Putative PCR markers for insecticide resistance in the leafminer, Liriomyza trifolii (Diptera: Agromyzidae), to cyromazine and abamectin

A number of cases of insecticide resistance to cyromazine and abamectin have been reported in the leafminer, Liriomyza trifolii (Burgess), from commercial ornamental production greenhouses. Leaf dip bioassays have been used for resistance determination but results are usually not available until a month or two later, due to having to rear the leafminers through a generation or two to obtain enough healthy robust individuals for bioassay. This delay does not allow the grower to choose the most effective product to control an existing leafminer problem. In this study random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) was used to identify polymorphic genomic DNA that would discriminate among cyromazine-resistant, abamectin-resistant and susceptible leafminers. Using a reference strain, which was susceptible to both cyromazine and abamectin, and a cyromazine-resistant strain and an abamectin-resistant strain, it was found that two oligonucleotides amplified unique bands in the cyromazine-resistant strain but not in the reference or abamectin-resistant strains. Three oligonucleotides showed polymorphisms unique to the abamectin-resistant strain but not in the reference or cyromazine-resistant strain. This method can be used to quickly identify cyromazine and/or abamectin resistance in leafminers enabling a grower to choose an effective insecticide.