352 Diseases of Truck Crops 



The Organism. F. lycopersici is a soil fun^s 

 whicli may be introduced with infected manure or 

 seedlings. The fungus greatly resembles F. oxy- 

 sponmi. The conidia are hyalin to yellowish, fal- 

 cate, acute. 



Control. Spraying will not control this malady 

 since the parasite lives internally and cannot be 

 reached by external applications. Long rotations 

 in which the land is given a rest from tomatoes are 

 recommended for at least ten years. The selection 

 of resistant varieties may offer a means of conquering 

 this trouble. 



Yellow Blight 



Caused by Fusarium orthoceras App. and Woll.; 

 Fusarium oxysporum Schl. 



This disease is common on tomatoes in the Pacific 

 Northwest. It has been investigated by Humphrey' 

 and found by him to be caused by the two species of 

 Fusaria above mentioned. 



Symptoms. It does not usually manifest itself 

 until late, when the plants are blooming, or even 

 when the fruits are partly formed. At first there is 

 a slight twisting of the entire leaf, accompanied by a 

 purpling of the veins. This is also followed by a 

 rolling inward, and by drooping, but not wilting, of 

 the leaflets and leaves. The foliage then take on 

 glaucous greenish color, the fruit ripen prematvirely, 



" Humphrey, H. B., Washington Agr. Expt. Sta. Bui. 115 : 1-22, 

 1914- 



