DIURNAL PATTERNS IN YELLOW TRAP CATCH OF PEAR PSYLLA (HOMOPTERA: PSYLLIDAE): DIFFERENCES BETWEEN SEXES AND MORPHOTYPES

Abstract

AbstractDiumal patterns in yellow sticky trap catch of pear psylla, Cacopsylla pyricola Foerster, are described for the spring (reproductive) winterform generation, summerforms, and the fall (diapausing/dispersing) winterform generation. For each life stage, trap catch of the two sexes is also compared, and sex ratios on sticky traps are contrasted with independent estimates of population sex ratio obtained by beat tray samples. Beat tray estimates of sex ratio showed a slight male bias for both winterform generations (although P = 0.09 for spring winterforms), and a female bias for the summerform samples. Sticky trap catches were significantly male biased for the reproductive generations (i.e. spring winterforms and summerforms). Trap catches of fall winterforms were not different from a 1:1 ratio. The male bias for the reproductive generations may be due to mate-seeking activities of males or to a decrease in activity by egg-laden females. Peak catch for summerforms occurred in the morning, and that of both winter-form generations occurred at midday. There was no evidence that trapping depleted local densities of psylla during a 24-h period.