Postharvest Insect Control with Inert Dusts

Abstract

Inert dusts such as; clay, sand, rock phosphate, ashes, diatomaceous earth, and synthetic silica, have been used as insecticides for thousands of years by aboriginal peoples in North America and Africa and are also used in modern grain storage facilities (1). Modern day research on inert dusts as a stored-grain protectant began in the 1920's (1, 2, 3, 4). Some inert dusts work by damaging the insect cuticle, causing death by dessication. Other dusts such as clay, sand and ashes are used at higher doses (above 10%, w/w), and they work by providing a physical barrier against insects (3). The main advantage of inert dusts is their lowmammalian toxicity. In Canada and the USA, diatomaceous earth is registered as an animal feed additive and silicon dioxide is registered as a human food additive (1). Also inert dusts are effective for long durations and they do not affect end use quality (2). Their main disadvantages are that they are dusty to apply, do not work at high relative humidities and impede the flow of grain (5, 6).