Staining methods for detecting weevil infestation in grain /

Abstract

The eggs and immature stages of the rice weevil (Sitophilue oryga (L») and the granary weevil (S. granarius (L»))» hidden within the kernels of vriieat, com, or other grain, are invisible to the naked eye and cannot be detected by ordinary inspection methods. Grains that grade No« 1 nay actually have a hi^ percentage of infested kernels. If this grain it used for milling, the different stages of the weevils* together with tha cast skins and excrensnt, will be ground up in the milling process and the finished flour or meal will thus be contaminated with the fragmants* In order that the miller may produce a pure product he must know the condition of the grain he is grinding. So far as the miller is concerned, it matters little whether the infestation in the grain is alive or dead, or what stages are present, since any stages of the weevils from egg to adult, -w^iether living or dead, will contaminate the finished product. A miller may therefore buy a No, 1 grade grain, which apparently is free of infestation because of fumigation and cleaning methods applied prior to its arrival at his mill, but which may, nevertheless, be heavily infested with immature stages of weevil hidden within the kernels. A simple, practical, and inexpensive method has been devised by the author for detecting this hidden infestation in grain. It consists of treating samples of the grain with a dye which stains the egg-plugs and weevil punctures. In depositing her egg the female weevil first drills a tiny cavity into the surface of the grain kernel. After depositing her egg in this cavity she seals the opening with a gelatinous secretion, niiich hardens and serves as a protective plug. This plug remains on the grain throughout the development of the immature stages, and, unless removed by the emerging adult weevil, will remain on the infested grain indefinitely. Therefore, no matter what stages of the weevils may be present, any infested kernel can be easily detected by the use of a dye that has an affinity for the egg-plugs. There are two dyes iriiich may be used in testing for weevil infes-tation in grain. Because of its decided advantages, the author prefers the acid fuchsin dye. It is prepared with the following ingredients: