Effect of green-cane harvesting and trash blanketing on numbers of greyback canegrub

Lower population densities of greyback canegrub (Dermolepida albohirtum) were recorded in ratoon crops managed by green cane harvesting and trash blanketing (GCTB). In a replicated trial at Tully Sugar Experiment Station, fewer grubs were found in GCTB (0.9 per stool) compared to buried trash (1.7 per stool) and burnt trash (1.6 per stool). Initial numbers of small canegrubs were similar in each treatment. Rate of development of canegrubs was slightly lower under GCTB compared to burnt trash. Six unreplicated trials compared GCTB with burnt trash. Three trials in the Burdekin and one in Tully had at least three times as many late-stage canegrubs per stool in crops with burnt trash compared to GCTB. One Burdekin site gave a 27% increase in tonnage of cane, and 30% higher sugar yield in GCTB compared to burnt trash. The presence of grass weeds may have increased numbers of canegrubs in GCTB at two Budekin sites.