Exploring silicon supplementation as an alternative tool to enhance resistance to azalea lace bug (Stephanitis pyrioides)

Potted rhododendrons were supplemented with calcium silicate to determine if silicon enhances resistance to the invasive azalea lace bug.  The first two years, four groups of rhododendrons were supplemented with a foliar spray or a soil drench with either calcium silicate or calcium carbonate and subsequently tested for resistance in a greenhouse. A choice trial the first year showed frass spots and oviposition were reduced with calcium silicate but reduction also occurred with the calcium carbonate treatment the second year. Foliar spray showed a slight advantage over the soil drench for both supplements. There was no difference between supplemented and control groups in no-choice trials. In 2021, plants were treated with both supplements only as a foliar spray.  They were placed in mature landscapes next to heavily infested rhododendrons at the beginning of the summer and assessed for leaf damage and lace bug population.