Main Pests Control Effect And Pesticide Residual Research During Seedling Stage Of Spring-sowing Rape

Rape is the most important economic crop in Gansu, and often attacked by many pests. This research expected to use middle and low toxic pesticides as substitute for high toxic organophosphorus pesticides. 5 low toxic pesticides were choosed to control of primary pests ((Psylliodes punctifrons Baly), (Ceutorrhynchus asper Roel)) and were compared with phorate treatments during the seedling stage (cotyledon-7leaf).The differences were compared between 6 pesticides and three methods (seed dressing, seed dressing + spraying, spraying).The correlation were analyzed between control effect and yield in double-low rape field in Kangle County, Linxia prefecture, Gansu Province in 2009, and then the suitable pesticides and their methods were picked out.The maximum residue limit in double-low spring-sowing rape and several advices of using pesticides were proposed, in order to provide technical and theoretical support.1 The main pests control test during seedling in the spring-sowing rape field1.1 The control effect to Psylliodes punctifrons BalyThe results of comparison of damage index in different treatments showed that: among the test of seed dressing, chlorpyrifos (2~3 leaf stage 4.15%, 4~5 leaf stage 20.38%, 5~6 leaf stage 32.08%) had the lowest damage index, while fenvalerate - malathion, emamectin benzoate-chlorfenapyr took the second place. Among the test of seed dressing + spraying , fenvalerate–malathion (1.83%,15.84%,25.16%), emamectin benzoate-chlorfenapyr (6.20%,29.25%,29.24%) had the best effects, while imidacloprid took the second place. Among the test of spraying, fenvalerate– malathion (5.24%, 18.79%, 29.17%) was the best, while emamectin benzoate -chlorfenapyr, imidacloprid took the second place. Fenvalerate -malathion, phoxim, chlorpyrifos, emamectin benzoate-chlorfenapyr in the test of seed dressing and seed dressing + spraying and emamectin benzoate-chlorfenapyr in test of spraying controlled the final dead seedling rate in the range of 5%, and the damage index was controlled in the range of 40% in the field experimental demonstration, which controlled the damage to rape effectively. So chlorpyrifos, fenvalerate -malathion, emamectin benzoate -chlorfenapyr, imidacloprid would be used instead of phorate.1.2 The control effect to Ceutorrhynchus asper RoelForm dead seedling rate perspective, there was significant difference between different pesticides. Phoxim, emamectin benzoate–chlorfenapyr were the best in the seed dressing test, and phoxim, fenvalerate–malathion were the best in the seed dressing + spraying test. What'more, in the spraying test there was significant difference between the fenvalerate–malathion and Phoxim.But there was no significant difference between other pesticides. Spraying was the most suitable method to control of Ceutorrhynchus asper Roel.1.3 Comparision of the yield between different treatmentsAmong the test of seed dressing, chlorpyrifos and phorate had the higher yield than the others, but there was no significant difference between them. Among the test of dressing+spraying, the yield of fenvalerate–malathion reached 586.8g /m2 and it was the highest. Among the test of spraying, imidacloprid and emamectin benzoate -chlorfenapyr were the treatments with higher yield.1.4 Relationship between control effect and yieldThe relation analysis showed that the damage index was significantly negatively related to yield.The relative coefficient (r) between the final damage index (5-6 leaf) of spring-sowing rape and their yield was 0.4424,r>r0.01,so the damage index was very significantly negatively related to yield. The dead seedling rate was very significantly related to yield. The relative coefficient (r) was 0.5352.The damage rate was very significantly related to yield. The relative coefficient (r) was 0.4424.2 Pesticides residual detectionThe chromatography detection results in this research showed that the pesticide residual was beyond 0.010 mg/kg in rapeseed samples dressed by phorate, while residual in the others samples (0.0083 mg/kg) were below than phorate.From all above we could conclude that 5 kinds of pesticide should be choosed in this research as substitute for high toxic organophosphorus pesticides used for ages, in order to ensure the security product and quality.