Phenology and pest status change of Agrotis segetum related to climate changein Northwest Europe

Abstract: Cutworm, the larva of the Turnip moth (Agrotis segetum Schiff.) is known as astrongly varying pest species in NW Europe. Monitoring by sex pheromone trapping is a vitalpart of pest management. In Denmark the number of localities involved has varied over the yearsbut the monitoring methodology has been unchanged since 1981. Therefore it is possible to tracesome phenological changes in response to the gradually warmer climate and suggest explanationsto the apparent changes in its pest status over the last decade.Due to the rising summer temperatures the median date of the trapping (flight) period is nowapproximately 8 days earlier than in the 1980s, and the previously negligible second generationof moths may be as large as the first generation. In Denmark and southern Sweden the earliermean flight period in combination with a higher risk of dry periods in summer increases the riskof serious attacks of cutworms. However, the second moth generation is lost to the population inthe following year. In addition climate change also involves an increased probability of extremeprecipitation events. If several very rainy days coincide with the presence of the youngestcutworms, they will suffer high mortality. The end result of these contradictory possibilities isincreased variation, geographically as well as between years, and hence a more difficultforecasting situation.