Natural enemies of Ips subelongatus in Aershan area of Inner Mongolia and their suppressive effects
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Key Words：Ips subelongatus, natural enemy, suppressive effect
Abstract： The natural enemies of Ips subelongatus Motschulsky (Coleoptera, Scolytidae) were investigated in Aershan, Inner Mongolia. The most abundant species were the predatory beetle Thanasimus substriatus Gebler (Coleoptera, Cleridae) and the parasitic wasps Tomicobia seitneri (Ruschka) (Hymenoptera, Pteromalidae) and Coeloides bostrichorum Giraud (Hymenoptera, Braconidae). In addition, some yet unidentified parasitic mites and pathogenic organisms were also recorded. The natural suppressive effects of the predators and parasitoids were analysed. Average preying rate per day of T. substriatus to I. subelongatus adult was (3.1±0.77) % (20 I. subelongatus with 1 T. substriatus, 12~24℃ outdoors), and the maximum predation was 10.7 Ips beetles per day (1 T. substriatus with 20,40,60,80,100 I. subelongatus, 17~25℃ indoors). The parasitic rates of T. seitneri to I. subelongatus larvae and pupae were 20. 5 % and 13.7 %, respectively. The parasitic rate of C. bostrichorum to I. subelongatus larvae was 6.5%. The parasitic rate of mites to I. subelongatus adults was 20.2%; and the parasitic rate of pathogenic organisms to I. subelongatus was 4.3 % (larvae), 5.4 % (pupae) and 2.1 % (adults). Our results indicate that T. seitneri is probably the most potential candidate for biological control of I. subelongatus.