Kann sich der Speisebohnenkäfer Acanthoscelides obtectus Say als Freilandschädling in Norddeutschland einbürgern? (Coleoptera: Bruchidae)

Summary The occurrence of Acanthoscelides obtectus outdoors in N. Germany is helped because attacked seed is put out; garden owners are often aware of this. The climate at the time of sowing and the epigeal germination of the beans facilitates the emergence of the beetles but with cold and in alkaline soils, they rot with the beans. The beetles can survive throughout the summer and remain capable of reproduction because they are feeding and also the weather is relatively cool and damp. Egg laying is usually possible until the end of September and larvae can still hatch outdoors in August; later, the development takes place in the storehouse. With suitable storage of the beans, the beetles can increase and return outdoors in the Spring with the sowing. They thus pass the summer as outdoor insects and the winter as stored products pests, this regular alternation is characteristic of the insect in N. Germany. The sudden increase in attack due to outdoor infection is explained by the increase in bean growing in the years after the war, an adaptation to the climate is not involved. The beetle does not originate from the tropics but from high places in the S. American mountains where the wild form of the bean also grows.