Survey and Molecular Diagnostics of Target Site Mutations Conferring Resistance to Insecticides in Populations of Aphis spiraecola from Greece

The spirea aphid, <i>Aphis spiraecola</i> (Hemiptera: Aphididae), is a major pest of citrus and other crops, causing feeding damage and transmitting plant viruses. Control relies mainly on insecticides, increasing the risk of resistance. We surveyed Greek populations of <i>A. spiraecola</i> (2022-2023) and developed molecular diagnostics to detect target site mutations linked to resistance against neonicotinoids, carbamates, organophosphates, pyrethroids, and spirotetramat. Seventy-two aphids were analyzed. All individuals were homozygous and susceptible at R81T, A302S, L1014F, M918 variants, and A2226V loci. However, the S431F mutation in the <i>AChE2</i> gene, associated with resistance to dimethyl-carbamates, such as the selective aphicide pirimicarb, was present in all regions. Heterozygotes occurred at high frequencies, while homozygous resistant individuals were rare. These findings indicate that Greek populations remain largely susceptible to most insecticide classes, but the widespread occurrence of S431F questions the use of pirimicarb in resistance management. The diagnostic assays developed here are cost-effective tools for large-scale monitoring, enabling early detection of resistance in <i>A. spiraecola</i>. Continued surveillance, combined with bioassays and studies on metabolic mechanisms, will be essential for sustainable pest management.