Early detection of resistance to tebufenozide in field populations of Cydia pomonella L.: methods and mechanisms

Abstract

Four populations of codling moth Cydia pomonella L. were collected as overwintering larvae from apple orchards with different pesticide pressure (S. Michele, Roncafort, Revo`and Vervo`) in the Trento province (northern Italy). Mortality rate caused by a predetermined discriminating concentration of tebufenozide topically applied on overwintering larvae was evaluated. Neonate F1 progeny of the same populations were assayed for susceptibility to tebufenozide by feeding them on thinning apples treated with an appropriate discriminating dose of the insecticide. The activities of the main enzyme systems involved in the detoxification of insecticides were also evaluated in each population and related to their susceptibility to tebufenozide. The topical test detected a significant loss in susceptibility to tebufenozide in two populations, S. Michele and Roncafort, while all the overwintering larvae collected in the orchards of Revo`and Vervo`died when treated topically with the discriminating concentration. The apple-dipping test performed on the neonate larvae showed a highly significant reduction in the susceptibility of the two populations of S. Michele and Roncafort. A less significant reduction in mortality rate was found in the Revo`population; however, no statistical difference was found between the Vervo`population and the susceptible reference. None of the four field populations significantly differed from the susceptible strain for Glutathione-S-transferase and esterase activity. A significantly higher frequency of individuals of the S. Michele and Roncafort populations exhibited a higher mixed function oxidase activity than the susceptible strain. The small resistance ratio values found for the two populations together with the low frequency of individuals exibiting enhanced enzymatic activity, reveals that the selection process was still at the early stage. Because of its efficiency in early detection of resistance to tebufenozide, topical application on diapausing larvae can thus be considered an appropriate, simple and robust tool for implementing resistance monitoring programmes for tebufenozide.

Toxicity of emamectin benzoate to Cydia pomonella (L.) and Cydia molesta (Busck) (Lepidoptera: Tortricidae): laboratory and field tests

“…The dose response laboratory bioassays showed that emamectin benzoate had a similar high level of intrinsic toxicity to early‐stage larvae of both C. pomonella and C. molesta . In a previous experiment, Ioriatti et al 5 used the same C. pomonella culture and laboratory bioassay, which resulted in LC 50 values for the MAC tebufenozide 10 times higher than those found in this study for emamectin benzoate. Moreover, emamectin benzoate has been reported to be the most active compound against Grapholitha lobarzewskii Nowicki, with an LC 50 of 0.01 mg L −1 17…”

“…The efficacy of C. pomonella control is threatened by the widespread development of resistance to pesticides 3. Resistance to different classes of insecticides has recently been documented in codling moth populations by using topical applications on overwintering larvae, a sensitive technique for detecting resistance 4, 5. According to Charmillot et al ,6, 7 the only insecticide to which resistance has not developed is emamectin benzoate, which has been shown to be highly effective in laboratory tests on populations resistant to diflubenzuron and tebufenozide.…”

Development of a rapid resistance monitoring bioassay for codling moth larvae

“…Codling moth evolved resistance to lead arsenate in the early twentieth century7 and to DDT in the early 1950s,8 and it has since developed resistance to virtually every insecticide group. On a worldwide scale, populations have developed resistance to organophosphates,9–13 to benzoylureas including diflubenzuron,14–18 to the diacylhydrazines (tebufenozide and methoxyfenozide19, 20) and to pyrethroids 17, 20, 21. The occurrence of populations resistant to insecticides shortly after their appearance on the market in both Europe3 and the United States20 suggests that cross‐resistance is a potential concern for new classes of chemistry.…”

“…Topical applications to fully developed post‐diapause larvae were used to monitor for diflubenzuron17, 18 and tebufenozide19 resistance in field populations, and diagnostic doses were proposed for a diversity of insecticides 18. This bioassay required the collection of diapausing larvae in corrugated cardboard strips placed around the tree trunk, and then exposing the larvae to cold treatment for a minimum of 3 months to complete diapause development.…”

Controle de tortricídeos em macieira com duas formulações de Bacillus thuringiensis var. Kustaki em Fraiburgo-SC

“…O uso repetitivo de inseticidas no mesmo ciclo vegetativo pode selecionar populações resistentes (SAUPHANOR et al, 1998;IORIATTI et al, 2007), comprometendo a eficiência do controle.…”