VEGETABLE AND FIELD CROPS 309 



per cent of plants between half-grown and maturity. In 

 1905 the disease was probably more general than ever 

 before, completely ruining many fields in southern Califor- 

 nia. The plants usually reach considerable size, blos- 

 som, and set fruit before showing the disease, which first 

 appears in the field on single plants, which are generally 

 sickly looking, and of unhealthy color, followed by 

 symptoms of wilt. The leaves do no.t blacken or sud- 

 denly die, but the whole plant gradually sickens, loses 

 color, wilts, and finally collapses upon the ground. The 

 disease comes on gradually in the field, affecting plants 

 here and there in a very scattering manner. In the worst 

 cases they all die before the summer is over, sometimes 

 quite suddenly at the last ; again, the field goes through in 

 a spotted condition, with plants missing more or less ex- 

 tensively. If a badly affected or dead plant be pulled up, 

 the roots are found to be decayed or destroyed. When first 

 affected, this is not the case ; if a plant is pulled up as soon 

 as it begins to show wilting and fading, the roots look 

 healthy and sound. But if such plants be carefully dug, 

 to avoid breaking off the smaller roots, it will be seen that 

 many of the larger laterals are decayed at the ends and are 

 in bad condition. The disease consists of a dry rot of the 

 roots, commencing at the ends and working upward. 



The first symptom is a pale yellowish color of the 

 lower leaves, which soon dry from the tip toward the 

 base without spotting. The veins and woody portion of 

 the stem, if examined in cross section, are darkened, espe- 

 cially upon the side bearing the diseased leaf. The disease 

 progresses from the old leaves to the youngest, resulting 

 eventually in the death of the plant. 



