Detecting the presence of target-site resistance to neonicotinoids and pyrethroids in Italian populations of Myzus persicae.

BACKGROUND: Myzus persicae is a key pest of peach, which in commercial orchards is mainly controlled by chemical treatments. Neonicotinoids represent the main control strategy, but resistance monitoring programmes in Southern Europe have shown the widespread presence of populations highly resistant to this insecticide class in peach orchards. Moreover, in Italy reports of neonicotinoid application failures are increasing. This work describes the status of the main target-site mutations associated with neonicotinoid and pyrethroid resistance in Italian populations collected in 2012.
RESULTS: R81T mutation linked with neonicotinoid resistance was found in 65% of analysed aphids (35.5% with a homozygous resistant genotype). For the first time, R81T was found in samples collected from herbaceous hosts. Bioassays on a few genotyped populations also revealed the involvement of P450-based metabolic resistance. Only a few individuals without kdr (L1014F) and s-kdr (M918T) target-site mutations were collected. A new single nucleotide polymorphism in the s-kdr locus producing M918L substitution was found.
CONCLUSION: Target-site resistance to neonicotinoids is common in specialised peach-growing areas, and it is spreading in other Italian regions and on herbaceous hosts. The high frequency of target-site mutations and data obtained from bioassays confirm the presence of multiple resistance mechanisms and suggest the importance of coordinated control strategies.