Seasonal Changes in Field-to-storage Insect-pests of Maize and Implications for Their Control in South-Western Cameroon

Aims: To identity and assess the seasonal population dynamics of field-to-store insect-pests of maize at various harvesting dates in South-western Cameroon.

Methodology: Maize was planted mid-monthly during the rainy season months of 2014 and 2015 in 16 plots. At physiological maturity 2 cobs per plot were harvested weekly. The harvesting was for four weeks for maize planted from March to May and five weeks for those planted from August to October. The different insects were assessed from maize cobs with intact husk at harvest, during de-husking after one month drying and subsequently during incubation at two and four weeks. Insect-pests from intact and bird-induced damaged cobs at harvest were also compared.

Results: The results showed that Cryptolestes ferrugineus, Sitophilus zeamais, Ephestia cautella and Sitotroga cerealella were the major field-to-store insect-pests at harvest. C. ferrugineus was present during all the months of harvest, S. zeamais only in cobs harvested during the dry season months of November, December and January while E. cautella and S. cerealella though present throughout the year showed a slight increase during the months of the dry season. As concerns harvest dates, the longer maize stayed in the field post physiological maturity, the higher the population of S. zeamais and C. ferrugineus while E. cautella and S. cerealella did not vary significantly. Cobs damaged by birds had significantly higher numbers of C. ferrugineus and S. zeamais compared to intact maize cobs while E. cautella and S. cerealella did not show any difference between the damaged and intact maize cobs.

Conclusion: Harvesting maize early and separating bird-induced damaged cobs from intact ones can therefore minimize stored insect-pest numbers and grain losses in storage.