134 Diseases of Economic Plants 



Powdery-mildew (Sphoerotheca humuli (DC.) Burr.). — 

 This mildew may he recognized by the characters usually 

 pertaining to the powdery-mildews. (See grape.) 



Upon the strawberry it induces curled, in-rolled leaves, 

 and the white mycelium is found upon their lower surfaces. 



The disease is not usually troublesome. 



Botrytis-rot ^^^ {Botrytis sp.). — This rot, though prevalent 

 in the fiekl, occasions serious loss only on l^erries which are 

 shipped over long hauls. The rotten spot is dry, tan-colored, 

 and finally covered with downy spore clusters. Careful 

 sorting to avoid shipping of infected berries is necessary. 

 Infected fruit that is sorted out should be buried with lime. 



Leak ^''^ {Rhizopus nigricans Ehr.). — Berries often decay 

 in shipment, the juices leaking out from the bottoms of the 

 boxes. The berries sink to a feltlike layer covered by mold 

 and its black sporangia. This rot causes millions of dollars 

 loss annually. Only sound berries should be offered for ship- 

 ment. 



Miyior diseases 



Leaf-blight ^-'^ due to Aposphseria; Leaf-spot due to 

 Ascochyta; Fruit rots due to Sphgeronemella,^^^ Patellina,^" 

 and occasionally to the black-rot fungus, Physalospora/^^ 

 do some injury. 



