Genetics and mechanism of resistance to deltamethrin in a field population of Spodoptera litura (Lepidoptera: Noctuidae)

Abstract

BACKGROUND: Spodoptera litura (F.) causes enormous losses in many economically important crops. The genetics of insecticide resistance has been extensively studied in several insect pests, but there is a lack of information on S. litura. Therefore, the genetics and mechanisms of the resistance of S. litura to deltamethrin were investigated. RESULTS: Bioassays at generation G1 gave resistance ratios of 9, 5, 41, 52 and 49 for deltamethrin, cypermethrin, profenofos, chlorpyrifos and triazofos respectively, when compared with the susceptible Lab‐PK strain. Bioassays at G4 with a deltamethrin‐selected population (Delta‐SEL) showed that selection gave resistance ratios of 63 and 7 for deltamethrin when compared with the Lab‐PK and UNSEL strains respectively. Cross‐resistance to other insecticides tested was observed in the selected population. A notable feature of the Delta‐SEL strain was that resistance to deltamethrin, cypermethrin, profenofos and chlorpyrifos did not decline over the course of five generations. Synergism tests with microsomal oxidase (MO) and esterase‐specific inhibitors indicated that the deltamethrin resistance was associated with MO and, possibly, esterase activity. Reciprocal crosses between the Delta‐SEL and Lab‐PK strains indicated that resistance was autosomal and incompletely dominant. A direct test of monogenic inheritance suggested that resistance to deltamethrin was controlled by more than one locus. CONCLUSION: Stability and dominance of resistance and cross‐resistance suggest that insecticides with different modes of action should be recommended to reduce pyrethroid selection pressure. Copyright © 2007 Society of Chemical Industry

Esterase-based metabolic resistance to insecticides in heliothine and spodopteran pests

“…from South Asia). 95,96,113,114) Kim et al 97) found several-fold higher in vitro esterase activities for a /b -naphthyl acetate and p-nitrophenyl acetate in some of these field-derived resistant lines. Three studies of lines selected for enhanced SP resistance in the laboratory have also shown increases in naphthyl acetate activities over the course of selection, 96,98,115) and one of these studies 115) showed relaxation of selection led to concomitant decreases in resistance and naphthyl acetate activities.…”

Field evolved resistance to carbamates, organophosphates, pyrethroids, and new chemistry insecticides in Spodoptera litura Fab. (Lepidoptera: Noctuidae)

“…Analysis of resistant populations relies on comparisons with standard susceptible laboratory population. The results of assays with Lab-PK population showed a similar response to insecticides as another laboratory population from the Pakistan (Ahmad et al 2007b). The slopes of the regression lines of all insecticides tested against the population were similar, suggesting less heterogeneity in the population.…”

“…This indicates that more than one mechanism of resistance exists for imparting resistance to the insecticides in S. litura from Pakistan. Previous studies from our laboratory on the synergism by piperonyl butoxide and DEF showed that both monoxygenases and esterases might be involved in imparting resistance to indoxacarb, pyrethroids, and emamectin in the Pakistani populations of S. litura (Ahmad et al 2007b;Shad et al 2010) or spinosad in Plutella xylostella . In contrast, toxicity to betacyfluthrin and emamectin was quite high whereas very low level of resistance for chlorpyrifos, and bifenthrin was observed.…”

“…The emerged adults were kept in glass jars that were provided with tissue papers hung vertically for oviposition. They were fed on a solution containing 10% honey soaked onto cotton wool ball (Ahmad et al 2007b). The field-collected populations were reared in the laboratory to acclimatize to laboratory conditions and to obtain sufficient insect numbers for bioassays.…”

“…A standard leaf disc bioassay method (Sayyed et al 2000;Ahmad et al 2007b) was performed for the field collected and laboratory susceptible, Lab-PK populations by using second instar larvae of S. litura. Cotton leaf disks of single variety, 4.8 cm diameter were cut, washed, dried, immersed in a test solution without surfactant for 10 s and allowed to dry at ambient temperature for 1-1.5 h. Control leaf disks were only dipped in water without any surfactant.…”