Investigation on the parasitoids and pathogens of Asian corn borer overwintering larvae in the corn belt of China.
The parasitoids and pathogens of Asian corn borer (Ostrinia furnacalis) overwintering larvae were investigated in 11 geographically distinct locations of 9 provinces of the maize growing area in China. A tachinid fly, Lydella grisescens (Diptera, Tachinidae), a braconid wasp, Macrocentrus cingulum (Hymenoptera, Braconidae), and an ichneumon wasp, Eriborus terebrans [Diadegma terebrans] (Ichneumonidae), were the major parasitic insects. Beauveria bassiana, Bacillus thuringiensis and two microsporidia, Nosema furnacalis and Nosema sp., were the major pathogens. In general, O. furnacalis mortality caused by pathogens was higher than by parasitic insects. Muscardine was the most prevalent disease, especially in the spring maize area. The incidence was as high as 74.8-80.4% in Dunhua and Gongzhuling of Jilin. B. bassiana was commonly used as microbial-pesticide to control O. furnacalis in these area. B. thuringiensis was more prevalent in the summer maize area. The incidence was 6.7-13.7%. N. furnacalis prevailed in the spring maize area, and Nosema spp. was distributed in the summer maize area. Braconid wasps were widely established in the summer maize area and attacked 0-17.9% of O. furnacalis larvae. E. terebrans was most abundant in Chifeng of Intra-Mongolia, Shuozhou of Shanxi, and Dunhua, and attacked 1.5, 0.5, and 0.8% of O. furnacalis larvae, respectively. The tachinid fly was prevalent in all locations except in Chifeng and Hengshui of Hebei, and most abundant in Shuozhou. The parasitism was 0.7-6.3%.