Natural products in stored product pest control: challenges and opportunities

Abstract

Postharvest losses of stored grains are recognized as a major constraint in food security. Thus, the reduction of losses caused by stored product pests (insects, microorganisms and rodents) can increase available food supplies. The control of pests in storage and processing industry is mainly relying on the use of chemically synthesized pesticides and toxic fumigants. However, due a ban or restriction of a number of insecticides, there is an expansion in use of natural products (particularly inert dusts and botanicals). The efficacy of several inert dusts (diatomaceous earth - DE, kaolin clay - KA and vermiculite - VE (5, 7.5, 10, 15 and 20 gm-2)) and plant extracts of weed and invasive plant species (Erigeron cannadensis, Daucus carota and Halacsya sendtneri (0.5, 1 and 2%)) in suppressing the Sitophilus oryzae weevils was evaluated in contact toxicity tests. DE caused significant mortality at rates 10 (67.8%), 15 (75.3%) and 20 gm-2 (98.2 %), as well as KA (75%) at 10 gm-2, after 24 h. The mortality increased with the exposure period, so in both cases, after 72 h, the mortality was very high (97.8 – 100%), regardless on the applied rates. However, VE as well as plant extracts exhibited very low insecticidal activity, since the mortality was 0-17.5%, and 0-11%, respectively.