Correlations between susceptibilities to lambda-cyhalothrin and chlorpyrifos-ethyl with respect to thiacloprid in Czech populations of Meligethes aeneus

Abstract: Populations of Czech Meligethes were simultaneously tested for susceptibility to lambda-cyhalothrin and chlorpyrifos-ethyl and also to lambda-cyhalothrin and thiacloprid in 2014. In 2015, Meligethes populations were again tested for susceptibility to lambda-cyhalothrin and chlorpyrifos-ethyl and to lambda-cyhalothrin and thiacloprid simultaneously, this time using populations of mainly Czech but also Slovak origin. IRAC adult vial tests were used. IRAC no. 011 v. 3 for lambda-cyhalothrin, IRAC no. 025 for chlorpyrifos-ethyl and IRAC no. 021 for thiacloprid. For each of the tested populations the LC50 and LC90 values for the three insecticides were determined. Correlation analyses were made with transformed (log10) LC values. Significantly negative correlations were recorded for the LC90 and LC95 values estimated for the correlation between lambda-cyhalothrin and chlorpyrifos-ethyl. Pyrethroid resistance in pollen beetle populations should indicate their slightly higher susceptibility to chlorpyrifos-ethyl. Contrary to expectations, significant positive correlations were recorded for the LC50, LC90 and LC95 values for the correlation between lambda-cyhalothrin and thiacloprid in both years. Pyrethroid resistance in pollen beetle populations should indicate their lower susceptibility to thiacloprid.