Dissemination of the mycoparasite Scytalidium uredinicola by Epuraea obliquus (Coleoptera : Nitidulidae)

Abstract

This study aims to identify the role of the beetle Epuraea obliquus Hatch in disseminating Scytalidium uredinicola Kuhlman et al., a mycoparasite of western gall rust, Endocronartium harknessii (J.P. Moore) Y. Hiratsuka. The study was conducted in a lodgepole pine, Pinus contorta Dougl. var. latifolia Engelm., stand near Hinton, Alberta. Mycoparasite spores were observed on the integument of adult beetles collected from western gall rust. In field and greenhouse experiments, adult beetles inoculated with spores of the mycoparasite caused significant numbers of S. uredinicola infections on western gall rust. Since E. obliquus adults migrate between galls, the beetle can transfer the mycoparasite from parasitized to unparasitized galls. Scanning electron microscopy showed that spores of the mycoparasite were common on the body of overwintering beetles. It is believed that these overwintering spores are viable because a culture was successfully established from them. This suggests that beetles emerging in the spring can disseminate S. uredinicola to previously uninfected galls. Epuraea obliquus is an important insect vector of S. uredinicola in western Canada. Key words: mycoparasite, vector, spore dispersal, western gall rust, pine stem rusts.