EFFECT OF FUMIGATION UPON HEATING OF GRAIN 
CAUSED BY INSECTS 1 
By E. A. Back, Entomologist in Charge , and R. T. Cotton, Entomologist , Stored 
Product Insect Investigations, Bureau of Entomology , United States Depart¬ 
ment of Agriculture 
The heating of grain in storage is one of the serious problems confronting the 
farmers and grain dealers. A moisture content in wheat of 14.5 per cent has been 
fixed by the Bureau of Agricultural Economics of this department as a line 
between safety and possible danger, so far as the moisture content affects the 
keeping quality of wheat in storage. It is well known that the heating of grain 
may be caused by a high moisture content, and grain dealers have been put to much, 
expense in devising methods of quickly detecting unusual rises of temperature 
in stored grain (by means of electric thermometers, for instance), and in prevent¬ 
ing its continuance by transferring from bin to bin, by mixing lots of grain of 
different moisture content, or by passing the grain through drying machines. 
With heating due to causes other than insect infestation, this paper does not 
deal. 
From the foregoing statements it may be assumed that when wheat shows a 
moisture content of less than 14.5 per cent, it is likely to remain in condition if 
given proper storage. Grain dealers, farmers, and seedsmen are aware, however, 
that seeds containing a lower percentage of moisture may heat badly if they 
become infested with insects. Thus, wheat arriving at the Baltimore grain 
terminals during 1923 was found heating as a result of infestation by the Angou- 
mois grain moth 2 when its moisture content was but 12 per cent. In farmers’ 
bins wheat is very often found heating as a result of attack by the rice 3 and 
granary weevils, 4 while beans, cowpeas, and chick-peas are commonly infested 
by bruchids, and heat badly as a result. 
During the season of 1919-20, G. H. Baston, of the then Bureau of Markets 
and Crop Estimates of this department, recorded ( 15 ) 5 observations made during 
the storage at Buffalo, N. Y., of 15,000,000 bushels of wheat belonging to the 
war-time Grain Corporation. In spite of the fact that this wheat had an average 
moisture content ranging from 11.3 to 12.6 per cent, it was found during the 
winter months that it was in part going out of condition, and it became necessary 
to run the bins to determine the actual state of the grain. Nine hundred and 
seventy-seven bins were transferred and examinations made; of these, 374 were 
in good condition, 396 were “ found to contain a trace of weevil and beetle infes¬ 
tation,” 6 and 207 were found “infested with weevil and beetle.” By taking 
1 Received for publication Apr. 22, 1924—issued November, 1924. 
1 Sitotroga cerealella. 
3 Sitophilus oryza. 
4 Sitophilus gran' rius. 
5 Reference is made by number (italic) to “Literature cited," p. 1116. 
6 By “trace of weevil and beetle" it is meant that specimens of insects were found among the kernels 
which were not apparently damaged, although they may have contained the immature stages; the term 
“weevils" refers primarily to the rice weevil, Sitophilus oryza, and to a lesser extent to the granary weevil, 
Sitophilus granarius; the term “ beetle ” refers to the flour beetle, Tribolium confusum, to the flat grain beetle, 
Cryptolestes pusillus, and to the saw-toothed grain beetle, Oryzaephilus surinamensis, and possibly to 
several others of the smaller grain beetles. 
Journal of Agricultural Research, 
Washington, D. C. 
a 103) 
Vol. XXVIII, No. II 
June 14, 1924 
Key No. K-143 
