THE LETHAL AND TERATOGENIC EFFECTS OF BEN OMYL ON THE EARTHWORM BIMASTUS-PARVUS EISEN

Experiments were conducted to study the lethal and teratogenic effects of benomyl on the earthworm Bimastus parvus Eisen. The LC50 ranged fr om 0.0128 to 0.0363 mg/cm2 for benomyl based on contact filter paper t est. Lethal effects of benomyl on earthworms were significantly affect ed by the soil substrares, age of worms and different sources of organ ic fertilizers. Significant difference in toxic effect of benmoyl to e arthworms in the six soil substrates was observed. The highest.mortali ty was found in Chupei sandy loam soil, next were Taofeng loam soil, W ufung sandy loam soil, Chungli loam soil, Houlung sandy loam soil, res pectively, and Hsinpu clay loam exhibited the lowest mortality. Mature worms exhibited significantly lower mortality (p less-than-or-equal-t o 0.05) than middle and adult worms. Mortality flucctuation due to ben omyl was also affected by organic fertilizer treatments, application o f 25/ha cattle mannure exhibited the highest mortality and rice straw at 2t/ha the lowest mortality. Teratogenic effects were found in worms exposed to benomyl by external surface contact after amputation. Howe ver, differences in percent bud formation and anomalies were found bet ween treatments with different concentrations of benomyl; higher expos ure to benomyl corresponded to a decrease in the bud formation and an increase in the anomalies. Timing of segmental delineation of the bud was delayed as the concentration was increased and the percentage of b ud delineation for benomyl treatments was one time higher than the che ck. No differences in concentration responses existed in segmental del ineation of the bud.