Efficacy of neem oil and neemazal against the larger grain borer, prostephanus truncates (Horn) in stored maize

Abstract

The biological activity of neem oil and Neemazal on adult and immature stages of the larger grain borer Prostephanus truncatus, as well as on its F1 progeny was assessed in stored maize in the laboratory. Repellency and persistency effects of the treatments in grain to the insect, as well
as the effect of the treatments on grain damage, were also determined. Neemazal was more toxic to P. truncatus than neem oil. The highest dosage of 0.8ml/200g grain killed 100% adult P. truncatus after 72 h exposure but the same dosage of neem oil resulted in 70% mortality after 96h. The products also caused significant (p<0.05) mortality in P. truncatus eggs and larvae. Neemazal provided greater protection of maize grains with no noticeable boreholes on grains treated with 0.6 and 0.8ml/200 g grain. All treatments repelled less than 50% P. truncatus adults. Activity of the two products significantly (p<0.05) declined in treated grain after 24h of storage following treatment. Neemazal offered greater protection against both the immature stages and adults of P. truncatus in stored maize.