The azalea lace bug (ALB), Stephanitis pyrioides (Scott), is an economically important hemipteran pest on azalea and a serious problem to azalea production nurseries in the southeastern United States. Eggs overwinter in midribs of leaves and nymphs hatch in early spring. Adults, appearing black and spiny with netted wings (Schultz and Shetlar, 1994), feed on the underside of leaves through the upper palisade parenchyma of stomates causing significant leaf chlorosis. Chlorosis appears as yellow patches or stippling on the upper leaf surface, which can reduce photosynthesis and gas exchange in response to feeding as a result of stomatal restriction (Buntin et al., 1996).
Plants can protect themselves against insect attack using both physical and chemical mechanisms. Physical modifications to the leaf structure can be an effective barrier against insect pests through the adaptation of leaf surfaces and hairs. Plants can also sequester secondary metabolites in their vascular tissue that provide a chemical defense against insect feeding (Panda and Kush, 1995). We have observed that Rhododendron oldhamii Maxim. ‘Fourth of July’, a cultivar with small stomates, has little ALB feeding. Based on this observation and the fact that lace bugs feed through stomata on the underside of leaves (Ishihara and Kawai, 1981; Mathen et al., 1988), we hypothesize that smaller stomatal size confers to azalea some physical resistance to ALB feeding by restricting access to the feeding site. All Encore Autumn™ cultivars of azaleas have ‘Fourth of July’ as one of their parents. Therefore, we tested Encore™ cultivars as well as other common azalea cultivars from various lineages for resistance to ALB. In this study, we chose to examine the effects of stomatal area and length on ALB feeding preference on 33 commercial cultivars of azalea to determine if these leaf characteristics influence ALB preference. Choice and no-choice ALB feeding bioassays were performed in the laboratory to determine possible varietal feeding preference on azaleas by S. pyrioides.
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