[Control of chironomids in water by immobilized Bacillus thuringiensis var. israelensis de Barjac]

A strain from Bacillus thuringiensis var. israelensis de Barjac (B. t. i), having a fatal toxicity to chironomids, was immobilized in the PVA-H3BO3 gel beads confected with a bit of sodium alginate and activated carbon. The result showed that optimal weight ratios were 10% PVA, 1% sodium alginate and 20% activated carbon, respectively. When 4% calcium chloride saturated boric acid solution (pH=6.7) was used as gelatin agent for gelating 24 h, the produced gel beads had good performance in mechanical strength. This method is proved to be simple and cheap. The toxicity of the beads to chironomids is high and the release is slow.