Pear psylla adults are among the earliest pests to appear in tree fruit crops, and indeed after the warm temperatures of the past week adults were found to be active in southern counties. Oviposition is surely not far off since the first eggs are usually seen by mid-March. So it’s not too soon to start planning for early season control measures.
Dormant oil applications are a standard practice for early season psylla control. Unlike applications made for scale control and mite suppression, oil (while some egg mortality is observed) acts less as an insecticide and more as a method of exclusion. Adults prefer not to lay eggs on oily surfaces. Therefore oil needs to be applied as early as weather conditions permit. Usually the first applications are made in southern counties from mid to late March. Our standard recommendation has always been applications of dormant oil plus an insecticide, usually a pyrethroid. At the 2013 Mid-Atlantic Fruit and Vegetable Convention Dr. Peter Shearer gave an excellent presentation summarizing Pear Psylla Management in Oregon. There was much new information presented regarding sub-lethal effects of insecticides on natural enemies of pear psylla. One piece of information that was of special interest to me was the use of combinations of dormant oil and sulfur compounds for post harvest and early season knockdown of adult psylla populations. One to two applications 4-6 gals of oil + 10 gals of lime sulfur OR 15-20 # of 80% dry flowable sulfur is recommended in the dormant stages. This combination is said to knock down up to 80% of adult populations. Sulfur/oil combinations should be avoided if the weather is hot. Likewise follow the label precautions for oil applications when cold temperatures are expected. If possible it is best to make applications before the oviposition period begins which can be as early as the first week of March.
On the west coast where area wide mating disruption for codling moth control is practiced psylla can be completely controlled by beneficial insects. Mating disruption is not practical for our small NJ pear plantings unless applied on a large scale including adjacent apple blocks. However, a program that can avoid early season insecticides might preserve enough beneficial insects to help suppress the first generation. Good control of the first generation usually goes a long way toward avoiding summer outbreaks. Integrating sulfur into dormant season sprays along with two applications of Surround @ 25-50#/acre applications in pre-bloom and post bloom sprays, followed by careful selection of summer insecticides may help to make psylla management easier by conserving beneficial insects and reducing the risk of resistance.
While surround acts as a repellent to PC and can give fair to good control, an insecticide will likely be needed for acceptable plum curculio (PC) control. The Oregon Tree Fruit Pest Management Guide (page 23) tells us that with the possible exception of indoxacarb (Avaunt), insecticides that have efficacy against PC are highly toxic to the mirid D. breavis, an important predator of pear psylla in the west. D. breavis is not found in the east however a closely related mirid species is present that also feeds on pear psylla. Although it hasn’t been studied as extensively, insecticides toxic to west coast mirids are likely to be just as toxic to those found in the east. Since PC moves into orchards from overwintering sites (assuming control has been good in previous years) border applications with an effective residual material applied pre-bloom and from petal fall through early June should improve the efficacy of full block applications of surround, while conserving natural enemies in the orchard interior.