Effects Of Several Pesticides On Flight Capacity, Energy Substances And Reproduction Of The Brown Planthopper,Nilaparvata Lugens(Stal)(Hemiptera:Delphacidae)

The brown planthopper (BPH), Nilaparvata lugens(Stal)(Hemiptera:Delphacidae), is a long-distance migratory insect pest in temperate eastern Asia and a typical recurrent pest induced by pesticides. However, the effects of insecticides on the flight capacity and the effects of fungicide jinggangmycin on the reproduction of BPH have not been investigated. The present study examined changes in the flight capacity, the energy substance, and the fecundity of BPH under the stress of several pesticides. The results are showed as follows:1Insecticide-induced enhancement of flight capacity of the BPHTo understand the mechanisms of migration and resurgence of BPH induced by insecticides, we investigated the effect of insecticides on the flight capacity on this species. An automated flight-mill system was used to assess the flight capacity of adults reared on untreated and insecticide treated plants. In most instances, the flight duration of adult females exposed to high concentrations of imidacloprid, triazophos or deltamethrin was significantly greater than that of untreated controls.Compared to the controls, the flight duration of females increased by140%(from103to245.9min),119%(from103to226min) and78%(from103to183.3min) with10mg/L imidacloprid,40mg/L triazophos and3mg/L deltamethrin, respectively, yet no significant difference in the flight duration of males was found between the insecticide treatments and the controls. The high concentrations of the three insecticides significantly enhanced the flight speed and the flight distance of both males and females, with the exception of the flight speed of adult males treated with deltamethrin. For example, the flight speed of adult females and males treated with10mg/L imidacloprid,40mg/L triazophos and6mg/L deltamethrin increased by75%(from0.39to0.68km/h),154%(from0.39to0.98km/h) and124%(from0.39to0.87km/h) for females and by141%(from0.32to0.77km/h),73%(from0.32to0.55km/h) and48%(from 0.32to0.47km/h) for males, respectively, compared to the controls. In addition, the percentages of individuals treated with imidacloprid and triazophos flying for over60min doubled compared to the control. These findings are relevant for understanding the migration and outbreak patterns of BPH.2Effects of three insecticides on content of trehalose and on trehalase activity of BPHTo understand physiological mechanism of insecticide-induced enhancement of flight capacity of BPH, the present investigation examined the changes of trehalose content and the trehalase activity of the3rd and5th instar nymph and the adults of BPH under the stress of three insecticides. The results showed that there were no significant differences on the content of trehalose and the trehalase activity in3th instar nymphs treated with three insecticides compared to the control. The content of trehalose in5th instar nymphs treated with40mg/L triazophos was significantly lower than that in the control, decreasing by24%. However the trehalase activity in5th instar nymphs treated with20and40mg/L triazophos was significantly higher than that in the control, increasing by100%and129%, respectively. Compared to the controls, the contents of trehalose in brachypterous female and male adults were significantly reduced following10mg/L imidacloprid,20and40mg/L triazophos and3and6mg/L deltamethrin, decreasing by36%,53%,67%,58%,69%and59%,71%,65%,70%,77%, respectively. While the trehalase activity in brachypterous female and male adults were significantly increased following40mg/L triazophos and3and6mg/L deltamethrin, compared to the controls, increasing by124%,100%,88%and146%,132%,118%, respectively. The contents of trehalose in macropterous female and male adults treated with10mg/L imidacloprid,40mg/L triazophos and3mg/L deltamethrin were significantly lower than that in the control, decreasing by44%,34%,37%and48%,54%,43%, respectively. While the trehalase activity in macropterous female and male adults treated with5and10mg/L imidacloprid was significantly higher than that in the control, increasing by170%,97%and317%,300%.3Fungicide jinggangmycin-induced the stimulation of the fecundity of BPHJinggangmycin is an antibiotic fungicide against rice sheath blight, Rhizoctonia solani, in China. It has been overused because of its very low toxicity to mammals and very cheap price. Therefore, the side effect of jinggangmycin is very easily neglected, which may result in resurgence of non-target pests. The previous investigation showed that jinggangmycin foliar spray stimulated the fecundity of BPH, but effects of different application methods and concentrations of jinggangmycin on the reproduction of BPH have not been investigated. Here, we investigated three application methods (foliar and stem sprays and topical treatment) and four concentrations (100,200,400and800mg/L) of jinggangmycin on the reproduction of adult females. The results showed that foliar spray significantly stimulated the fecundity of BPH and increased the number of egg-laying, vitellin content in female ovaries and the gene expression level of vitellogenin (Nlvg), but no significant effect on the reproduction was found for stem spray. In four concentrations of jinggangmycin,100,200and400mg/L foliar sprays and100and200mg/L topical treatments significantly increased the number of egg-laying, vitellin content and the gene expression level of Nlvg compared to control. Therefore, we suggest that stem spray at over400mg/L should be applied when jinggangmycin is used in against rice sheath blight to harmonious control of rice pests.