Geographic variability in response to azinphos-methyl in field-collected populations of Cydia pomonella (Lepidoptera: Tortricidae) from Argentina

Insecticide resistance in the Cydia pomonella (L): Global status, mechanisms, and research directions

The codling moth, Cydia pomonella (Lepidoptera: Tortricidae) is a major pest of pome fruit and walnuts worldwide. Although environmentally compatible integrated control strategies, such as mating disruption, attract-kill strategy, and sterile insect technique have been conducted for management of this notorious pest, effects to control of codling moth have mainly relied on insecticides. In consequence, different levels of insecticide resistance towards organophosphates, neonicotinoids, hydrazines, benzoylureas, pyrethroids, diamides, spinosyns, avermectins, JH mimics, carbamates, oxadiazines and C. pomonella granulovirus (CpGVs) have developed in codling moth in different countries and areas. Both metabolic and target-site mechanisms conferring resistance have been revealed in the codling moth. In this review, we summarize the current global status of insecticide resistance, the biochemical and molecular mechanisms involved, and the implications for resistance management.

Occurrence of pyrethroid resistance mutation in Cydia pomonella (Lepidoptera: Tortricidae) throughout Argentina

Pyrethroid insecticides were intensively used against Cydia pomonella in the Río Negro and Neuquén valley, main production area of pome fruits in Argentina. Therefore, the first objective was to evaluate lambda-cyhalothrin resistance levels in C. pomonella larvae from orchards in this area that are currently under pyrethroids treatments. The second objective was to evaluate the frequency of kdr mutation in C. pomonella across Argentina. High levels of resistance to lambda-cyhalothrin (resistance ratios > 30) were determined in all the populations evaluated. The L1014F (kdr) mutation was evaluated in 355 diapausing larvae collected in 12 orchards from San Juan to Santa Cruz provinces (1690 km away from each other). The highest frequency of kdr mutation was determined in larvae from the Río Negro and Neuquén valley (0.61), followed by those from Mendoza (0.36). The kdr allele was absent or present at very low frequencies in orchards subjected to low pyrethroid pressure. The frequency of detection of kdr mutation in C. pomonella from Argentina is related to the use of pyrethroids against this pest in different areas. Target-site insensitivity is, at least, one of the mechanisms involved in resistance to lambda-cyhalothrin in codling moth from the Río Negro and Neuquén valley.

Monitoring resistance of Cydia pomonella (L.) Spanish field populations to new chemical insecticides and the mechanisms involved

BACKGROUND

Widespread resistance of Cydia pomonella to organophosphates was demonstrated in populations from the Spanish Ebro Valley area which showed high levels of enzymatic detoxification. To determine the efficacy of new insecticides, neonate larval bioassays were carried out on 20 field codling moth populations collected from three different Spanish apple production areas. Synergist bioassays were performed to determine the enzymatic mechanisms involved.

RESULTS

The least active ingredients were methoxyfenozide, with 100% of the populations showing significantly lower mortality than the susceptible strain, and lambda-cyhalothrin, with very high resistance ratios (872.0 for the most resistant field population). Approximately 50% of the populations were resistant or tolerant to thiacloprid. By contrast, tebufenozide was very effective in all the field populations, as was chlorpyrifos-ethyl despite its widespread use during the last few years. Indoxacarb, spinosad and chlorantraniliprole also provided high efficacy, as did emamectin and spinetoram, which are not yet registered in Spain.

CONCLUSION

The resistant Spanish codling moth populations can be controlled using new reduced-risk insecticides. The use of synergists showed the importance of the concentration applied and the difficulty of interpreting results in field populations that show multiple resistance to different active ingredients. © 2017 Society of Chemical Industry.

Effects of chlorpyrifos on enzymatic systems of Cydia pomonella (Lepidoptera: Tortricidae) adults

The control program of codling moth (Cydia pomonella L.) in the Río Negro and Neuquén Valley is intended to neonate larvae. However, adults may be subjected to sublethal pesticide concentrations generating stress which might enhance both mutation rates and activity of the detoxification system. This study assessed the exposure effects of chlorpyrifos on target enzyme and, both detoxifying and antioxidant systems of surviving adults from both a laboratory susceptible strain (LSS) and a field population (FP). The results showed that the FP was as susceptible to chlorpyrifos as the LSS and, both exhibited a similar chlorpyrifos-inhibitory concentration 50 (IC₅₀ ) of acetylcholinesterase (AChE). The FP displayed higher carboxylesterase (CarE) and 7-ethoxycoumarine O-deethylase (ECOD) activities than LSS. Both LSS and FP showed an increase on CarE activity after the exposure to low-chlorpyrifos concentrations, followed by enzyme inhibition at higher concentrations. There were no significant differences neither in the activities of glutathione S-transferases (GST), catalase (CAT) and superoxide dismutase (SOD) nor in the reduced glutathione (GSH) content between LSS and FP. Moreover, these enzymes were unaffected by chlorpyrifos. In conclusion, control adults from the FP exhibited higher CarE and ECOD activities than control adults from the LSS. AChE and CarE activities were the most affected by chlorpyrifos. Control strategies used for C. pomonella, such as rotations of insecticides with different modes of action, will probably delay the evolution of insecticide resistance in FPs from the study area.

Captures of MFO-resistant Cydia pomonella adults as affected by lure, crop management system and flight

The main resistance mechanism of codling moth (Cydia pomonella) in the tree fruit area of Lleida (NE Spain) is multifunction oxidases (MFO). We studied the frequency of MFO-resistant adults captured by different lures, with and without pear ester, and flights in orchards under different crop management systems. The factor year affected codling moth MFO-resistance level, particularly in the untreated orchards, highlighting the great influence of codling moth migration on the spread of resistance in field populations. Chemical treatments and adult flight were also very important but mating disruption technique showed no influence. The second adult flight showed the highest frequency, followed by the first flight and the third flight. In untreated orchards, there were no significant differences in the frequency of MFO-resistant individuals attracted by Combo and BioLure. Red septa lures baited with pear ester (DA) captured sufficient insects only in the first generation of 2010, obtaining a significantly lower proportion of MFO-resistant adults than Combo and BioLure. In the chemically treated orchards, in 2009 BioLure caught a significantly lower proportion of MFO-resistant adults than Combo during the first and third flight, and also than DA during the first flight. No significant differences were found between the lures or flights in 2010. These results cannot support the idea of a higher attractiveness of the pear ester for MFO-resistant adults in the field but do suggest a high influence of the response to the attractant depending on the management of the orchard, particularly with regard to the use of chemical insecticides.

Effectiveness of 12 Insecticides to a Laboratory Population of Cydia pomonella (Lepidoptera: Tortricidae) Newly Established in China

The codling moth Cydia pomonella (L.) is an economically important fruit pest that has spread rapidly from its original site in Xinjiang to other northwestern regions of China. Insecticides are widely used to control this pest but its invasion has never been completely stopped. The aim of this study was to establish a laboratory population of the codling moth occurring in China, to investigate the effectiveness of 12 conventional insecticides to this laboratory population, and to recommend the discriminating doses for use in resistance monitoring. The laboratory population was generally similar to other laboratory strains although parameters such as survival rate and larval duration were low when compared with field populations. Toxicity varied among the insecticides tested with LC50 values ranging from 0.016 mg/l for emamectin benzoate to 55.77 mg/l for chlorbenzuron. Discriminating dose levels were determined from dose-mortality reference curves for the detection of resistance in field populations. Effectiveness of 12 insecticides to a laboratory population of codling moth in China was evaluated for the first time. This can be integrated into resistance management strategies, especially in orchards with a history of frequent insecticides applications, in order to monitor or decrease insecticide resistance in the future.

Organophosphate Resistance and its Main Mechanism in Populations of Codling Moth (Lepidoptera: Tortricidae) from Central Chile

The codling moth, Cydia pomonella (L.), is the key pest of apple production worldwide. Insecticide resistance has been reported in all producing countries, based on five different mechanisms. Codling moth in Chile has resistance to azinphos-methyl and tebufenozide in post-diapausing larvae. However, there are no studies about the susceptibility of these populations to insecticides from other chemical groups. Therefore, the efficacy of azinphos-methyl, chlorpyrifos-ethyl, esfenvalerate, methoxyfenozide, tebufenozide, and thiacloprid on neonate and post-diapausing larvae from six field populations was investigated, and identified resistance mechanisms in this species were evaluated. Neonate larvae were susceptible to all insecticides studied, but post-diapausing larvae from four populations were resistant to chlorpyrifos, one of them was also resistant to azinphos-methyl, and another one was resistant to tebufenozide. The acetylcholinesterase insensitivity mutation was not detected, and the sodium channel knockdown resistance mutation was present in a low frequency in one population. Detoxifying enzymatic activity of glutathione S-transferases, esterases, and cytochrome P-450 monooxygenases in adults differed among populations, but chlorpyrifos resistance was associated only with a decreased esterase activity as shown by a significant negative correlation between chlorpyrifos mortality and esterase activity.

The Toxicology and Biochemical Characterization of Cantharidin on Cydia pomonella

Cantharidin, a natural toxin produced by beetles in the families Meloidae and Oedemeridae, reported to be toxic to some pests, is being developed as a biopesticide in China. This study evaluates the toxicity and biochemical characterization of cantharidin on the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), an economically important fruit pest, under both laboratory and field conditions. Laboratory dose response bioassays showed that the LC50 value of cantharidin against neonate larvae was 0.057 mg ml(-1). Exposure of the larvae to 0.024 and 0.057 mg ml(-1) of cantharidin resulted in significant reduction in larval body weight. Neonate larvae exposed to LC10 of cantharidin showed increased glutathione S-transferase activity and significantly reduced the carboxylesterase and cytochrome P450-dependent mixed-function oxidase activities. Results also showed 16 and 25% ovicidal activity at concentrations of 0.057 and 0.14 mg ml(-1) of cantharidin, respectively. Field trials demonstrated cantharidin has a significant effect on both the first and second generations of C. pomonella larvae, but it exhibits a lower control efficiency than the chemical reference emamectin benzoate. Cantharidin may be considered a valuable tool for the control of codling moth.

Molecular cloning and expression of CYP9A61: a chlorpyrifos-ethyl and lambda-cyhalothrin-inducible cytochrome P450 cDNA from Cydia pomonella

Cytochrome P450 monooxygenases (CYPs or P450s) play paramount roles in detoxification of insecticides in a number of insect pests. However, little is known about the roles of P450s and their responses to insecticide exposure in the codling moth Cydia pomonella (L.), an economically important fruit pest. Here we report the characterization and expression analysis of the first P450 gene, designated as CYP9A61, from this pest. The full-length cDNA sequence of CYP9A61 is 2071 bp long and its open reading frame (ORF) encodes 538 amino acids. Sequence analysis shows that CYP9A61 shares 51%-60% identity with other known CYP9s and contains the highly conserved substrate recognition site SRS1, SRS4 and SRS5. Quantitative real-time PCR showed that CYP9A61 were 67-fold higher in the fifth instar larvae than in the first instar, and more abundant in the silk gland and fat body than other tissues. Exposure of the 3rd instar larvae to 12.5 mg L(-1) of chlorpyrifos-ethyl for 60 h and 0.19 mg L(-1) of lambda-cyhalothrin for 36 h resulted in 2.20- and 3.47-fold induction of CYP9A61, respectively. Exposure of the 3rd instar larvae to these two insecticides also significantly enhanced the total P450 activity. The results suggested that CYP9A61 is an insecticide-detoxifying P450.