LIBRARY 
STATE PLANT BOARP 
Jul7 1948 ET-256 
Ulaited States Department of Agriculture 
Agricultural Research Adminietration 
Bureau of Entomology and Plant Quarantine 
STAINING METHODS FOR DETECTING WEEVIL INFESTATION IN GRAIN 
By J. C. Frankenfeld 
Division of Cereal and Forage Insect Investigationa 
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: 
Acid fuchsin 0.5 gm. 
Glacial acetic acid 50.0 cc. 
Distilled water 950.0 cc. 
Mix the distilled water and glacial acetic acid and then add the acid 
fuchsin which dissolves readily in this solution. Care should be taken 
iJUL 2 2 1948 
