Grape mealybug update for week ending June 24, 2011
The GMB population is in the adult (female) and ovisac stages, at vineyards we are monitoring from Oak Knoll to St Helena, and into Pope Valley. Nymphs hatching from these ovisacs will move into the clusters to feed.
Last week we began to see more evidence of activity of biological control agents, both parasitic wasps and predators.
For those concerned about GMB as a vector of leafroll viruses, this will be the appropriate timing for insecticide applications.
Spirotetramat (Movento) applications may be most appopriate during this stage (egg development).
The appropriate timing for application of insect growth regulators (Applaud) is at or just after egg hatch. Insect growth regulators are most effective against young mealybugs (1st and 2nd instars).
Contact neonicotinoids (such as foliar applications of Clutch and Venom, Assail, Actara, and others) may be applied at or after egg hatch. Contact insecticides may be applied up to harvest (respecting pre-harvest intervals), although efficacy may be reduced after bunch closure when it is more difficult to contact mealybugs feeding in the clusters.
Organically registered materials also typically have contact activity, so are most appropriate after egg hatch, or during the young instar nymph stages.
Insecticide applications may disrupt natural enemies that attack GMB. Unwarranted insecticide applications should be avoided to conserve natural enemy populations.