The Botrytis Blight of Tulips 



325 



color changes to a whitish 

 gray with a brownish tinge, 

 and a translucent or water- 

 soaked area appears about 

 the margin. At this stage 

 the margins of the lesions 

 are quite definite (fig. 24). 

 Toward the center abundant 

 conidiophores are often pro- 

 duced. Under favorable 

 conditions the lesions enlarge 

 still farther, coalesce, and 

 frequently involve the entire 

 leaf. If a lesion develops 

 toward the base of a leaf, 

 it may cause the leaf to 

 break over. When an infec- 

 tion takes place on the mar- 

 gin of the leaf near the tip, 

 there results the character- 

 istic appearance shown in 

 figure 26. This wrinkling 

 and bending of the leaf to 

 one side is due to the more 

 rapid growth of the healthy 

 tissue opposite the lesion. 

 (Klebahn, 1905:4). 



Both young and old lesions 

 are found on the same leaf 

 showing that infections take 

 place continuously (fig. 25). 

 The outer sheathing leaf is 

 likely to be attacked before 

 the others, probably being 

 infected as it emerges from 

 the bulb. It bends down- 

 ward and usually is abun- 

 dantly covered with conidio- 

 phores (fig. 27). 



Fig. 27. a diseased plant 



Showing the outer sheathing leaf infected by con- 

 tact with a lesion at the tip of the bulb. Note the 

 abundance of conidiophores which give rise to 

 inoculum for secondary infections. Natural size 



