Relative toxicity of neem products to the earthworm, Lampito mauritii (Templeton) kept in different substrates

摘要

Effect of three substrates, pressmud, neem saw dust and farm yard manure on the toxicity of neem cake and neem seed (in terms of LC_0 LC_(50) and LC_(100) values) to the earthworm, Lampito mauritii was studied. The toxic range observed between 1-hour LC_(50) and 96-hour LC_(50) was 140--65, 135--65 and 140--70 g neen cake pawder/kg dry substrate weight and 135--55, 130--55 and 130--65 g neem seed powder/kg dry substrate weight respectively for the substrates 1 ,2 and 3. Asymptote was reached in the toxicity curves during 72 hours in substrates 1 and 3 respectively mixed with neem cake powder and neem seed powder at a dose, 65 g/kg dry substrate weight and during 96 hour in substrates 2 and 3 mixed with neem cake powder respectively at 65 and ~-Og doses and the substrates 1 and 2 mixed with neem seed powder and 55 g dose due to atrainment of lethal threshold in the toxic mecium; 96-hour LC_0 and 96-hour LC_(100)] doses were also arrived for the earthworm exposed to neem cake and neem seed powders mixed with substrate 1 at 40 and 80, and 30 and 75, substrate 2 at 40 and 85, and 20 and 75, and substrate 3 at 40 and 90, and 30 and 80 g/kg dry substrate weight respectively. From the 96-hour LC_(100) values, it is inferred that the substrate 3 (farm yard manure) has the ability to reduce the toxicity of neem products to Lampito mauritii and can be used as good manure to any crop which requires more neem products for the control of pests. The toxicity results revealed that the neem products exert only a little toxic effect to Lampito mauritii as evidenced by high doses of gram values and hence they may be used as manure to plants or toxicant to insect pests.