To browse Academia. Five raw African diatomaceous earth DE samples collected from Tanzania, Zimbabwe, Zambia and South Africa were compared in laboratory bioassays at the Natural Resources Institute, UK and the University of Zimbabwe, to determine their potential as locally available grain protectants. In UK, each sample was tested at two concentrations 2, ppm and 5, ppm, whereas in Zimbabwe an additional concentration of 1, ppm was included.
These concentrations are higher than those at which commercial DEs are commonly used, but much lower than the concentrations at which farmers in sub-Saharan Africa SSA typically admix traditional protectants such as ash and sand with their commodities during storage. After the day mortality count, all the adult insects were removed, and the grains retained under the same conditions for F1 progeny emergence assessment 7 weeks from experiments commencement.
These results suggest that if sufficient supplies of the African DEs with the low crystalline content could be easily accessed, then they could offer small-scale farmers in SSA an alternative and possibly cheaper grain protection option to the organo-phosphate-based pesticides many are currently using on their stored grain.
Farmers and grain traders in sub-Saharan Africa are forced to sell stored produce prematurely because of deterioration due mostly to insect damage. Producers expressed a need for a relatively cheap and safe method of insect control. Diatomaceous earths DE offer safer alternatives to synthetic chemicals, but information on their efficacy under tropical small-scale farming conditions is lacking.
Two commercially available DE products, Protect-It s and Dryacide s , were tested against the major post-harvest insect pests of grains and pulses. On-farm field trials in Zimbabwe showed that both inert dusts gave significant protection against insect damage when admixed with farm stored maize, sorghum and cowpeas for periods of 40 weeks.
