Azalea growth in response to azalea lace bug (Heteroptera : Tingidae) feeding

The effects of analea lace bug, Stephanitis pyrioides (Scott), feeding inju ry on azalea growth and development were investigated using 'Girard's Rose' azaleas during a 2-yr field study in Georgia. Low, medium, and high injury treatments, which corresponded to 6, 8, and 14% maximum canopy area injury , were compared with control azaleas that received no lace bug infestation. Flower number, whole-shrub leaf and stem dry mass, and dry mass and size o f new growth tissues were unaffected by treatments. In contrast, growth ind ex measurements, a general measure of variability frequently used for horti cultural differentiation, showed significant reductions for all treatments in comparison to control azaleas after 20 wk. Though not directly quantifie d, this apparent discrepancy may be explained as an artifact of lace bug fe eding-induced leaf abscission. Growth index measurements had considerable v ariability and may not be the most reliable measurement of size. In July 19 98, plant canopy densities among azaleas maintained in the high injury trea tments were approximate to 15% less full than the canopies of control shrub s. Predaceous insects had a significant negative association with azalea la ce bug number during the 2-yr study. Flower and new tissue production, meas ured destructively during two growing seasons, revealed azalea tolerance to 14% of maximum canopy area lace bug feeding-injury levels.