Recent evolution and operational impact of insecticide resistance in olive fruit fly Bactrocera oleae populations from Greece

Abstract

The major problem of olive fruit protection in the Mediterranean basin is the control of the olive fruit fly Bactrocera oleae. The aim of this study was to investigate the status of resistance against insecticides which are registered and used against this major olive pest in Greece. During a 9-year survey, 55 B. oleae populations were collected. Insecticide application records showed extensive use of pyrethroids (alpha-cypermethrin) and to a lesser extent macrocyclic lactones (spinosad) and organophosphates (dimethoate). Low-to-moderate resistance levels were identified in the majority of populations for alpha-cypermethrin until 2012. After 2013, however, a dramatic increase of alpha-cypermethrin resistance was observed, especially in populations from Crete, Greece. The phenotype has an obvious impact on control efficacy. In real-field-cage trials, the mortality of the pyrethroid resistant field population from Crete was dramatically lower compared to the mortality of a respective field population from Samos with low-resistance level. Low-resistance levels were observed for spinosad in most of the populations tested. The frequency of the organophosphate resistance mutations G488S and I214V remained very high across most populations in Greece, despite the reduction in the application of these insecticides in the last decade. In contrast, the frequency of the mutation Δ3Q was very low. In conclusion, field evolved and practical resistance against alpha-cypermethrin seems to be emerging in B. oleae populations from Greece. It needs to be monitored and further characterised for the application of evidence-based control strategies.