Rapid recovery of susceptibility under harsh environmental conditions in fenvalerate-resistant strains of the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract

Resistance to fenvalerate was examined in a laboratory-selected population of the diamondback moth, Plutella xylostella, during exposure through 10 generations. Selection results showed that LD 50 values rose from 0.003 mg per larva to 31.1 mg per larva and 36.7 mg per larva respectively, in replications 1 and 2 during those 10 generations. Resistant line moth eggs were significantly smaller than those of moths before selection. Therefore, we selected a subpopulation of resistant lines under harsh environmental conditions of low humidity and high temperature, over 10 generations (Harsh line) without insecticide exposure. We selected another subpopulation of resistant lines under optimal environmental conditions of high humidity and normal temperature through all 10 generations (Optimal line). After 10 generations, the LD 50 of fenvalerate decreased to 0.03 mg per larva and 0.02 mg per larva under harsh conditions and 0.2 mg per larva and 0.29 mg per larva under optimal conditions. The LD 50 values were lower for the Harsh lines than for the Optimal lines in all generations. The egg size of both lines increased gradually through 10 generations. Comparisons of these two lines showed that the egg size increased more rapidly in the Harsh lines than in Optimal lines in early (first-sixth) generations. In subsequent generations, egg sizes were nearly normal in both lines. Comparison of immature survivability of Harsh and Optimal lines reared under those conditions showed that the survivability of Harsh line individuals was significantly lower than for Optimal lines. Comparison of the two lines' survivability showed an opposite result from the comparison when they were reared under equivalent optimal conditions. These results suggest that susceptibility to insecticides might recover more quickly in Harsh lines than in Optimal lines because resistant insects with small eggs had lower survivability than susceptible insects with normal eggs. They were eliminated more rapidly under harsh environmental conditions.

Resistance to commonly used insecticides in Asian citrus psyllid: Stability and relationship to gene expression

“…The decline in resistance in the field population indicates that if the insecticides implicated in resistance are removed from the spray schedule, reversion to susceptibility should be observable fairly rapidly in the field as was documented for D. citri previously (Coy, Liu, & Stelinski, ). Given the likelihood of fitness cost, it is possible that reduced insecticide use reduced the selection of resistant individuals and susceptibility among D. citri populations increased (Chen et al., ; Coy et al., ; Georghiou, ).…”

“…In the present study, resistance to imidacloprid and thiamethoxam was unstable in field populations of D. citri in Florida in the absence of insecticide exposure under laboratory conditions. Unstable insecticide resistance has also been reported in the diamondback moth, Plutella xylostella (Linnaeus) (Chen, Sanada-Morimura, Yanagi, & Nakasuji, 2006); silverleaf whitefly, B. tabaci (Basit et al, 2011;Chen & Nakasuji, 2004); housefly, Musca domestica L (Keiding, 1953); red mite, Panonychus citri (McG.) (Inoue, 1979); and green peach aphid, Myzus persicae Sulz (Needham & Sawicki, 1971).…”

Insecticide toxicity associated with detoxification enzymes and genes related to transcription of cuticular melanization among color morphs of Asian citrus psyllid

“…For example, orange morphs of M. persica are less susceptible to insecticides than red and green morphs (Srigiriraju et al ., ). Second, increasing metabolic detoxification of toxicant target sites is a mechanism of resistance development (Brattsten et al ., ; Chen et al ., ). Esterases are frequently implicated in detoxification of organophosphates, carbamates, and pyrethroids by insects (Hemingway & Ranson, ; Srigriraju et al ., ).…”

“…Estimation of defense-related detoxifying enzyme activity may provide information regarding the degree of tolerance that insect pest populations may exhibit to insecticides and may be useful tools for monitoring pest susceptibility to insecticides. It has been well established that detoxification enzymes play a substantial role in development of resistance; however, insect toxicity to insecticides can also evolve due to reduced penetration of toxicants, alterations of target sites, and behavioral modifications (Brattsten et al, 1986;Chen & Nakasuji, 2004;Chen et al, 2006). Bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), have reemerged as a major household pest within the USA.…”

Temperature, deltamethrin‐resistance status and performance measures of Plutella xylostella: complex responses of insects to environmental variables

“…When considering other parameters, a DBM line resistant to fenvalerate had significantly smaller eggs and a lower survival rate than the susceptible line (Chen et al, 2006a). The fenvalerate-resistant and susceptible lines were exposed to unfavourable dry and hot environments without selection pressure of fenvalerate in their subsequent study, and the resistant line showed higher mortality and its susceptibility to fenvalerate returned within 10 generations (Chen et al, 2006b). Similar to the present study, it also reveals that abiotic stressors could strongly direct the evolution of insecticide-resistant populations of insects.…”