Insecticide resistance in Colorado beetles: no let up.

摘要

Causes for increasing numbers of insecticide-resistant Leptinotarsa decemlineata in European potato fields are discussed. Laboratory testing with the IRAC no. 7 method was carried out with 4 pyrethroids, 2 neonicotinoids, and benfuracarb. Polish farmers have been noting control problems since 8-9 years and studies in 1999-2000 confirmed pyrethroid resistance. German studies in northern Rheinland-Pfalz during 2003-06 showed the development of resistance to lambda -cyhalothrin. LD-95 data were related to field application data, showing that the theoretical efficacy of 92% in 2003 decreased to 73% in 2006. However, actual efficacy in the field was much lower (20-40%). Studies at 5 locations in Rheinland-Pfalz investigated carbamate (as benfuracarb) resistance in local beetle populations. No resistance was only found at one location where benfuracarb was never used before. All other locations showed high insecticide resistance. Strategies to prevent resistance formation are discussed, based on application only if damage threshold is exceeded (15 larvae/plant), optimal application time (maximum young larvae presence), and changing insecticides used.