June 14, 1924 
Effect of Fumigation 
1115 
given proper storage and kept free of insects. However, when insects are present 
grain has been known to heat when the moisture content is as low as 12 per cent. 
A study of 15,000,000 bushels of wheat by the Bureau of Markets indicated that 
when the moisture content was as low as 11.3 per cent to 12 per cent heating due 
to insect infestation occurred, and resulted in the conclusion, by eliminating 
factors of moisture, damage, and time in storage, that the rising temperatures 
were caused by insect infestation. 
The heating of grain and grain products when insects are present has been 
noted before. The writers have known chick-peas in 240-pound sacks to heat 
as a result of attack by Bruchus quadrimaculatus , the temperature rising to as 
high as 103° F. when the normal temperature was 58° F. Wheat stored in 
farmers’ bins and well infested by Sitophilus oryza and Cryptolestes pusillus was 
found to have developed a temperature as high as 109° F. when the normal 
temperature was 27° F. Wheat in shallow bins or on barn floors and stored in 
piles ranging in depth from 1 to 3 feet was found at times heating if badly in¬ 
fested by the two pests just mentioned and the Angoumois grain moth. It is 
not difficult to find many instances of heating in cereals and such cereal pro¬ 
ducts as animal feeds. 
The cause of heating when insects are present in numbers is not clearly under¬ 
stood. Probably the most prevalent opinion is that heating is due to fermenta¬ 
tion started by the attraction of moisture to the faeces of the insects. Others 
have given as the cause the mechanical friction due to the insects’ feeding. It is 
known that the honeybee cluster in winter can develop by muscular activity not 
unlike shivering a temperature in the hive of 86°-95° F. when the normal tempera¬ 
ture is but 32° F. Grain dealers claim that insects do congregate in large num¬ 
bers in spots in grain in elevators and that such “balls of insects” are responsible 
for starting grain heating. As many as 1,500 Carthartus cassiae beetles have 
been recorded in 1 pound of bran heating at a temperature of 95° F. The writers 
estimated one 240-pound sack of chick-peas with a temperature of 102° F. to 
contain 3,550,960 Bruchids in various stages of development; the sacks not heat¬ 
ing, and having a normal temperature of 58° F., showed no infestation. It is 
undoubtedly true that when grain heats badly as a result of insect infestation the 
insects are present in great abundance. 
The fumigation of grain, heating as a result of insect infestation, with either 
carbon disulphid or hydrocyanic-acid gas brings about a fall in the temperature 
of grain to normal. This was found true in the fumigation of one hundred and 
forty thousand 240-pound sacks of chick-peas stored in six warehouses and con¬ 
taining hundreds of heating sacks. It was also found true in the fumigation of 
heating wheat in farmers’ bins. 
The destruction of heat in grain during winter is of great importance, particu¬ 
larly on the farm. In ordinary storage heating seeds radiate sufficient heat to 
raise appreciably the temperature in the spaces between the sacks in the case of 
sacked seeds. The temperature, which was 58° F. between uninfested sacks of 
chick-peas, was raised to as high as 70° to 78° F. between infested and heating 
sacks, with the result that the Bruchids, dormant at 58° F., were able to multiply 
and actively spread the infestation from the infested and heating sacks. The 
activity of pests in stored corn and wheat is in like manner made possible by 
heating. Heating permits feeding and reproduction to progress even in the dead 
of winter. Fumigation does what cold weather will not do; it kills the heat and 
reduces the temperature of the seeds to normal and thus prevents progressive 
destruction. 
Unless it can be proved that bacteria, molds, or other agencies causing heat are 
killed by fumigation with hydrocyanic-acid gas or carbon disulphid, the writers 
conclude that the activity of certain stored-product pests is directly responsible 
for the development of heat in grain in certain instances and that fumigation will 
kill such heat and permit the grain to return to normal temperature. 
96462—24t-5 
