Browsing by Subject "Acantholyda posticalis"

The great web-spinning pine-sawfly is a common species in Finland. Few mass outbreaks have occurred in Europe, but they have last a long time. Yet first outbreak in Finland was observed at Yyteri region near Pori in 2006. Larvae use pine needles as nutrient. It is estimated that 100–200 larvae/m2 is a level for severe forest damage. There have been many locations containing 200–500 larvae/m2 at the Yyteri region. There is tourism and nature value in Yyteri and so chemical control was not the first option. That is why biological control was used and the most promising seem to be Steinernema feltiae. It was commercially available and spraying it was simple. The purpose of the research was to find out how S. feltiae could be used to reduce the great web-spinning pine-sawfly on a large scale. Spraying was done by using agricultural spraying equipment attached to tractors. Photoelecton traps were used and soil samples of larvae were collected. Control traps gathered 65.0 % of adults in 2011 while treatment traps gathered 35.0 %. In 2012 traps collected 48.6 % and 51.4 %, respectively. Traps gathered 120 adults in 2011. Main swarming was 2012 and 469 adults were caught. Some unreliability is involved in results because of the high spatial distribution of larvae in soil. Differences between years might be explained by earlier metamorphosis of the great web-spinning pine-sawfly to adult, increased deviation of trap results and grassier field conditions. Chilly weather might also have prevented nematodes performing at maximum capacity in 2012. In soil samples 88.6 % of the great web-spinning pine-sawflies were alive. It seems that most of them would be overwinter for fourth year. Most of the dead great web-spinning pine-sawflies (90.3 %) were found in organic soil layers. However, the clear-cut area has stayed at 200 ha for now.