Age‐dependent response to insecticides and enzymatic variation in susceptible and resistant codling moth larvae

Abstract

Insecticide resistance in the codling moth, Cydia pomonella, partly results from increased metabolic detoxification. The aim of this study was to follow the age variations in larval susceptibility to deltamethrin and teflubenzuron in one susceptible (S) strain, and two resistant (Rv and Rt) ones selected for resistance to deltamethrin and diflubenzuron, respectively. The age variation of the activities of cytochrome P450-dependent monooxygenase (MFO), glutathione S-transferases (GST), and esterases in S and both resistant strains were simultaneously investigated. The highest levels of insecticide resistance were recorded in late instars in both resistant strains, although Rv neonates exhibited enhanced resistance to deltamethrin. The involvement of an additional deltamethrin-specific mechanism of resistance, which could be mainly expressed in early instars, was supported by previous demonstration of a kdr point mutation in the Rv strain. The cross-resistance between deltamethrin and teflubenzuron indicated the involvement of non-specific metabolic pathways in resistance to teflubenzuron, rather than target site modification. A positive correlation between enhanced GST activities and deltamethrin resistance suggested that this mechanism might take place into the adaptive response of C. pomonella to pyrethroids treatments. Enhanced MFO activity was recorded in each instar of the two resistant strains compared to the susceptible one. But these activities were not correlated to the responses to deltamethrin nor to teflubenzuron. In the light of these findings, studying age-dependence of responses to selection is central to the implementation of monitoring tests of resistances, especially if the target instars are difficult to collect in the field.

Insecticide resistance may enhance the response to a host-plant volatile kairomone for the codling moth, Cydia pomonella (L.)

“…Neonate progeny were selected by exposure to increasing concentrations of diflubenzuron (for the Rdfb strain) or deltamethrin (for the RΔ strain) that induced 50% mortality for the first ten generations at concentration high enough to kill all susceptible larvae for 20 following generations. At the end of this selection regime, individuals of Rdfb and RΔ strains expressed homogeneously enhanced mixed-function oxidase (mfo) and glutathione S-transferase (GST) activities (Sauphanor et al 1997;Bouvier et al 2002). In addition, individuals from the RΔ strain were homozygous for a resistance allele (kdr-type) at the sodium channel gene Brun-Barale et al 2005).…”

Evaluation of mechanisms of azinphos‐methyl resistance in the codling moth Cydia pomonella (L.)

“…Enhanced levels of activity of certain metabolic detoxifying enzyme systems such as esterases, mixed function oxidases (MFO), and glutathione S-transferase (GST) have been suggested for conferring resistance. A low activity of general esterases in adult moths resistant to parathion (Bush et al, 1993) and differences in GST and MFO activities in insects resistant to deltamethrin October 2004 and diflubenzuron (Bouvier et al, , 2002Sauphanor et al, 1997) have been reported.…”

Monooxygenase Activity in Methidathion Resistant and Susceptible Populations of Amblyseius womersleyi (Acari: Phytoseiidae)

“…The codling moth, Cydia pomonella (L.), and other insects in temperate areas enter diapause in response to short days (Steinberg et al 1992), and therefore some active life stages may not be found in the orchards during determined periods of the year. For codling moth the highest levels of deltamethrin resistance were recorded in late instars of resistant strains (Rv and Rt) of this insect, although Rv neonates exhibited enhanced resistance to deltamethrin (Bouvier et al 2002).…”