The experiments were carried out in the laboratory at 26 ±2°C and 60
±5% RN to evaluate the bioactivity of certain plant extracts against three insect
species infesting stored maize grains. i.e. the rice weevil Sitophilus oryzae (L.),
the red flour beetle Tribolium castaneum (Herbst) and the lesser grain borer
Rhizopertha dominica (F). The plant extracts were the acetone and petroleum
ether of Poinciana seeds Delonix regia, Cinnamon strip bark Cinnamomum
zeylanicum, Colves flowering buds Syzygium aromatcum, Mustrad seeds
Brassica alba and Radish seeds Raphanus sativus).
The results, revealed that, the adults of T. castaneum were the least
susceptible to the various tested plant extracts followed by R. dominica and S.
oryzae adults, which were the most sensitive. It was also apparent that, the
reduction in F1 progeny of T castaneum was much higher than mortality at all
tested concentrations of the plant extracts.
Results showed also that the repellency effect of the tested plant extracts
varied from one plant to another. Data revealed that S. oryzae adults showed the
highest repellency values with the various plant extracts at various intervals in
comparison to the two other insect species (T castaneum and R. dominica).
While the R. dominica- adults were the lowest response repellency values.
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