Abstract
The effect of pear psylla, Psylla pyricola Forster, feeding on the growth and survival of Bartlett pear trees on Bartlett seedling and Pyrus ussuriensis Maxim. seedling rootstocks, was studied in an orchard planting of 400 trees during the first 4 years after planting. Half the trees on each rootstock were exposed to uncontrolled populations while sprays were applied to the remaining trees to control this insect. Trees on Bartlett seedling rootstocks grew more than those on P. ussuriensis rootstocks in both the sprayed and unsprayed plots. Trees on both rootstocks grew more in plots sprayed to control psylla than comparable trees in unsprayed plots. The number of tree deaths owing to quick decline was greater for trees exposed to pear psylla than for those sprayed to control this insect.
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