THE BIOLOGY AND POPULATION-DENSITY OF THE WILLOW BEETLE (PHRATORA-VULGATISSIMA(L)) ON SALIX-VIMINALIS IN RECLAIMED CUTAWAY PEAT

The life cycle and population ecology of Phratora vulgatissima (L.) were studied in Salix viminalis plots on cutaway peat at Clonsast, Co. Offaly during 1982 and 1983. Development time from the first appearance of larval instar I to ecloded adult emergence was ca 6 weeks; the duration of the pupal stage was about 2 weeks. Adults overwintered in crevices and under bark of Salix caprea in an adjacent hedgerow. Larvae were significantly more abundant on internal than on distal branches, on widely spaced than on narrowly spaced trees, and on coppiced than on uncoppiced trees. Maximal mean densities in 1982 when the trees experienced significant moisture stress were 607 larvae and 308 adults per tree. Population densities in 1983 were considerably lower (max. mean densities 154 larvae and 72 adults per tree).