A survey of the incidence and abundance of insect pests of stored groundnuts in the Ibadan area of Nigeria

MBATA, G.N.

ABSTRACT: A survey to ascertain the incidence and relative abundance of insect pests of stored groundnuts was carried out at Sabo Village, near Dugbe market, Ibadan, between April 1981 and April 1982. The most abundant insect pest was Tribolium castsaneum (Herbst) which represented 51.9% of insects trapped on the wing and 72.7% of insects sieved from groundnut samples.

Ephestia cautella (Walker) constituted 30.2% of trapped flying insects and 12.0% of insets sieved from samples; Plodia interpunctella constituted 11.3% of trapped flying insects and 9.2% of insects sieved from samples; Corcyra cephalonica (Stainton) constituted 5.7% of trapped flying insects and 4.9% of insects sieved from
samples; and Oryzasephilus mercator (Fauvel) constituted less than 2% of both trapped and sieved insects. The peak of infestation of groundnut samples seemed to precede the peak of flying insects, insects within samples being most abundant by September and October while flying insects were abundant by October and November.

The moths E. cautella and P. interpunctella appeared to be abundant when temperatures were low and relative humidities were high. High temperatures seemed to favour the building up of populations of T. castaneum

Free fatty acids and peroxide levels of groundnut samples were determined and used as parameters for assessing the extent of damage of nuts by pests; these values correlated with insect infestation in most. cases.

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