Fusarium in Tuber Rot and Wilt of Potato 17 



On March 15 the following notes were taken. Series A: plant 1, 

 slight curling of leaves; 2, apparently sound; 3, curling of leaves; 

 4, curling of leaves. Series B: plant 1, drooping leaves; 2, lower 

 leaves drooping, upper leaves drying; 3, apparently sound; 4, 

 apparently sound. Series C: plant i, apparently sound; 2, some 

 wilting; 3, some wilting; 4, some wilting. Series D: plants 1,2, 

 and 3 apparently sound; 4, wilting. By March 21 the plants 



A B 



Fig. 3. — Wilt produced in laboratory with Fusarium oxysporum, and control 

 plant; A, control, Early Ohio variety; B, wilting of lower leaves and curling of upper 

 leaves, 4 days after inoculation, Early Ohio variety. 



infected with F. oxysporum showed a pronounced folding upward 

 of leaves on the midrib, wilting and rolling on the margins of the 

 leaves, the folding being most pronounced in the tips of the plants. 

 The plants affected least showed discoloration on the margins, 

 which at times was of a yellowish tint, at times purplish to violet. 

 The leaves of plants most severely affected showed a yellowing and 

 burning of the leaf margins. One plant, inoculated with F. oxyspo- 

 rum, developed a pronounced rosette, but overcame this later, grow- 

 ing into quite a normal plant (figs. 4 and 5). These symptoms 

 remind one forcibly of certain symptoms of the leaf-roll disease which 

 has received so much attention, and which has been made the subject 



