Insect Concerns at Petal Fall

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Rosy apple aphid damage on apple leavesPetal fall is an important time for control of the plum curculio and first generation oriental fruit moth (OFM). For both insects, a single insecticide application generally does an excellent job of minimizing damage by these pests. However, the choice of insecticides to use will depend on whether mating disruption is being used for OFM, and if an insecticide effective against rosy apple aphid was applied before bloom. If mating disruption is being used, it is not necessary to use an insecticide effective against OFM. Also, if an insecticide effective against rosy apple aphid (RAA) was not used before bloom, there is still time at petal fall to control that pest, in which case it would be wise to choose a product that also has activity against RAA (see chart below).

A word of caution: most of the insecticides recommended at petal fall are toxic to bees, so do not be overly anxious to make this application if trees still are still actively flowering and bees are foraging in the orchard. Waiting a week will not significantly affect the level of control achieved with this application.

There have also been questions about how well Sevin used for thinning at this time will control plum curculio and OFM. In most situations the amount used for thinning is too low for effective control of plum curculio or OFM. For OFM, a minimum of 1 lb AI/acre (1 qt of formulated product), and for plum curculio the rate should be 2 lbs AI/A (2 qt).

Finally, for those using post bloom applications of Esteem or Centaur for San Jose scale control, there is a relatively wide window when this application can be made and still provide excellent control. Anywhere from petal fall to about second cover is effective, with first cover being the optimum timing.

Relative Efficacy Chart of Petal Fall Insecticide Options for Petal Fall Sprays
(– = No activity, P = Poor, F = Fair, G = Good, E= Excellent)
Insecticide Plum Curculio OFM RAA Toxicity to Bees
Actara E F E Highly toxic
Assail F G E Mod. toxic
Avaunt E G Mod. toxic
Imidacloprid P P E Highly toxic
Imidan E E Mod. toxic
Voliam Flexi E E E Highly toxic