Studies On Insecticides To Main Pest Of Cruciferous Vegetables And Harmonia Axyridis

This thesis studied the key insect pest Laphygma exigua and Myzus persicae of cruciferous vegetables and their integrated management in Weifang district, Shandong province.1. Chlorfenapyr has the best control effectiveness of the 3 rd larvae of Laphygma exigua among the 7 kinds of insecticides for testing, its LC₅₀ is 0.6621mg/L. Hexaflumuron comes second, its LC50 is 0.9612mg/L. Both of them have better effectiveness than phoxim. LC₅₀ of fipronil and lambda-cyhalothrin are respectively 1.2568mg/L and 2.3996mg/L. Their effectiveness respectively are 2.9 times and 2.5 times than avermectin.2.The 7 kinds of insecticides have completely similar control effectiveness of the 1^st, 2^nd and 3^rd larvae of Laphygma exigua. Chlorfenapyr and hexaflumuron have the best effectiveness. If we use chlorfenapyr 2000 multiple slution to control the 3^rd larvae , the corrected mortality amounts to 96.5%, hexaflumuron can reach to 93.1 %, their controlling effectiveness are almost similar to phoxim. Chlorfenapyr, lambda-cyhalothrin, avermectin come second, their mortality amounts to 78%⁸9%. Tebufenozide almost has no control effectiveness.3. Chlorfenapyr is the best one on control the larvae of Laphygma exigua, its control effectiveness are respectively 96.2%, 99.1%, 96.5% after 5, 7 and 14 days when chlorfenapyr are used. Hexaflumuron and fipronil come second. Their control effectiveness are respectively 94.8%, 96.6%, 93.1% and 95.1%, 95.3%, 90.3%, their control effectiveness stably comes to above 90% between 5 and 14 days after the insecticides are used. Lambda-cyhalothrin and phoxim come second. Avermectin, tebufenozide s effectiveness are less than the others.4. Acetaniprid has the best effectiveness to countrl Myzus persicaeamong the 6 kinds of insecticides for testing. Medicine used 1.5 hours, the mortality has been reached to 89.44%, obviously better than imidacloprid and pinmicarb. Acetaniprid's control effectiveness is similar to imidacloprid after 6 hours, both of their mortality can reach to 94%. And the mortality can reach to 100% after 24 hours.The corrected mortality can reach 100%, when imidacloprid is used 12 hours later. The bioactivity and rate of controlling effect are equal to acetaniprid after 24 hours, the control effectiveness of phoximN pirimicarb -. cyhalothrin are from 84.3% to 89.6%. Acetaniprid and imidacloprid have better control effectiveness.5 Acetaniprid and imidacloprid have better control effects on Myzus persicae, the corrected mortality of both then amounts to above 90% after used 5—14 days. Acetaniprid has the best control effectiveness, its effectiveness still amounts to 98.5% even after 14 days.Pirimicarb has the best control effectiveness after 3days, which can reach to 95.6%, but its effect will decrease after that. It will decrease to 77.3% after 14 days. Cyhalothrin, phoxim s control effectiveness are the lowest, about from 76.8%to 82.6%, its using should be reduced in the production.6 The relative toxicities and safety factors of 5 kinds of insecticides (chlorplyrifos, acetaniprid, beta-cypermethrin, cyhulothrin, avermectin) on Harmonia axyridis is determined respectively in the laboratory. Beta-cypermethrin has the greastest toxicity. Cyhulothrin comes second. Chlorpyrifos's toxicity in the middle of these insecticides. Acetaniprid and avermectin's toxicities are less than any other insecticides. But the safty factors of the 5 kinds of insecticides is opposite to toxicity. The results show that pyrethroid insecticides toxicities were strong. Toxicities of op insecticides are middle. Nicotin se rize and natural products insecticides toxicities were weak. But the op insecticides are the most harmful to Harmonia axyridis in these kinds of insecticides considering from the aspect of security. Therefore, in the process of synthetic management of aphides the choice of nicotin se rizeand natural products insecticides is proper. Because it can avoid harming the natural enemies of aphides.