How to Manage Pests
UC Pest Management Guidelines
DESCRIPTION OF THE PEST
California pear sawflies overwinter as pupae in the soil. In early spring, adults emerge and lay eggs, which usually hatch by petal fall. Larvae are about the same green color as the leaves and are difficult to see because they rest inside the edges of the feeding area. Sawfly larvae can be distinguished from moth larvae by their spherical head capsule; moth larvae have flattened head capsules. Maturing larvae are about 0.5 inch long. There is only one generation per year and larvae are present in trees during spring months only. The California pear sawfly can be distinguished from the pear sawfly (i.e., the pearslug) by the lack of a slimy coating covering its body.
These pests are foliage feeders and do not attack fruit. Most eggs hatch by petal fall and larvae immediately begin feeding on leaf tissue in a circular pattern within or along leaf edges, leaving round or oval holes. Several larvae can consume an entire leaf, leaving only the midrib. In heavy numbers sawflies are capable of defoliating orchards in several weeks, but this rarely occurs in California.
The California pear sawfly is distributed throughout pear-growing regions in the state but is a minor pest of pears. Generally it only affects backyard trees, or commercial trees where treatment was not applied during the bloom period. Treat only if justified by monitoring results.
Monitoring and Treatment Decisions
Inspect foliage for small holes at petal fall or shortly after. Randomly sample one leaf on each of 100 trees in a block. If there are less than six infested leaves per block, no action is necessary. If 6 to 24 leaves are found infested, monitor the infestation weekly for further increases in numbers and damage. When 25 or more of the sampled leaves are infested, either advance the first codling moth cover spray or apply a treatment aimed at this pest.
UC IPM Pest Management Guidelines:
Insects and Mites
L. G. Varela, UC IPM Program, UC Cooperative Extension, Sonoma County