v.. V. 1. 587. 



GRAPE-SPRAYING EXPERIMENTS IN 

 MICHIGAN IN ll>09. 



INTRODUCTION. 



Black-rot of the iiiajje, which is caused l)y the fungus Gtdgnardia 

 hidwellii (Ell.) V. & 11., is Avithout doubt the most destructive 

 fungous disease of grapes in the eastern United States. Its first 

 appearance in the spring is usually in the form of brown spots on 

 the leaves, ui)on which a number of small black pustules niay soon 

 be seen. These contain one kind of spores by means of Avhich the 

 fungus is i-eproduccd, sometimes called summer sjoores. These minute 

 rounded bodies are scattered chiefly by wind and rain. When under 

 favorable conditions one alights on the leaves, 5^oung shoots, stems 

 of bunches of grai^cs, or the berries themselves, it sends out a tube 

 which may penetrate and destroy the tissue. The result of the 

 infection of the berries is usually first evident as a whitish spot on 

 the surface. This is soon surrounded by a light-brown area, which 

 gets darker as the disease ^jrogresses. The grape meanwhile shrivels 

 up and finally becomes dark and mummied and covered with the 

 black pustules containing the spores. 



There is also a form of spores called winter spores, which grow 

 in black pustules similar to those described above. These are very 

 common on the ohl mummied grapes in the spring and summer, and 

 are a very efficient means of reproducing and distributing the fun- 

 gus. In favorabk' weather the disease spreads rapidly and does an 

 immense amount of damage. In a hot season with frequent rains 

 it is not uncommon to see the entire crop of a heavily laden vine- 

 yard totally destroyed or so badly damaged that the grapes would 

 not i)ay for the labor involved in harvesting. 



During the early years of the industry in the principal grape- 

 growing region of Michigan, located around Lawton and Pa^v Paw, 

 very little was known of black-rot. The grape districts of New 

 Jersey. Pennsylvania. New York, and Ohio all suffered severely at 

 times during this period from this destructive parasite, but the Mich- 

 igan vineyards w^ere comparatively free from it. As the farmers 

 learned that this locality was better adapted to the raising of grapes 

 than to general farming more vineyards were set until grape growing 

 became the principal industry. The acreage of grapes increased and 



[Clr. 65] 



3 



