Abstract

The present study describes and evaluates a new tool for disinfesting maize grain from weevils using heat from boiling water. In developing countries, rural farmers lose huge amounts of grain due to weevils. Cost of insecticides and resistance of grain weevils to current insecticides are major threats. The grain losses affect the nutritional status and general quality of life of rural communities. Most grain is infested by weevils while in the field before harvest, therefore disinfestation of grain before storage is crucial. The equipment was made from 0.3 mm galvanized sheets and consisted of an inner pot for holding grain, outer pot for boiling water and a two litre metal cup. The most common maize variety grown in Zimbabwe, infested predominantly with Prostephanus truncatus and Sitophilus zeamais was used to evaluate the equipment. Empty maize cobs (after removing the grain) were used as source of heat. The equipment achieved 100% mortality of both species of weevils at 48°C (when grain became hot to the palm) after approximately 30 min of maize exposure to boiling water. There was no loss in grain viability as there was no significant (χ2 =1.4, df=1, p>0.05) difference in germination between treatment and control seeds. The equipment has a number of advantages. There are no health hazards which are normally associated with direct chemical treatment, especially when farmers apply higher doses of insecticide than recommended in an effort to prevent grain losses. Farmers will use empty cobs as source of heat. The equipment can be made locally by the rural farmers. The equipment has the potential to disinfest other small grains.

Key words: Boiling water, maize weevils, heat, economic losses, germination, empty cobs, rural farmers.