Resistance Monitoring Of Helicoverpa Armigera In Hebei Province, Resistance Risk Assessment To Chlorantraniliprole Of Helicoverpa Armigera

Helicoverpa armigera （Hübner） belongs to Lepidoptera, Noctuidae, which is aworldwide important agricultural pest. H. armigera outbroke and caused significanteconomic losses in1990s. In order to integrated control H. armigera, the transgenic Btcotton was promoted in Hebei province in1998. Now, in order to knowledge the resistancelevel of H. armigera to insecticides after transgenic Bt cotton were cultivated in Hebeiprovince, resistance and its mechanism were studied in laboratory. The chlorantraniliproleis a new kind of pesticide, which was widely applied on the cotton in the last five years inChina. To evaluate the resistance risk of H. armigera to chlorantraniliprole, the resistanceselection, resistance heritability of H. armigera to chlorantraniliprole was conducted. Theresults are as follows:1. Resistance to insecicides were determined in three populations of H.armigera,collected from southern suburbs of Baoding, Nanpi county of Cangzhou andJulu county of Xingtai in transgenic Bt cotton field. The results showed that the LD₅₀valueto phoxim was0.7166⁰.7166μg/larva in three populations, resisitance level decreasedcompared with the LD₅₀value0.9795¹.0833μg/larva in1997. The LD₅₀value tomethomyl was0.3322⁰.6277μg/larva in three populations, resisitance level decreasedcompared to the LD₅₀value0.3908¹.6768μg/larva in1997. The LD₅₀value tolambda-cyhalothrin was0.1152⁰.4512μg/larva in three populations，resisitance levelincreased compared to the LD₅₀value0.0388⁰.0534μg/larva in1997. The fieldpopulations of H. armigera were susceptible level to organophosphorus insecticides（malathion and chlorpyrifos）, middle or high resistence level to pyrethroid insecticides（beta-cypermethrin and fenvalerate）, susceptible level to chlorantraniliprole. Therefore,organophosphorus, methomyl and chlorantraniliprole pesticides should be used in cottonand corn crop in Hebei province, pyrethroid insecticides should be used as less as possible.2. The resistence mechanism of H. armigera was studied. The results indicated thatglutathione S-transferase （GSTs） and acetylcholinesterase （AChE） activity increased to1.20¹.63times and1.15¹.23times respectively in the three field populations comparedwith susceptible population. The carboxylesterase （CarE） activiy in populations ofsouthern suburbs of Baoding, Nanpi increased to1.23and1.15times respectivelycompared with susceptible population. The results demonstrated that the resistance of H.armigera to insecticides may be correlated with increased activity of CarE, AChE and GSTs.3. F₁₅with resistance ratio of13.00had been screened13times by chlorantraniliprolein laboratory. Realized heritability （h²） of resistance in selection stages was evaluatedbased on the Tabashnik’s methods. The results showed that h²for the entire selectionexperiment was0.1495. To predict the development of resistance, it required1.87¹2.23generations of H. armigera to obtain10-fold increase of chlorantraniliprole under selectionpressure at50⁹0%mortality for each generation of selection. The results showed that H.armigera had high capability of developing resistance to chlorantraniliprole.4. The activities of enzymes were analyzed in F₀、F₅、F₁₁and F₁₅generations. TheCarE and GSTs and AChE activities of F₁₅increased by1.54,1.13and1.11foldscompared with F₀,respectively. The results showed that the resistance of H. armigera tochlorantraniliprole may be correlated with increased activity of CarE, AChE and GSTs.5. The biological characteristics were analyzed in F₀、F₅、F₁₁and F₁₅. The resultsshowed that there were significant differences in larval duration、pupation rate andemergence rate between F₁₅and F₀. The larval duration of F₁₅delayed1.40d comparedwith F₀. The pupation rate and emergence rate were reduced4.43%and5.63%,respectively. There were no significant differences in pupal duration, number of eggs laidper female, adult longevity, sex ratio and pupal weight of F₁₅compared with F₀.