WITHIN-TREE DISTRIBUTION OF PEAR THRIPS (THYSANOPTERA, THRIPIDAE) IN SUGAR MAPLE

Within-tree distribution of pear thrips, Taeniothrips inconsequens (Uz el), in sugar maple, Acer saccharum Marsh., was determined in six nonf lowering trees in 1990 and six flowering trees in 1992. During budburs t, vegetative (1990) and flower (1992) buds were sampled from four car dinal quadrants, two canopy positions (inside and outside), and three crown levels (upper, middle, and lower) of sugar maples in a plantatio n in central Pennsylvania and examined for thrips eggs and adults. Alm ost all thrips adults were identified as T. inconsequens (94.9% in 199 0 and 97.0% in 1992) and all eggs were likely to be from T. inconseque ns because of their position in bud tissues and their morphology. Few larvae were present. Thrips eggs and adults were found in vegetative a nd flower buds throughout all levels, positions and quadrants. There w ere few significant differences in relation to any part of the tree in either year. In 1990 significantly more eggs (but not adults) were fo und in the middle level, compared with the lower and the upper levels. There was a significant interaction between height and quadrant for e ggs (but not adults) in 1992. Within-tree distribution of pear thrips is likely to be affected by the synchrony between thrips emergence fro m overwintering sites and the timing of budburst in a particular posit ion within the tree, and the distribution and density of flowers.