Output 2: Evaluation of local African deposits of DEs against storage insect pests

Progress report:

Tanzanian diatomite from Kagera river basin

Although the DEs, Protect-It and Dryacide come from America and Australia respectively, DE deposits can also be found in East and Southern Africa. Samples from: Kagera river, Tanzania; Zambezi valley and Beitbridge, Zimbabwe; South Africa and Zambia were collected and sent to Canada for analysis of their potential efficacy as insecticides. Attempts are still being made to obtain a sample from the Bahi area of Dodoma in Tanzania.

Although rapid assessment results (Diatom Research and Consulting, Canada) on the efficacy of the African DEs suggested none of them could be classified in the high potential insecticidal efficacy class, when compared with other raw DEs from China and elsewhere. When these African DEs were applied at higher application rates of 2500ppm in laboratory tests (NRI, UK) against Sitophilus zeamais the emergence of progeny insects was reduced by 80% or more after 7 weeks in all the African DE treatments in comparison to the untreated control. These results suggest that if these African DEs could be easily accessed, were found to have low crystalline silica contents and the application rate of 2500ppm was acceptable to farmers, then they could offer the region a new and possibly cheaper grain protection option.

In Tanzania, a sample from the Kagera river, Nyakanyasi rocks deposit has been included in the 2003/2004 seasons field trials at Mlali village, Dodoma region (using an application rate of 250g/100kg maize). In Zimbabwe, plans are underway to includea purer sample of the Beitbridge (Limpopo valley) deposit in on-station trials at IAE during the 2003/2004 storage season.