Insecticides Screening For Frankliniella Occidentalis And The Control Effects Of Predatory Mite On Frankliniella Occidentalis On Tobacco

Invasive pest Frankliniella occidentalis has caused serious harm to tobacco,flowers,vegetables and other cash crops worldwide due to its strong adaptability and wide host range.In agricultural production,the use of chemical pesticides to control F.occidentalis often leads to negative effects such as pesticide pollution,drug resistance and killing natural enemies,and cannot achieve good control effects.As an important part of the comprehensive management of F.occidentalis,biological control has the advantages of long duration,no resistance,no pollution to the environment,and has the potential for large-scale application.Neoseiulus barkeri is an important predatory natural enemy insect and plays an important role in the biological control of F.occidentalis.In this study,the toxicity of 5 insecticides to adult of F.occidentalis and the safety evaluation of N.barkeri were tested in laboratory.The control effect of the release pattern of N.barkeri on F.occidentalis in tobacco field was evaluated.The details are as follows:This study aims to screen out insecticides with good toxicity effect on F.occidentalis and high security to N.barkeri,and provide helpful reference to control F.occidentalis when combination use of insecticides and predatory mites in field.The toxicity of five insecticides to the adult of F.occidentalis was evaluated after feeding the bean pods soaked with insecticides for 48 hours.The reduction rates of adults F.occidentalis for each the five insecticides were 88.34% of spinetoram(60 g/L),85.56% of matrine,82.78% of thiamethoxam(25%),79.45% of avermectin(5%)and 50.12% of imidacloprid(70%),with control efficacy of 97.52%、94.43%、91.34%、87.43%、55.42%,respectively.These results showed two insecticides of spinetoram(60 g/L)and matrine control F.occidentalis had better efficacy to control F.occidentalis.N.barkeri were also fed on special wheat bran sprayed with each of the above insecticide.After 48 hours,the decrease rate of N.barkeri for the five insecticides was higher than that of water control with the following order of11.37% of matrine,9.71% of thiamethoxam(25%),9.15% of spinetoram(60 g/L),8.04%of imidacloprid(70%)and 4.70% of avermectin(5%).These results showed that avermectin(5%)was relatively safe to N.barkeri with the least influence on the population of N.barkeri.Therefore,spinetoram(60 g/L)and matrine can recommend to control F.occidentalis when use insecticides alone.If insecticides are mixed with predatory mites in agricultural production,the combined application of 5% abamectin and N.barkeri will better play the efficacy of insecticides and predatory mites.To explore the release way with the best control effect on F.occidentalis through spraying N.barkeri on tobacco plants and/or weeds with different times in the field.N.barkeri was sprayed one to three times with 15-day intervals,respectively,during tobacco growing season in the field.Three N.barkeri release ways including application N.barkeri on both tobacco and weeds,only on tobacco or weeds were set respectively under each release time.The control effect of N.barkeri on F.occidentalis on tobacco field was evaluated by comparing the population of F.occidentalis under different releasing times and methods.The investigation results of thrips population quantity in different experimental treatments showed,F.occidentalis population in the tobacco field was reduced at different level when N.barkeri was released by different ways.Among them,application N.barkeri three times on both tobacco and weeds reached the best control effect on the population of F.occidentalis,with the relative control effect of 58.02% and the longest duration.The control effect of twice application of the N.barkeri was the second,and the highest relative control effect was 55.57%.While the control effect on F.occidentalis was the worst after only one application of N.barkeri,and the highest relative control effect was only 49.96 % and the duration of the control effect was the shortest.At the same application time,the control effect of N.barkeri applied only to tobacco plant was slightly higher than that only to the weeds,but there was no significant difference between them.Therefore,the application of N.barkeri both on tobacco and weeds in the tobacco fields can achieve better control of F.occidentalis,and at least two applications of the N.barkeri on both tobacco and weeds in the tobacco fields with an interval about 15 days can achieve a relatively satisfied control effect.The more N.barkeri application time,the better control effect on thrips such as F.Occidentalis will be reached,as cost allows.