Family Compositae 145 



riris disease is induced by two species of Septoria 

 ftingi. The symptoms produced by both are so 

 neaxly alike that it is difficult to distinguish one from 

 the other, except by microscopic examination. Pale 

 brown discolored spots appear on the older leaves 

 with numerous black pyciiidia in the center. The 

 disease is of little economic importance, as it usually 

 occurs late in the season, on plants which have nearly 

 passed their usefulness. The Boston variety is con- 

 sidered resistant, while the Salamander and the 

 Wonderful are more susceptible to leaf spot. 



Shot Hole 



Caused by Marsonia perforans E. and E. 



The disease is of little economic importance. Af- 

 fected leaves are covered with dry spots which drop 

 out, leaving irregular perforations. Along the border 

 of these holes, the causative fungus may be found 

 abundantly fruiting. The disease attacks the mid- 

 ribs of the leaves as well as the stem of the plants. 

 It seems to be more prevalent under conditions of 

 surface irrigation. With sub-irrigation, on the other 

 hand, it is not found to cause any damage. 



Cercospora Leaf Spot 



Caused by Cercospora lactuccB Stev. 



This disease is as yet of no importance in the 



United States. The trouble occurs in Porto Rico, 

 10 



