Cypress (Cupressus macrocarpa) Leaf Powder Modulates Metabolism of Maize Weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Aims: Maize grains are severely damaged by maize weevil Sitophilus zeamais. Exploiting botanicals against synthetic insecticides as a control strategy has gained prominence in recent decades. The aim of the study was to investigate the potential of cypress (Cupressus macrocarpa) to exert some control on S. zeamais.

Methodology: Maize and S. zeamais were collected from Muea market in Buea, Cameroon. The maize was heat sterilized and all debris removed. Sitophilus zeamais was reared for three generations before use. Ten S. zeamais were stored with 100 g of maize and 0 g, 2 g, 5 g, and 10 g of shade-dried cypress leaf powder was added in three replicates. Data was collected weekly for 5 weeks and analysis of variance was done. The study was conducted in a laboratory of the Teaching and Research farm in the University of Buea, Cameroon, in a randomized complete design.

Results: Mortality of S. zeamais was significantly affected (F = 126.67, df = 3, 8, p < .001) by different doses of cypress leaf powder. The mean mortality was 0%, 40.47%, 50.6% and 70.67% for control, 2 g, 5 g and 10 g of cypress leaf powder, respectively. Grain damaged (%) and holed grain were also influenced by cypress leaf powder. The highest grain damaged and holed grain were from the control treatment. A strong positive correlation (r = 0.814, p < .001) was observed between grain damaged and holed grain while a strong negative correlation was observed between mortality and holed grain (r = -0.926, p < .001), and grain damaged (r = -0.913, p < .001).

Conclusion: It is revealed that cypress leaf powder can alter some metabolic activities of S. zeamais, thus it can play a role in an integrated pest management program (IPM) of S. zeamais in maize storage.