Many cereal stem borers undergo a resting period toward the end of the cropping season in response to cold and/or dry conditions. The resting period is spent as mature larvae within dry crop residues and stubble in the fields.
In the elevated regions of southern Africa, B. fusca and C. partellus pass winter (May to September), which is the cold dry season, in diapause in the lower portions of the dry stalks of their host plants, where they are well protected from adverse climatic conditions. In West Africa, B. fusca also enters a prolonged diapause during the dry season, which takes up to six months to complete. With the start of the rains, the larvae pupate within the stems and 10–12 days later emerge as adult moths.
While B. fusca diapauses throughout its distribution range in Africa, the larvae of C. partellus do not undergo diapause in the warmer low-lying South African provinces of Kwazulu-Natal and Mpumalanga, Swaziland and southern Mozambique. Likewise, while C. partellusis...