Florida Agricultural Experiment Station


to other details full benefit from its use cannot be obtained. It
is probable that there are but few cotton lands in Florida on which
potash can be safely omitted, and 3 or 4 percent of the fertilizer
used on cotton should consist of this element.


 SORESHIN
 The soreshin disease is caused by the fungus Corticium vagum
 solani Burt, the mycelial stage of which is known as Rhizoctonia
 solani Kuhn; and the disease is still often spoken of as the Rhi-
 zoctonia disease. The soreshin disease is the most common cause
 of poor stands of cotton in Florida. Its injuries are ordinarily at-
 tributed to cold, damp weather in the spring, but if it were not for
 the presence of the causal fungus in the soil, the young cotton
 stems and roots would remain white and healthy except for oc-
 casional plants attacked by some other fungus. The fungus, how-
 ever, is extremely widespread throughout the United States, and
 foreign countries as well, and attacks a great many plants
 other than cotton. On account of the nature of injury it is
 impossible to make estimates of loss, but poor stands mean low
 yields per acre.
 The fungus causing soreshin lives in the soil from year to
year on decaying plant material and under favorable conditions
is capable of attacking a kreat many different kinds of plants
when they are young. The pathogenicity of the fungus is en-
tirely dependent on the temperature of the soil, and after the
soil has become thoroughly warmed the fungus is incapable of
attacking the plants, but at temperatures below about 80F. the
disease attacks young plants, the extent of injury increasing to-
ward the lower temperatures. If favorable temperatures are
constantly maintained 100 percent killing of the cotton seedlings
is common, but comparatively brief periods of exposure to unfav-
orable temperatures, that is, high temperatures, are sufficient to
reduce greatly the severity of the disease. This is the reason that
greatest injury from the soreshin disease occurs during damp,
cool, cloudy periods during which the soil maintains uniformly
low temperatures. Since, on account of the boll weevil, it is nec-
essary to plant cotton earlier than it would be ordinarily, the
prevalence of this disease has increased. The soreshin fungus
is also capable of rotting cotton bolls, but the rot occurs rather
infrequently and only on bolls close to or in contact with the soil.