232 Diseases of Truck Crops 



Powdery Mildew 

 Caused by Erysiphe dehor acearum D. C. 



Powdery mildew of cucumbers is not a serious 

 trouble, since it usually attacks plants which have 

 somewhat passed their usefulness. Like all powdery 

 mildews, the causative fungus grows on the surface 

 of the leaf, giving it a white mealy appearance. 

 From the mycelium are produced erect threads which 

 bear the summer spores of the fungus. According 

 to Humphrey, 1 the ascus or winter stage appears as 

 minute dark-brown rounded capsules enclosing a 

 group of spore sacs within which are formed the 

 ascospores. 



Anthracnose (fig. 40 h), see Watermelon, p. 240. 



Root Knot, see Squash, p. 237. 



Spraying Cantaloupes and Cucumbers 



Cantaloupes and cucumbers cannot always be 

 grown profitably unless the crops are sprayed. It is 

 fortunate that most of the foliage and fruit diseases 

 may be kept in check by spraying with Bordeaux 

 mixture. The work of Orton 2 and others has shown 

 that not only does spraying control the various dis- 

 eases, but viewed from the point of view of dollars 

 and cents it undoubtably pays. 



1 Humphrey, J. E., Massachusetts Agr. Expt. Sta. loth Ann. 

 Rept.: 225-226, 1892. , 



2 Orton, W. A., U. S. Dep t. of Agr. Farm. Bui. 231: 5-24, 1905. 



