144 Diseases of Truck Crops 



When the plants are fairly rotted, there appear on 

 the cottony mycelial growth mentioned above, black 

 bodies, or sclerotia, which vary in size from a pin- 

 head to a grain of com. The three definite symptoms 

 of the disease may be summarized: (i) drooping, (2) 

 cottony-like mycelial growth on the under surface of 

 the affected leaves, (3) the appearance of sclerotia 

 (fig. 23 c). The latter help to carry over the fvmgus 

 during the winter. After the sclerotia have been in 

 the soil over winter, they germinate in the following 

 spring by sending out small mushroom-like fruiting 

 bodies known as apothecia (fig. 23 a). The latter 

 contain small sacs or asci which bear the spores (fig. 

 23 b and d). 



Control. The work of Stevens ' seems to show that 

 lettuce drop may be controlled by the following 

 method : The field is inspected as often as possible 

 during the season. Every plant which shows indica- 

 tions of disease is pulled out and burned and the 

 place where it grew is drenched with a solution of ^one 

 pound of bluestone dissolved in seven gallons of water. 

 If these directions are carried out for three years the 

 disease wiU be controlled. The simplicity of the 

 method should make it appeal to truckers and gar- 

 deners. 



Leaf Spot 



Caused by Septoria lactuccB Pass, and Septoria 

 consimilis E. and M. 



» Stevens, F. L., North Carolina Agr. Expt. Sta. Bui. 217 : 7-21, 

 1917. 



