Epsilon Archive for Student Projects

Abstract

Insect pests are a major cause for damages in forestry, especially in monocultures. Early pest detection allows for rapid use of protective measures to reduce their impact, and abundance estimation is used to predict the scale of necessary actions. Environmental DNA (eDNA) surveys are a promising method for pest detection, but their usefulness for insect abundance estimation is not well understood.
In this study, samples containing Ips typographus specimens preserved in propylene glycol collected in Picea abies monocultures and mixed forests in two locations in Southern Sweden were used to evaluate the usefulness of eDNA surveying for spruce bark beetle detection and abundance estimation. Collected specimens were counted and eDNA was collected from preservation fluid using paper filters and extracted. Quantitative PCR and a set of probes and assay were used to detect Ips typographus DNA. Relationship between quantification cycle and DNA quantity was analysed to check if the method can be used for pest detection. Beetle count and DNA quantity relationship was analysed to check if eDNA survey can be used for abundance estimation. Differences between beetle counts in both locations and forest types were analysed to confirm the species composition effect on pest abundance.
The results affirmed eDNA survey effectiveness for pest detection. Positive monotonic correlation between beetle count and DNA quantity was detected, but small data sample and high variation currently limit the method’s usefulness for pest abundance estimation. Beetle count comparisons suggest Ips typographus produced one generation in a location close to the coast, and two populations further inland. Beetle count between the two forest types did not differ significantly.
Future research into eDNA sampling for pest abundance estimation is needed. Multi-year validation including during outbreak years of Ips typographus could produce more definitive results.