The insecticidal potentials of acetone extracts of fruits from three plants (Piper guineense, Zingiber officinale and Azadirachta indica) to preserve stored Cowpea, Vigna unguiculata against infestation by Callosobruchus maculatus was investigated. Laboratory bioassays for adult mortality, oviposition deterrence, suppression of adult emergence and antifeedant deterrence were conducted using acetone extracts prepared by measuring 0.1, 0.5, 1.0 and 2.0g of ground plant powder into 5cm3 of acetone. These concentrations translated into 1% (w/v), 5% (w/v), 10% (w/v) and 20% (w/v) of extract treatment respectively. The filtrates were then used to treat cowpea seeds in Kilner jars. Ten pairs of sexed bean weevils were introduced into each treatment jar including the control and five replicates were set for each treatment. Data obtained were subjected to descriptive statistics of mean, standard deviation, percentages and bar graphs. Means were compared and separated using Analysis of Variance (ANOVA) and Least Significance Difference (LSD) respectively at P < 0.05. The results showed that all extracts at all doses significantly (P>0.05) produced high adult mortality ranging between 62.5-100% after seven days of treatment. Oviposition was inhibited significantly (P>0.05) in all treatments ranging between 68.3-100%, adult emergence was completely and significantly (P>0.05) inhibited at higher doses of P. guineense and Z. officinale while the antifeedant index was significant (P>0.05) in all treatment ranging from 51.4-100%. The study revealed that extracts of these plant's fruits were efficient in the control of C. maculatus in stored cowpea and their usage as protectants is recommended as an efficient alternative to the use of hazardous synthetic insecticides in the storage of cowpea seeds.
Key words: Insecticidal, Mortality, Oviposition, Emergence, Antifeedant
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