THE ASCOSPORE AND OTHER FUNGI 251 



BLACK ROT OF GRAPES 



The Black Rot of grapes is one of the most destructive 

 plant diseases. It often causes the loss of a large part of 

 the crop in many vineyard regions and is generally recognized 

 as a dangerous enemy. The disease is caused by a fungus 

 that passes the winter in mummied grapes and is believed 

 to start in spring from ascospores developed in them. It 

 appears in spring or early summer on young leaves and 

 branches, producing a brown discoloration. Later it shows 

 on the green grapes as brownish spots that spread over 

 the whole surface, finally producing a blackened fruit that 

 is appropriately described as affected by Black Rot. 



On the surf ace of these diseased grapes enormous numbers 

 of summer spores are developed. These are scattered 

 through the vineyard by wind and rain. Whenever one 

 rests upon a moist grape, it is likely to start a new disease 

 spot. In this way the disease may spread very rapidly 

 and cause great loss. 



Clean culture and the destruction of dried grapes that 

 carry the fungus through the winter are desirable preven- 

 tive measures. Spraying with Bordeaux mixture has re- 

 peatedly been shown to be an efficient remedy. 



COTTON WILT 



Among the numerous enemies of cotton that have be- 

 come seriously destructive during recent years, the Wilt 

 Disease is especially notable. It occurs over a large part 

 of the cotton-growing region in the Southern states. The 

 affected plants are commonly stunted in their growth for 

 some time before they finally wilt as if from lack of water. 

 This is in fact the case, because the channels through 



