246 Diseases of Truck Crops 



infected with Fusarium cucurhitCB, thus making it 

 also sick to squashes. 



Control. Since the disease works in the interior of 

 the plant, it is obvious that sprajTing would be of 

 little help. Rotation of crops is the only practical 

 method of control. It usually takes from two to 

 three years for wilt to establish itself very seriously 

 in the field. Because of this, growers often fail to 

 appreciate its importance tmtil too late. Any 

 possible profits made during the time the crop has 

 been grown in succession on the same land are more 

 than oflEset by the fact that the infected soil is ren- 

 dered sick and tmfit for watermelons for ten years 

 or longer. Watermelon plants suflEering from wilt 

 should never be plowed under, but should be pulled 

 out, dried, and burned. Wilt may be spread by 

 cattle and horses which are allowed to pasture in the 

 sick melon patches, and then brought to healthy 

 fields. Finally a method which promises great re- 

 lief is the development of resistant varieties which 

 are able to grow in sick soils. The United States 

 Department of Agriculture has developed a wilt re- 

 sistant variety named Conqueror. This is a cross 

 between the citron and the Eden. The Conqueror, 

 however, is not as yet popular with the market be- 

 cause of the uncertain qualities of the citron which it 

 still has. Resistant varieties may no doubt be ob- 

 tained by selection with the best commercial vari- 

 eties. For methods of selection for resistance see 



P- 374- 

 Root ICnot, see Nematode, p. 49. 



