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.
|Common name||Amount to use**||REI‡||PHI‡|
|(Example trade name)||(conc.)||(dilute)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|(Entrust)#||2–3 oz||0.5–0.75 oz||4||7|
|(Success)||6–10 fl oz||2–3.3 fl oz||4||7|
|MODE OF ACTION GROUP NUMBER1: 5|
|COMMENTS: To prevent the development of resistance to this product, rotate to a material with a different mode of action Group number after treating two consecutive generations. Residual efficacy is affected by pH, but initial efficacy is not: verify that water pH is greater than 6 and less than 8.|
|**||Dilute rate is the rate per 100 gal water; use 400 gal solution/acre. Apply concentrate in 80–100 gal water/acre, or less if the label allows.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|#||Acceptable for organically grown produce.|
|1||Rotate chemicals with a different mode of action Group number, and do not use products with the same mode of action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|