11 



The greatest spread of the wilt disease is by the direct growth of 

 the fungus through the soil from diseased to healthy areas. On this 

 account an area considerably^ larger than that on which the plants are 

 wilting should be included in this rotation. 



(2) Removal of diseased plants. — ^Another important source of infec- 

 tion is the diseased jjlants themselves. The fungus produces on the 

 dead stems and roots great numbers of spores, which are carried to 

 other places in a variety of ways. All diseased plants should be 

 pulled and burned as soon as discovered, so as to prevent the disper- 

 sion of the fungus spores which will finally cover them. 



(3) Avoidance of spread by cattle, tools, etc. — The writer's observa- 

 tions in various places in South Carolina during the past two years 

 lead him to believe that cattle grazing in the fields spread the disease. 

 They should not be allowed to pass freely from infected areas to 

 healthy fields, and it would be better not to pasture such infected 

 fields. Tools should be carefully cleaned after cultivating the dis- 

 eased land. To insure complete destruction of the spores of the wilt 

 fungus, such tools should be scoured clean and then washed with a 

 2 per cent solution of formalin or a 5 per cent carbolic acid solution. 



(4) Care of the compost heap. — The fungus is sometimes introduced 

 into the barnj^ard and compost heap, so that the manure becomes a 

 source of general infection to healthy fields. The utmost care should 

 be taken to keej) diseased plants out of the manure, and if there are 

 any indications that such plants have found their way into the 

 manure, or if any new outbreaks of the disease are traced to the use 

 of stable manure, all su.ch- manure and compost should be used on 

 land where cotton will iiever be planted. 



There is no objection to the use of stable manure which does not 

 contain the spores of the cotton-wilt fungus, but experience has shown 

 that in the case of the closely allied watermelon-wilt fungus a l)arn- 

 yard once infected will remain so for many years, and that all manure 

 taken out of it will be likely to spread the disease. The same is 

 probablj' true of the cotton-wilt fungus. 



SELECTION OF RESISTANT RACES. 



The most encouraging results have come from the endeavor of the 

 Department to find a race of cotton which can be grown on the infected 

 lands. There are always some plants in ever}^ field which resist the 

 disea.se to a greater or less extent, and it frequently happens that of 

 two plants in the same hill, equally exposed to infection, one will die 

 and the other live to the end of the season. All degrees of resistance 

 may be found, from plants nearly killed by the wilt disease to those 

 entirely healthy. The latter are comi^arativelj^ uncommon, however. 



Difi'erent races of cotton vary considerablj^ in their susceptibility 

 to the wilt disease. This was shown by an experiment can-i(>d out by 

 the Department on the fai-m of Mr. H. L. Galloway, at Dillon, S. C. 



