VEGETABLE AND FIELD CROPS 223 



The cause is a bacillus which gains entrance through 

 wounds, often through ruptures occasioned by excessively 

 rapid growth. 



Spraying with Bordeaux mixture is recommended ; also 

 turning the melons so as to 

 expose all sides to light and 

 air. 



Wilt {Mycosphoerella citrul- 

 lina (Sm.) Gr.). — This wilt 

 seems to be rare, perhaps 

 affecting to serious, extent 

 only greenhouse-grown can- 

 taloupes. It is known upon 

 watermelon in the field. 



Infection is local at the 

 nodes, never at internodes, 

 and seems to originate at the 

 leaf axil, perhaps due to re- 

 tention at that point of the 

 water necessary for germina- 

 tion of the spores. The edges 

 of the infected areas are "oily 

 green " in color, often with 

 resin-colored, gummy exu- 

 date. The older parts are 



either darker and gummy, Fig. 104. — Portions ot muakmelon vine 

 J 1 J u showing pycnidia and perithecia of 



or dry and gray, and bear Mycosph^reUa. AtoDorsey. 

 many brown pycnidia. 



The fungus is not killed by winter or by fumigation with 

 hydrocyanic acid gas. Spraying with Bordeaux mixture 

 after the plants are about half grown, but before the dis- 



