Abstract:
Trehalase is an enzyme that breaks down or hydrolyzes trehalose into glucose. In this study, the
impact of ecological zones on the activity of trehalase in Sitophilus zeamais was investigated.
Also, the inhibitory effects of an organophosphate (DDVP) and a botanical (Eugenia aromatica)
on the activities of the enzyme in the insect from selected locations (savannah, rainforest and
mangrove) were studied. Samples of maize grains infested with S. zeamais were obtained from
nine locations across the three ecological zones of Ondo State. The locations sampled were
Mangrove Forest (Ilaje, Okitipupa, Ore), Savannah Forest (Ikare, Akungba) and Rainforest
(Ondo, Akure, Owo, Ifon). Standard Methods were used to assay the enzyme activity and also to
determine the concentration of protein in the samples. The highest S. zeamais trehalase activity
was observed in the extreme ends of the State, Savannah in the northern part (Ikare-
0.728μmol/min/ml) and Mangrove forest in the southern part (Ilaje-0.639μmol/min/ml) while the
lowest activity was observed in Ondo (0.372μmol/min/ml) which is part of the rain forest. As the
concentrations of the inhibitors increased, the spatial distribution of the trehalase inhibition
changes across the zones. The Savannah forest (Ikare) weevils with the highest trehalase activity
were also inhibited the most by the various insecticides. From the first concentration 2.2-
dichlorovinyl dimethyl phosphate (DDVP), starting from the lowest (0.00001%) to the highest
(0.01%), Ikare (Savannah forest) was largely inhibited. Savannah forest has the highest
temperature thereby affecting the activity of the enzyme. The results of this work show the
activities of trehalase enzyme in S. zeamais in the various ecological zones of Ondo State. The
results also show the impacts of inhibitors such as E. aromatica and organophosphate (DDVP)
on the activity of trehalase enzymes in S. zeamais in the three ecological zones of Ondo State.
Eugenia aromatica and organophosphate 2,2-dichlorovinyl dimethylphosphate (DDVP) posses insecticidal properties that can be improved / developed to curb the damaging activities of S.
zeamais in storage.
