Excerpts from the report: The primary objective of this study was to compare the effectiveness of malathion and synergized pyrethrum emulsions and a diatomaceous earth (inert dust) as protectants of shelled corn against insect attack. In general, three phases of testing are required to develop a protective treatment for grain; namely, (1) a preliminary laboratory evaluation of candidate insecticidal materials, (2) an intermediate, small-bin evaluation, and (3) full-scale bin, elevator, and warehouse tests. Only the materials and dosages that demonstrate effective possibilities in the small-bin tests are field tested on a large scale. In this test, two dosage levels of malathion and single dosages of a synergized pyrethrum and a diatomaceous earth were tested, using the small-bin method intermediate between the laboratory-type, small-jar tests and the full- scale field applications.