Optimizing Management Guidelines for the Non-Native Azalea Lace Bug on Rhododendron Species in Western Washington

Abstract

The non-native, invasive azalea lace bug, Stephanitis pyrioides (Scott), is one of the most serious insect pests of the genus Rhododendron, especially evergreen azaleas, an especially popular subgenus of Rhododendron. Feeding by nymphs and adults remove chlorophyll from leaves, reducing rates of photosynthesis and transpiration of infested plants, and causes stippling on the top of the leaf, which reduces the aesthetic value of infested plants. Severe infestations can lead to plant death. Introduced to the eastern U.S. from Japan in 1916, its presence in western Washington was confirmed in 2007. Research on azalea lace bug in the Pacific Northwest is extremely limited to date. In my thesis research, I investigated the seasonality of azalea lace bug in western Washington, and developed region-specific degree-day models to optimize sampling efforts and the timing of control measures. I also studied the susceptibility of Rhododendron spp. to azalea lace bug by assessing feeding damage in 71 different species and cultivars. This research provides improved management guidelines for azalea lace bug in the Pacific Northwest, and provides a framework for using host plant resistance in the design of landscapes where Rhododendron spp. are desired.