Treatment of Cotton Seed 
41 
GENERAL CONCLUSIONS 
Consideration of the experiments described above leads directly to the 
conclusion that the practical and complete control of cotton anthracnose 
in its seed-borne aspects can be obtained by the use of dry heat. The 
water content of the seeds which are to be heated is a factor of primary im¬ 
portance in determining the essential details of treatment. Control cannot 
be accomplished by the use of seed containing an amount of moisture 
normal to ordinary storage conditions, for dry heat at temperatures ef¬ 
fective in killing the anthracnose fungus carried by such seed either com¬ 
pletely destroys is viability or seriously reduces its germination. Air dry 
seed subjected to dry heat temperatures of 80, 90, 95 and 100° C. succumb 
before the anthracnose fungus is killed and at temperatures of 70° or less 
the vitality of the anthracnose fungus in not destroyed. However, after 
the moisture content of cotton seed has been sufficiently reduced by use of 
relatively low temperatures for appropriate periods of time, they may safely 
be tieated at temperatures sufficiently high to prevent subsequent develop¬ 
ment of anthracnose on the seedlings. The vitality of the spores and 
mycelium of the anthracnose fungus carried on diseased cotton seed can be 
destroyed by the application of dry heat at temperatures of 95° C. for 12 
hours or 100° C. for 6 hours. Temperatures of 80° for 72 hours, and 90° 
for 24 hours, accomplish the same result in all but a fraction of 1 per cent of 
the seeds, and it appears that prolonging the treatment at 80° and 90° to 
96 and 48 hours respectively should destroy the seed-borne fungus in all 
the seeds. When cotton seed have been predried at proper temperatures for 
suitable periods of time, the application of dry heat at 80° for 72 hours, 
90° for 24 hours, or 95° for 12 hours, causes little or no reduction in 
percentage of germination. 100° C. for 6 hours causes a very considerable 
diminution in percentage of germination; however, the number of seeds 
which survive the treatment is sufficiently great to provide for an ample 
stand in the field. 
The anthracnose fungus carried by a small proportion of the seeds is 
much more resistant than that carried by the majority of the seeds. 
Although 14 hours of heating at 90° reduced the anthracnose to 2 per cent, 
the fungus still survived in a small percentage of the seeds in 2 out of 8 
tests in which heating continued for 18 hours and in 1 out of 9 tests in 
which heating lasted 24 hours. It may be that in the few seeds in which 
the fungus survived the relatively long periods of heating, the hyphse of 
the fungus had penetrated deeply within the embryo of the seed and its 
protoplasm was by reason of its position embedded within other living tis¬ 
sue protected from the extreme desiccating and coagulating effects of 
the heat. 
Dry heat treatment of cotton seed has certain obvious advantages over 
any method previously described for control of seed-borne anthracnose. 
It destroys all of the anthracnose fungus carried by diseased seed while 
chemical disinfectants and corrosives are only partially effective at best. 
It may be used in a much wider range of effective temperatures (80 to 
100° C.) than is possible with the hot water method, and the period of 
treatment at any temperature within the effective range may be greatly 
