Preliminary Study On Monitoring And Mechanisms Of Insecticide Resistance Of Field Population Of Diamondback Moth, Pluella Xylostella (L.)

The diamondback moth (DBM, Plutella xylostella L.) is one of the most damaging pest ofcruciferous vegetables, is also one of the pest difficult to control because of the seriousinsecticides-resistance. To clear the level of pesticide-resistance to commonly pesticides of DBMpopulation in Tonghai county of Yunnan province, the experiments by leaf immersion method was donefor3consecutive years from2011-2013. The TPP, PBO and DEM synergistic agent tests and activitydetermination of detoxification enzymes were conducted in labortary to modify the mechanism tocommonly pesticides of the field population of DBM; and the control effectives of the insecticides weretested in field experiments to DBM population in Tonghai. The research results can provide importantscientific basis for the development of scientific and reasonable resistance management strategy,improve the effect of comprehensive prevention and control, and prolong the using year of newinsecticide. The main results of research as follows:1.Using situation of insecticides controlling diamondback moth in TonghaiThere were34insecticides for controling the diamondback moth in Tonghai vegetable plantingareas. Abamectin and its derivatives (emamectin benzoate) were the main used, but had poor effect.Chlorantraniliprole as a newly developed insecticide was the best effective and used most consumable.Farmers were used to two agents mixed,5-10days spraying once at the DBM peak season in Tonghai.2. Resistance results of diamondback moth from field population to nine insecticides during2011to2013During2011to2013, a total of9kinds insecticides, including diafenthiuron, Bt, indoxacarb,chlorfluazuron, chlorfenapyr, pleocidin, chlorantraniliprole, effectiv-cypermethrin, abamectin, wereconducted their insecticide-resistance to DBM population in Tonghai county. The results showed thatthe sensibility of DBM to diafenthiuron and Bt were the highest, the LC50reduced year by year. TheLC50of diafenthiuron was between36.15to145.65mg· L-1, and Bt LC50was from0.74to1.59mg· L-1; the sensibility of DBM to chlorfenapy, spinosad, indoxacarb, chlorfluazuron，chlorantraniliprole were reducing in the three year, and belong to the moderate-high level. But theresistance level of DBM to chlorantraniliprole was increasing. The resistence of DBM to otherinsecticides in2012and2013were significantly lower than in2011. Chlorfenapyr LC50was from9.71to25.80mg· L-1, Spinosad LC50from3.80to9.23mg·L-1, indoxacarb LC50from4.80to68.957mg· L-1, Chlorfluazuron LC50from4.91to49.27mg· L-1, chlorfluazuron LC50from4.06to10.08mg·L-1, beta-cypermethrin and abamectin LC50were from270.62to2974.67mg·L-1and from6.91to38.54mg· L-1,respectively. The rank resistance levels of DBM field populations to9kindsinsecticides in Tonghai county of Yunnan province as follows: diafenthiuron <Bt <indoxacarb <chlorfluazuron <chlorfenapyr <spinosad <chlorantraniliprole <beta-cypermethrin <abamectin.3. Controll effect of insecticides used to diamondback moth in Tonghai vegetable fieldThe control effects after4days and after7days of20%chlorantraniliprole,20%flubendiamide, and1.5%abamectin were all less than50%. The control effects after4days and after7days of15%indoxacarb,2.5%spinosad and50%diafenthiuron were over80%, the former two reagents havesignificant difference with the latter three reagents, but has no significant difference with1.5%abamectin. The control effects after7days of20%chlorantraniliprole has no significant difference withthe contrast at0.05levels, has lost the effect. The control effects after14days of50%diafenthiuron wasover80%, hold the good effectiveness. The control effects of1%emamectin benzoate and Bt not verywell, the control effect after4days were only65.9%and60.8%, respectively. The rank control effectsof nine insecticides to DBM field population were: diafenthiuron> indoxacarb> spinosad> emamectinbenzoate> Bt> chlorfenapyr> flubendiamide> abamectin> chlorantraniliprole.4. The determination of detoxifying enzyme activityEnzyme activity of GST in DBM-r was0.8times that of the enzyme activity in DBM-S,multi-function oxidase was0.75times, carboxylesterase was0.77times, no significant difference (P>0.05).This results showed that the field resistant populations of detoxifying enzymes metabolicdetoxification ability had not been obviously enhanced, detoxification enzymes may involved in themetabolic process of detoxification, andhave a role to play in the case of drug induced, but there areother reasons such as skin penetration mechanism of target site sensitivity lower.5. Synergist effects of TPP, PBO and DEMThe TPP and DEM synergist on chlorantraniliprole synergistic effect was not obvious, efficiencyratio was1.28,1.47, PBO synergist for chlorantraniliprole was more than TPP, efficiency ratio was1.94,shows that the sensitivity of the chlorine worm benzamide decline may be associated withmulti-function oxidase. PBO, the TPP and DEM three synergist for abamectin had obvious synergy,efficiency ratio was2.77,4.20, and3.53times respectively, multi-function oxidase, carboxylesteraseGSH-S-transferase involved in detoxification metabolic process of abamectin.