Acidulation to improve the function of controlled-release insecticide granules for canegrub control in soil

Zonal acidulation of soil around controlled-release (CR) granules substantially increases concentration of chlorpyrifos insecticide in both the granules and surrounding soil. This strategy is being tested as a means to gain or improve control of sugarcane whitegrub with CR-formulated chlorpyrifos, particularly for situations where the granules are prone to premature degradation. Acidulation methods included applying ammonium sulfate and sulfur to soil in the same zone as CR granules, and sulfur-coating CR granules. Treatments were tested singly and in combination for their effects on soil pH and chlorpyrifos concentration in both CR granules and the surrounding soil. Initial responses from these treatments in micro-plots are being confirmed in larger field-scale plots.