QUANTITATIVE RELATIONSHIP BETWEEN STICKY TRAP CATCH AND BEAT TRAY COUNTS OF PEAR PSYLLA (HOMOPTERA, PSYLLIDAE) - SEASONAL, SEX, AND MORPHOTYPIC EFFECTS

Adult pear psylla, Cacopsylla pyricola (Foerster), were monitored with beat trays, yellow sticky traps, and clear sticky traps for 2 yr at 3 orchards to determine whether a general relationship exists between t ray counts and sticky trap catch. Samples were also categorized accord ing to morphotype of the insect (summerform versus winterform), diapau se status of winterforms (diapausing versus postdiapause and reproduct ive), and sex of the insect. Most (42 of 48) of the samples indicated that trap catch varied significantly with tray count (by linear regres sion analysis). However, aside from the fall winterform generation, no general relationship between trap catch and tray count was noted. Res ults suggest that sticky trap counts often had a large behavioral or a ctivity component that obscured density effects. These effects were es pecially noticeable in the spring winterform generation and the summer form generation. Factors affecting sticky trap catch included sex of t he insect, reproductive status, trap color, insect age, and leaf fall. We suggest that these factors, as well as others not explored here (e .g., weather), contributed to the lack of a general relationship betwe en tray and trap counts. Previous work indicates that either method pr edicts damage to the tree; thus, for pest-management decisions, both s ampling methods are useful. However, for more precise questions about absolute densities of adults, we suggest that beat trays should be pre ferred.