Dendrosoter protuberans (Hymenoptera: Braconidae), An Important Elm Bark Beetle Parasitoid

Abstract

The most favourable period for Dendrosoter protuberans development occurred when wasps were introduced 16 days after the beginning of Scolytus multistriatus development (the greatest number of emerged wasps per a single parasitoid female with a very positive sexual index and high percentage of parasitised elm bark beetle larvae). No significant differences were observed in parasitoid efficiency between the 11^th and the 21^st day. The most unfavourable period for elm bark beetle parasitisation was six days after the beginning of S. multistriatus development (a low reproduction of D. protuberans, a negative sexual index and a low number of destroyed S. multistriatus larvae). The reproduction of both the elm bark beetle and D. protuberans was greater in the first, than in the second generation. The developmental period of D. protuberans in the first generation was approximately two days longer than in the second generation. Furthermore, the development of females was 1–2 days longer than the development of males. D. protuberans developed most successfully on S. multistriatus (the most abundant parasitoid reproduction with the longest developmental period and a very positive sexual index that resulted in a high percentage of parasitised larvae) and then on S. ensifer, S. pygmaeus and Pteleobius kraatzi. On the other hand, S. scolytus larvae were the poorest host of all elm species – the reproduction of D. protuberans in this species was the scarcest with the shortest period of development and a negative sexual index, hence larval parasitisation was the lowest.

Keywords:

• elm bark beetle
• parasitism
• Dendrosoter protuberans
• Scolytus multistriatus
• Scolytus scolytus
• Scolytus pygmaeus
• Scolytus ensifer
• Pteleobius kraatzi