Submitted to: USDA Interagency Research Forum on Gypsy Moth and Other Invasive Species
Publication Type: Abstract only
Publication Acceptance Date: 8/20/2006
Publication Date: 10/20/2005
Citation: Sukovata, L., Fuester, R.W. 2005. Effects of Gypsy Moth Population Density and Host-Tree Species on Parasitism, P79. In K. Gottschalk (ed.), Proceedings, 16th US Department of Agriculture Interagency Research Forum on Gypsy Moth and Other Invasive Species 2005. Gen. Tech. Rep. NE-337, USDA Forest Service, Newtown Sq., PA. Interpretive Summary:
Technical Abstract: The gypsy moth (Lymantria dispar L.) is a defoliator of deciduous forests throughout most of Eurasia and the northeastern part of the USA. In Poland, the economic importance of the gypsy moth is rather low. Sporadically it causes local outbreaks, which are suppressed by a complex of natural enemies, mostly virus and parasitoids. These studies were conducted in 2003 and 2004 in the Biebrza National Park located in the northeastern Poland. The research was conducted at three sites characterized as follows: Kopciowe (sparse gypsy moth population in both years), Barwik (outbreak in 2003 and post-outbreak in 2004), and Honczarowska (outbreak in 2004). At Kopciowe, we used trap larvae that were reared in the laboratory from egg masses collected in the field and exposed 3-4 times during the season on oak saplings placed in 3-5 cages covered with netting. At Barwik and Honczarowska, gypsy moth larvae were sampled 4-5 times during the season from 4-5 species of trees (40-50 larvae/tree species/site): Alnus glutinosa, Salix cinerea (only at Barwik), Betula spp., Quercus robur and Corylus avellana. Larvae collected were reared individually on fresh oak leaves in plastic cups. Parasitism at Barwik was up to 44.6% in 2003, but decreased to 34.7% in 2004. In the outbreak phase the co-dominant parasitoid species were Blepharipa spp. (up to 35.3%) and Parasetigena silvesris (up to 9.2%), whereas in the post-outbreak phase, P. silvestris was more efficient (24% max. peak parasitism) than Blepharipa spp. (12.7% max. peak parasitism). At Honczarowska, the total parasitism in 2004 reached 67.8%, due mostly to P. silvestris which parasitized 52.8% of the larvae. Blepharipa spp. (schineri and pratensis) were subdominant (up to 19.8% parasitism). In the sparse population, total parasitism was up to 39% in 2003 and 48% in 2004. The dominant parasitoid species were Compsilura concinnata (up to 31.8%) in 2003 and Aphantorhaphopsis samarensis (up to 43.2%) in 2004. The results of two-year studies showed no consistent relationship between gypsy moth parasitism by Blepharipa spp. and P. silvestris and the tree species from which host larvae were collected. In 2003, parasitism by both species was higher on Alnus and Betula than on Salix, but in 2004, parasitization by Blepharipa was highest on Salix, which had the highest gypsy moth density and concomitant defoliation, whereas parasitism by P. silvestris was lowest on the same host plant, suggesting that defoliation can also be a determinant of parasitism.