Bulletin 214, Cotton Diseases in Florida


cultural methods are very important in lessening the damage from
various cotton diseases. Furthermore, many of the parasites
causing boll diseases are unable to attack uninjured bolls. There-
fore, the loss resulting from these diseases can be reduced by con-
trolling the boll weevil, and thus lessening the number of punc-
tured bolls.
 By rotating cotton with other crops, as is recommended for
maintaining the soil in the best condition, many diseases caused
by parasites that live in the soil are reduced. Most cotton para-
sites are limited to cotton alone, consequently, the growing of
crops other than cotton deprives them of their food with the result
that they die out. Long rotation of cotton with resistant crops
alone are recommended for the control of root-knot.

 WILT OR "BLACK ROOT"
 Cotton wilt or "black root," as it is commonly called, is caused
by a soil-borne fungus, Fusarium vasinfectvm Atk. The disease
is widespread over the entire cotton belt, being more or less re-
stricted to the lighter soil types, and is especially severe where
the nematode or root-knot disease occurs. The losses attributed
to this disease vary somewhat from year to year, but for the en-
tire United States they amount to approximately 400,000 bales
annually. It is one of the worst diseases that the Florida cotton
farmer has to combat, but fortunately it is rather localized in its
distribution, and is rather easy to control by the use of resistant
varieties. It is very difficult to estimate the losses caused by wilt
in Florida on account of the lack of uniformity in its distribution
but fields have been observed in west Florida abandoned on ac-
count of this disease and in certain areas it is not uncommon to
find 50 percent of the plants killed. Cotton may be attacked at
any time after it is well out of the ground and the losses in young
cotton are often very serious.
 The fungus lives in the soil on decaying cotton stalks, and
probably on other plant material, and is capable of surviving in
fields planted to crops other than cotton for a number of years,
though it gradually dies out after the culture of cotton has been
discontinued. It may be spread from field to field on the feet of
workmen and animals, on cultivation implements, and by wind
and rain. After plants are killed by wilt, the fungus forms spores
in great numbers around the bases of the plants. These spores
are extremely small and are borne by-wind and rain to infest