear cultivars. Some formulations are OMRI-listed for organic use.
- pyrethrins-Some formulations are OMRI-listed for organic use. Highly toxic to bees.
Management-chemical control: COMMERCIAL USE
Usually, it takes two sprays to cover emergence (pink and petal fall). High volumes of water and thorough coverage are essential for control. Sprays applied when second-generation crawlers emerge in early July may help prevent fruit infestation in the calyx end.
- acetamiprid (Assail) at 1.1 to 3.4 oz/a. REI 12 hr. PHI 7 days. Do not exceed four applications or 13.5 oz per season.
- buprofezin (Centaur WDG) at 34.5 to 46.0 oz/a. REI 12 hr. PHI 14 days. Do not exceed two applications or 69 oz per season.
- diazinon (Diazinon 50W) at 4 lb/a. REI 4 days. PHI 21 days. Applicators must use an enclosed cab, see label for details. One dormant and one in-season foliar application allowed with a minimum of 70 days between applications.
- imidacloprid (Prey 1.6) at 20 fl oz/a. REI 12 hr. PHI 7 days. Only apply post-bloom. Repeated use may induce spider mite buildup.
- phosmet (Imidan 70W) at 3.5 to 5.75 lb/a. REI 7 days. PHI 7 days.
- spirotetramat (Ultor) at 10 to 14 oz/a. PHI 7 days. REI 24 hr. PHI 7 days. Minimum 14 days between applications. Must be used with an adjuvant; see label. Do not apply prior to petal fall.