THE DISTRIBUTION AND IMPORTANCE OF THE CLOVER ROOT BORER (HYLASTINUS OBSCURUS (MARSH) COLEOPTERA: SCOLYTIDAE) IN QUEBEC

Abstract

The clover root borer, Hylastinus obscurus (Marsh), occurred throughout western, southern and central Quebec in 1954. The roots of from 28 per cent to 94 per cent of the plants in some red clover stands became infested during the spring and summer of the second and third years of growth. Infestation intensity was not correlated with soil pH or texture.Borer adults spread from the point of origin during a brief flight in the spring.A cantharid larva, an adult staphylinid (Grohypnus sp.) and unidentified dipterous larvae were observed feeding on borer larvae.Lindane applied in the spring increased clover hay yields on artificially infested plots.The larger plants were more commonly infested and also more commonly infected with root rots. Laboratory experiments indicated that activity of adult borers could help to initiate fungal infections.Very few plants which survived a second winter showed infestation in the following spring.