Epsilon Archive for Student Projects

Abstract

The Eurasian spruce bark beetle Ips typographus (Linnaeus) is a serious pest of Norway spruce Picea abies (L. Karst) forests in Sweden and large parts of Europe and Asia. Problems are expected to become worse due to climate change. The use of conventional control measures such as cutting, and removal of infested wood and use of pheromone traps are sometimes not enough to manage the pest. Flies in the genus of Medetera are native to Sweden and the larvae are important natural enemies of I. typographus. This gives rise to the possibility of the genus of Medetera (Fischer) to be used for the biological control of the Eurasian spruce bark beetle.
This project aimed to investigate several behavioural and ecological aspects of flies in the genus of Medetera such as odour-guided behaviour and prey finding mechanisms. An artificial diet based on spruce phloem was developed to test for the survival rate of Medetera spp. larvae under laboratory conditions. Two choice bioassays in Petri dishes were designed to test the response of Medetera spp. larvae to compounds produced by I. typographus or to the symbiotic blue-staining fungus Grosmannia penicillata grown on agar or on agar containing spruce phloem. Field trials were also performed, using self-made traps containing blends of volatiles to specifically evaluate the attractiveness of certain volatiles directly connected to or produced by I. typographus during phases of infestation.
This study demonstrated that Medetera spp. larvae can be reared on larvae of I. typographus which have been reared on an artificial diet based on phloem from Norway spruce. Results from field trapping suggests that adult Medetera spp. flies are attracted to the volatile cis-verbenol, and laboratory assays indicate that larvae are also attracted to this volatile, known as one component of the aggregation pheromone of I. typographus. The compound trans-verbenol is also attractive to larvae and possibly also adult Medetera spp.