Pest problems and the use of pesticides in grain storage in Malaysia

Pest problems and pesticide use in various types of grain storages in Malaysia are reviewed. Paddy and milled rice account for most of the grain stored. Both bag and bulk storage are practiced. Various species of insects (Sitophilus spp., Rhyzopertha dominica, Sitotroga cerlalella) are the main pests of stored paddy, while in milled rice rodents and birds are of major concern in addition to two insects species (Sitophilus oryzae and Tribolium castaneum). Studies revealed losses due to insects estimated at 3-7 percent in paddy and 5-14 percent in milled rice. The main use of pesticides at present, particularly insecticides and fumigants, is in milled rice godowns, horizontal, ventilated buildings of 1200-20000 t capacity. The contact insecticides malathion and lindane are applied as residual sprays and by thermal fogging. For both water-based spraying and fogging, they are diluted to give doses of from 2-5 percent active ingredient, and are applied at rates of 51/100mø and 11/1000mø, respectively. Fumigation under gas-proof sheeting is carried out using phosphine and, to a lesser extent, methyl bromide. It is suggested that more research needs to be done on ways of improving the choice and application of insecticides in bulk paddy and rice godowns, in the context of an integrated pest management program