Can silicon enhance resistance to azalea lace bug?

The azalea lace bug (Stephanitis pyrioides) causes aesthetic and physiological damage to two heavy weights of the ornamental industry: rhododendrons and azaleas. All plants contain some silicon in their tissues and concentrations vary considerably, with monocots generally accumulating more than dicots. Examples of plant resistance due to silicon supplementation have been documented for decades and explained by various mechanical and chemical mechanisms of action including, but not limited to, increased leaf strength, decreased palatability and digestibility and changes in leaf chemistries.  Rhododendrons were supplemented weekly in 2019 and 2020 for 4 consecutive weeks with calcium silicate, foliar spray or soil drench, and calcium carbonate soil (2019) and soil and foliar (2020). Leaves were assessed for silicon content using pre- and post- supplementation leaf tissue analysis. Nine replicates, each with one plant per treatment plus a control were set up in insect cages and azalea lace bug released and allowed free choice. Compared to the control, silicon via foliar and silicon via soil resulted in a decrease in frass spots and eggs; a separate control for calcium provided similar resistance. There was no evidence of silicon accumulation in supplemented rhododendrons. Further research with no-choice and field experiments will be conducted to assesss calcium silicate mediated resistance to azalea lace bug and practical use for growers and landscapers.