Safety Studies Of 5 Insecticides On Main Predatory Natural Enemies In Single-Cropping Paddy Fields

Instead of natural control to the pests, long-term and frequent application of chemical insecticides had destroyed the balance of ecosystem. Due to the advantages of convenience, simplification and economization, chemical insecticides was widely used and regarded as an important means of pest management at present when environment protection was stressed deeply. It was significant to harmonize chemical management and bio-control for the function of natural enemies. This paper was divided into three parts: Part I dealed with the toxicity of 5 insecticides, that is fipronil, chlorpyrifos, abamectin, deltamethrin and methamidophos, to 3 spiders; Part II contained mortality of 5 insecticides to main predatory natural enemies; In part III we had discussed the effects of community diversity in this different insecticides. The results were summarized as follows:1. The toxicity of 5 insecticides to Pardosa Pseudaannulata,Coleosoma octomaculatum and Tetragnatha japonica were tested in laboratory. The order of toxicity is: deltamethrin> chlorpyrifos> methamidophos> fipronil> abamectin. Concerned with the practical dosage in rice fields, the safety of 5 insecticides to three kinds of spiders was evaluated as follows: 2% abamectin EC >5% fipronil SC >50% methamidophos EC>2.5% deltamethrin EC >48% chlorpyrifos EC.2. The mortality of 5 insecticides to main predatory natural enemies might categorize three significant difference levels, among which the mortality of 48% chlorpyrifos EC, 2.5% deltamethrin EC and 50% methamidophos EC were most great, and their dosage per 666.7 square meter are respectively 60 ml,30 ml and 100ml.On the contrary, 2% abamectin EC were least with 20 ml. With dosage increased, the mortality of fipronil went up, and which was similar with that of 2% abamectin EC under lower-dose such as 20 ml and 30 ml. At seedling stage the mortality of these insecticides to spiders and Microvella dauglasi Scott conformed to field condition.3. Based on preliminary investigation in fixed position in Xiangyin, 41 species 13 families of spider and 26 species of insect natural enemy were found in the community of predatory natural enemies of single-cropping paddy fields. The...