N mme-v rgendivaablase (Acantholyda posticalis (Mats.), Hymenoptera: Pamphiliidae) esmakordne hulgisigimine Eestis

The most common defoliating insect species in Scots pine (Pinus sylvestris) forests of Estonia are the European pine sawfly, Neodiprion sertifer (Hymenoptera, Diprionidae) and the pine looper moth, Bupalus piniaria (Lepidoptera, Geometridae). The great web-spinning pine-sawfly, Acantholyda posticalis (Matsumura 1912) (Hymenoptera, Pamphiliidae), is a common and widespread species, occurring throughout the pine forests of Europe and Asia. Mass outbreaks of this species have been recorded in Scots pine stands of Central and Eastern Europe, northern Kazakhstan and Siberia. In northern and Western Europe, the species usually occurs sparsely. In the recorded history of forest entomology of Estonia, no mass outbreaks of this species have been reported before. In 2008, an outbreak of A. posticalis was recorded on the island of Saaremaa in western Estonia. About 250 hectares of pine stands in age of 60-100 years growing mainly on sandy soils were defoliated. The 30-50-yearold pine stands were also damaged. In 2009, no flight of A. posticalis was observed; the larvae remain in diapauses in soil. An overview on distribution and outbreaks of A. posticalis in pine forests is given and its impact on stands is discussed.