Assessment of the Harlequin Ladybird's (Harmonia Axyridis) Resistance to the Most Commonly Used Active Substances in Insecticides

Abstract

The objective of this study was to find out if useful insects - in this case, harlequin ladybirds (Harmonia axyridis) - are affected by plant protection products (PPP) to the same extent as pests and if this species shows any levels of resistance to chosen active substances in insecticides. Harlequin ladybirds were collected in selected localities during the 2019 vegetation season. Their resistance to active substances (lambda-cyhalothrin and thiacloprid in various concentrations) was then tested. In the thiacloprid test, the commercial formulation of Biscaya 240 OD was used. Testing was performed pursuant to the Insecticide Resistance Action Committee (IRAC) methods using the adult-vial-test. The efficiency of the active substance used was assessed, and tested individuals were divided into groups (Alive, Dead, or Tremor) according to their physical condition. From the values obtained, mortality was calculated at 100% of the dose of each active substance. Subsequently, the results were elaborated using the specialised program of POLO PLUS 2.0, which calculates the values of a lethal dose - LD50, LD90 and LD95. Mortality was assessed depending on the dose increase of tested active substances. According to the mortality assessed and calculated lethal doses, it was observed that populations of the harlequin ladybird are sensitive to the affect of tested active substances. Since these are one-year results, it is difficult to determine if a selection of resistant populations will occur.