Forecasting the breaching of the control threshold for Ceutorhynchus pallidactylus in oilseed rape

The cabbage stem weevil Ceutorhynchus pallidactylus (Mrsh.) (Col.: Curculionidae) is a common pest in oilseed rape Brassica napusL. throughout Europe. The abundance of the cabbage stem weevil was monitored in field surveys by using yellow water traps between 2007 and 2012 at five locations in Luxembourg. We forecast the abundance of the cabbage stem weevil at levels above the control threshold in oilseed rape in springtime. If mean winter temperatures between 5 and 13 February are closer to 4.0 degrees C than to -2.4 degrees C, no breaching of the control threshold is to be expected in the subsequent March. The monitoring effort might be saved in those years. Leave-one-out cross-validation revealed that whether the control threshold was exceeded could be correctly predicted based on the observed temperature differences identified in 22 out of 27 cases (81.5%) in the present study. The present approach can be easily transferred to regions where air temperature data are available, although it should not be used without prior local validation.