Double Effects Of Azadirachtin And Its Compound On Rice Stem Borers And Growth Of Rice

The control effect of biogenic pesticides especial azadirachtin and its compound against rice stem borers were compared during 2002-2004 at Yangzhou, Jiangsu province. The double effect of azadirachtin on stem borers and growth of rice were studied under different dosage and different stages. Its functional pattern on stem borers was discussed. The main results were as following:1. The mortalities of two kinds of stem borers (scirpophageincertulas and cnaphalocrocis medinalis) were different with biogenic pesticides, including azadirachtin, avermectins, Bt, Baibu, and chemical pesticide triazophoes, their compounds. Among all biogenic pesticides, azadirachtin and avermectins had best effect on controlling scirpophageincertulas and cnaphalocrocis medinalis. The mortality of scirpophageincertulas and cnaphalocrocis treated with azadirachtin were 72.2% and 85.7%, respectively, and the mortalities with avermectins were 66.0% and 80.1%, respectively. The control effects of azadirachtin and avermectins were as same as that of triazophoes. Biogenic pesticides including BT and Baibu were not suitable in crop protection. Among pure biogenic pesticides, compound, mixed with azadirachtin and avermectins had better effect, and among pesticides with half biogenic and half chemical, the compound mixture alian or lianzuo with triazophoes had better effect.2. The azadirachtin and its compound had remarkable different control effect against stem borers with dosages at different stages. The suitable stage for chilosuppressalis was before 2-3 days of egg-hatching time, and the suitable dosage was 100ml/mu, and the morality of chilosuppressalis was 91.43%. The control effects of azadirachtin and itscompound--alian and lianzuo varied on scirpophageincertulas and cnaphalocrocismedinali showed efficiency at booting time> at early heading time> at heading time.The suitable dosage of azadirachtin, alian and lianzuo were 100ml/mu,100ml/mu and 125ml/mu (2: 3) , respectively. Their effects were as high aslOOml/mu of triazophoes. 3 The azadirachtin had many functional patterns for chilo suppressalis as antifeedant, growth regulation deterrent, oviposition and others, being treated with 0.75×10-3, 0.5×10-3, 0.375×10-3, 0.3×10-3 and 0.25×10-3ml/L azadirachtin, the antifeedant rates were 70.82%, 65.74%, 58.64%, 36.69% and 23.61% .respectively. The 3th-instar larvae completely died in 6 days, 12 days respectively after being fed on seeding treated with 0.75×10-3ml/L and 0.5×10-3ml/L azadirachtin. The larvae growth was obviously retarded being fed on seeding treated with 0.375×10-3 ml/L, 0.3×10-3 ml/L and 0.25×10-3ml/L azadirachtin respectively. The oviposition deterrence rate was 88.60% after fed on seeding treated with 10×l0-3 ml/L azadirachtin.4. The yield was significantly increased by azadirachtin and its compound alian. Chlorophyll content, rooting, biomass were promoted by azadirachtin and alian at seeding stage, and the seeding was boosted. When rice transplanted by root-soaking method, the leave and tillers could be boosted, and the yield was raised. When azadirachtin was sprayed at end-booting time on paddy, not only damage of stem borers could was controlled, and yield loss be reduced, but also the quantity of chlorophyll was increased, the death of leaves were delayed, grain filling was promoted and the set rat and yield were raised remarkably.