The correlation between the susceptibilities to lambda-cyhalothrin and tau-fluvalinate in Czech and Slovak pollen beetle populations

Abstract

A total of 251 pollen beetle (Brassicogethes aeneus F.) populations sampled in the Czech Republic and Slovakia were tested against both lambda-cyhalothrin and tau-fluvalinate by means of Insecticide Resistance Action Committee (IRAC) susceptibility test method 11, version 03 (glass vial test) over four (2015-2018) years. The results confirmed high levels of resistance to lambda-cyhalothrin in the pollen beetle populations of both countries. Tau-fluvalinate is less affected by resistance, but relatively high proportions of resistant populations at many localities in both countries make this insecticide almost unusable against the pest too. The results of a correlation analysis of lethal concentration (LC) values (LC 50 and at least partly of LC 90 values, too) indicate a moderate level of cross resistance against the two active ingredients in Czech populations. In Slovakian populations, the positive correlation between the LC 50 values proved to be significant only in 2018 (r = 0.66, p < 0.001). Despite certain variability in the results of the correlation analysis recorded in this study, the findings indicate another possible decrease in the susceptibility of pollen beetles to pyrethroids, in general, if tau-fluvalinate were used for their control under field conditions.