Heavy infestations also greatly weaken pear trees. Pear psylla nymph in honeydew. Pear psylla spend the winter near previously infested pear trees. They return in early spring, typically around late March in the Grand Junction area. Once on the trees, they begin to feed and lay eggs, producing several generations throughout the growing season.
Pear psylla are highly resistant to most available insecticides.
Oil sprays, sometimes combined with an insecticide, can be effective when applied during the dormant season shortly after the pear psylla adults return to the trees. Cooperative Extension codaphone messages in the Western Slope fruit-growing areas can aid accurate timing of pear psylla treatments. Pear psylla problems are greatly lessened in unsprayed orchards, where they are heavily attacked by parasites. Infested fruits also are prone to spoilage. There are naturally occurring populations of apple maggot on the Western Slope.