246 



bringing about the death of the parts attacked. Cutting across the main 

 root near the crown of the plant shows an abnormal yellow color in the 

 woody parts. 



First reports of this disease in Illinois were made in 1921 by An- 

 derson, who found it serious locally. In 1922 it was so severe where 

 seen, as to cause a general loss of 25 per cent of the crop. In 1923 wilt 

 appeared less severe but was thought to have resulted in about a 20 per 

 cent crop reduction. 



It is now known to occur in 21 counties, widely distributed, as indi- 

 cated on Map 106, and representative to a marked degree of the regions 

 in which melon culture is important, thus suggesting that wilt is wide- 

 spread and common in Illinois. 



Its seriousness may be illustrated by a summary of some of the 

 1923 field notes. In Cass county in a 10-acre field of melons, largely 

 Irish Gray, more than 90 per cent of the vines of that variety were dead 

 by September first. In a two-acre field in Mason county more than 50 

 per cent of the vines were dead by August 31. In Henderson county 

 some 20 acres devoted to melons, especially Irish Gray and Excel, 

 showed 80 to 90 per cent of the vines dead before the melons ripened. 

 It is reported that in White county, where there is a large melon acreage, 

 the wilt completely destroys the crop in many individual fields. In John- 

 son county 50 to 100 per cent loss is reported. In Gallatin county 5 to 

 15 per cent loss commonly occurs, but in a 7-acre field of Tom Watson 

 melons 85 per cent of the plants were dead by August G. In Lawrence 

 county the variety Excel suflfered to the extent of 20 to GO per cent. 

 These notes, while not representing the condition of infection in the 

 average field, are certainty illustrative of the damage this disease can 

 cause. 



To escape these tremendous losses, it is necessary to understand 

 that the fungus which causes the disease inhabits the soil and that when 

 soil has once become infected it may remain so for years, producing 

 the disease in every watermelon crop planted on the land. If water- 

 melons are cropped on the same land year after year it is to be expected 

 that within a few years it will be impossible to grow melons profitably 

 on that land. This soil infection is commonly noticed by growers, and 

 there is much doubt whether land once infected with wilt can ever be 

 profitably used again for melons. One grower reports severe wilt on 

 land not cropped to melons for eleven years ; another reports bad wilt 

 after 23 years ; another, who ])ractices a 3-year rotation, finds he has 

 large losses ; and another, after an 8-year rotation, found his crop severely 

 diseased. Certainly it is not safe to crop wilt-infected land to melons 

 short of a 10-year lapse in such cropping. Additional* care must be 

 taken to grow crops which will not be likely to spread the infection to 

 the manure heap, and thence to all jxirts of the farm. 



The ultimate solution of the jiroblcm of wilt control will iircibably 

 be found in the development of wilt-resistant varieties. This task has 

 been undertaken and is already yielding promising results. 



