Safety Evaluation Of Insecticides Applied In Paddy Field To Spiders

Chemical control has always been the main way of pest management with efficiency and simplification. However, abusing chemical agents will not only destroy the natural control against pest populations, but also disturb the balance of ecosystem. So it makes great sense to properly apply chemical agents and keep the balance between chemical control and biological control. This paper mainly discussed the safety of eight common insecticides to spiders through laboratory and field experiments. The results were as follows:1. Study on biological characteristics of Hylyphantes graminicola and toxicity of insecticides against Hylyphantes graminicolaBiological characteristics of Hylyphantes graminicola, duration before each oviposition, development duration, predating, growth, hunger and drought resistance ability, were studied in lab conditions. Based on these studies, the experiment method of pymetrozine, buprofezin and chlorantraniliprole was discussed in determining the time for result record.25-27℃was the proper tempetature for H. graminicola rearing in lab, the predating of cotton bollworm and fruit fly made H. graminicola grow evidently. Time for drought resistance was8.94days.2days can best reflect the toxicity of pymetrozine, buprofezin and chlorantraniliprole against H. graminicola.2. Laboratory safety evaluation of eight insecticides against predating natural enemies, Hylyphantes graminicola, Pirata subpiraticus and Coleosoma octomaculatumThe toxicity of eight insecticides against predating natural enemies, the spider Hytyphantes graminicolum, Pirata subpiraticus and Coleosoma octomaculatum, was determined in the laboratory. The toxicity was evaluated by Risk Quotient (RQ=LC50/The recommended concentration). To H. graminicola and C. octomaculatum, pymetrozine, buprofezin, thiamethoxam, isoprocarb and chlorantraniliprole were low risk insecticides (RQ>5.00), to P. subpiraticus, isoprocarb was moderate risk insecticide (RQ=0.89). To all of them, emamectin benzoate was moderate to high risk insecticide (RQ=0.14,2.20and0.08, respectively), chlopyrifos was moderate to exteremely high risk insecticide (RQ=0.07,0.04and0.88, respectively).Abamectin was high to extremely high risk insecticide to H. graminicola and C. octomaculatum (RQ=0.19and0.01, respectively).3. The field risk of chlopyrifos, isoprocarb and emamectin benzoate against spiders and parasitoidsThe field risk of chlopyrifos, isoprocarb and emamectin benzoate against spiders and parasitoids was evaluated by spraying method under field condition. Isoprocarb was safe insecticide to Hylyphantes graminicola, but not safe to Pirata subpiraticus, with mortality of80.6%. All three insecticides were not safe to both spiders, with mortality of47.1%to100%. To Trichogramma japonicum, chlopyrifors was not safe, the emergency rate reduced apparently with20.5%-58.0%in all developing stages of T. japonicum. Isoprocarb and emamectin benzoate were safer than chlorpyrifos. To Anagrus nilapavatae, emamectin benzoate was not safe, compared with chloryforis and isoprocarb, the parasitism rate treated by emamectin benzoate was21.9%, which was significantly different with that of control.