Efficacy of Ethanol Extracted Selected Botanicals and Diatomaceous Earth against Maize Weevil, Sitophilus zeamais Motsch. (Coleoptera: Curculionidae) in the Laboratory

Abstract

Ethanol extracted three botanicals (Azadirachta mdtca. Chenopodium ambrosoides
& Maesa lanceolata) and diatomaceous earth (DA) were tested to evaluate their
effectiveness against maize weevil, Sitophilus zeamais M. They were applied at three
rates of 0.3, 0.4 and 0.5 ml/g per 250 g of grain and compared with untreated control,
ethanol treated control and Malathion super dust as a standard check. The study was
laid-out in completely randomized design with three replications. Data were
collected on cumulative adult mortality, median lethal concentration, median lethal
time, F| progeny emergency, and grain damage. The results revealed that, higher
mortality of S. zeamais was observed from ethanol extracts of C ambrosoides
(98.3% with LT50 of 1.13 days), A. indica (97.5% with LT50 of 1.26 days), and
diatomaceous earth (100% with LT50 of 1.33 days) at 0.5ml/g after 21 days of
exposure periods. Apart from the untreated and ethanol treated controls, the lowest
cumulative adult mortality of S. zeamais was recorded from extracts of M. lanceolata
(58.4% with LT50 of 17.62 days) at 0.3ml. The LC5(, indicated that C. ambrosoides
extracts (0.23g/250g of maize) was the most toxic at minimum concentration while
M. lanceolata extracts and diatomaceous earth (0.27g) was the least potent to weevil
at lower concentration. No F| progeny emerged from the grains treated with the
former three treatments similar to the standard chemical leading to no seed with hole,
no weight loss and maximum germination percentage (93.50- 95.2%). The study
demonstrated that the extracts and DE at their higher concentration/dosage can be
used as components of maize weevil integrated management option.