Pine weevil update March 2015
In our BIOCOMES research we work on the optimization of the strains of entomopathogenic nematodes to use as an effective biological control agent against large pine weevil in clear-felled coniferous forests.
In the first year at National University of Ireland Maynooth (NUIM) and the Forest Research Institute (IBL) we have compared two entomopathogenic nematode species (Steinernema carpocapsae and Heterorhabditis downesi) in their capability to suppress pine weevil in roots of stumps. Previous studies indicated that the nematode species Heterorhabditis downesi seemed to be the most effective nematode species. We are investigating the effect of soil type, because nematodes are predicted to be more effective in deep peat soils. We are also assessing whether the application method of the biological control agent can be optimized.
Three small scale field trials have taken place in Ireland and in Poland. In Ireland the Steinernema and Heterorhabditis nematode species appeared effective in deep peat soils in field tests. This was measured by the number of emerging adult weevils and the amount of immature pine weevils that were parasitized by the nematodes. The effectiveness in shallow peat is still being investigated. In Poland the use of nematodes caused 15-17% mortality of Hylobius larvae developing in treated stumps. A low level of parasitism was caused by unfavourable conditions for nematode development (drought). In the next year, we will test different methods of nematode application to minimize the impact of weather condition on the nematode activity.
Optimizing the application method
The best application method of the nematode treatment appeared to be different for the two nematode species. Heterorhabditis downesi provided better control when applied on top whereas Steinernema carpocapsae provided better control when applied around the stump. The application method on dispersal and efficacy of both species are being further investigated in field trials in Poland and Ireland.
Read more about our activities on large pine weevil.
Picture 1: Nematode application poured around the stump.
Picture 2: Nematode application poured at top of stump.