The occurrence and distribution of resistance of codling moth to <i><scp>C</scp>ydia pomonella</i> granulovirus in <scp>E</scp>urope

Abstract

Abstract Thirty‐five codling moth ( CM , C ydia pomonella L ., L epidoptera, T ortricidae) populations collected in different commercial orchards in six European countries were tested for their susceptibility to C ydia pomonella granulovirus ( C p GV ‐ M ). Including previously published data on C p GV ‐ M resistance, a total of 38 CM colonies showed considerably elevated LC 50 values, independent of the country origin. When only few test individuals are available, determination of mortality of neonate larvae at a discriminating concentration range of 10 4 to 10 6 OB/ml (&gt;log4) as a direct measure of percentage susceptible individuals in a CM population is more advisable than calculation of LC 50 values. The &gt;log4 mortality alone or in combination with the LC 50 value can be used for identification of resistance in a population. Results indicated a locally separated but widely spread occurrence of CM populations with low susceptibility to C p GV ‐ M . The most plausible hypothesis for the emergence of C p GV ‐ M resistance is its selection by repeated use of C p GV products.