Kill the Stem Borer, Save the Stem
The sorghum stem borer, Busseola fusca, is the most important stem borer in Africa south of the Sahara and may account for overall crop losses of 5-10% in some sorghum growing areas. Traditional storage and use of the stalks for building houses, fencing, and for fuel ensures the survival of the sorghum borer, as diapausing larvae are able to survive a six-month dry period in the harvested stems of the preceding crop. Partial burning or “curing” the newly harvested stalks resulted in 95% eradication of the larvae and left the stalks intact, stronger, and slower to burn than the uncured stalks. Equally successful was the technique of thinly spreading the harvested stalks in an open field, as opposed to the traditional method of stacking stalks in vertical or horizontal piles, either in the open or in the shade.
Researchers at the Institute for Agricultural
Research in Nigeria compared five treatments of stalks for the survival of B.fusca in an experiment conducted both on local farms and at the institute.
For treatments that involved curing, stalks from separate rows were first piled in furrows. These stalks were burned within three days of harvesting for 5-10 minutes, removing the dry leaves.
After harvest in December, five trials were conducted:
uncured stems spread thinly in an open field
cured stems stacked upright in an open field
cured stems stacked upright in the shade
uncured stems stacked upright in an open field
uncured stems stacked upright in the shade
At the end of the dry season in mid-April, five stacks of each treatment were randomly chosen, sampling 40 stems from each stack (20 from the outside layer and 20 from the inside). Twenty stems were also sampled from the unstacked treatment. The stems were split open and the larvae counted. Larvae were raised to maturity to confirm that they were B. fusca.
Higher temperatures and lower humidity resulted in fewer surviving larvae. Complete eradication of B. fusca larvae was found among the uncured stalks that had been spread in an open field. Uncured stalks stacked in the shade showed the lowest mortality rate with 20%, and uncured stalks stacked in the open resulted in 60% mortality. Cured stalks stored in the open had a 95% mortality, as did cured stalks stored in the shade.
The Ministry of Agriculture in the region recommends that farmers either completely incinerate the stalks, or spread them in the field. Neither solution has been adopted by the farmers, because they consider the stalks a valuable resource. However, by curing the stalks, farmers eliminate B. fusca larvae without depriving themselves of an important exploitable resource.
Adesiyun, A.A., and Ajayi, O.(1980). Control of the sorghum stem borer, Busseola fusca, by partial burning of the stalks. Trop. Pest Mgt. 26(2): 113-117.
For more information:
Institute for Agricultural Research
Ahmadu Bello University, Samaru, Zaria