4 GRAPE-SPRAYING EXPERIMENTS IN MICHIGAN IN 1909. 



vineyards extended in almost solid blocks for miles. At the same 

 time the fungi parasitic upon this fruit became more Avidely dis- 

 tributed and firmly established. This was the condition about 1905, 

 which was the beginning of a series of wet seasons very favorable for 

 the development of most fungous diseases and especially black-rot. 



In the season of IDOG considerable damage was done in certain 

 parts of the grape district and some of the growers became rather 

 discouraged over the outlook. Some vineyards did not suffer from 

 the disease, while in others the crop was not worth harvesting. A 

 few of the growers endeavored to control the disease by spraying, 

 and in some cases their ett'orts met with partial success. Very little 

 was done, however, toward fighting the disease, as many of the vine- 

 3^ardists were of the opinion that the trouble was only temporary 

 and did not wish to go to the expense of buying machinery and 

 f)reparing to spray for one season. They hoped that the next few 

 seasons would be less favorable for rot and the injury from the 

 disease would cease to be important. Such, however, was not the 

 case. 



The next year, 1907, demonstration work on the control of the 

 disease and spraying experiments to determine the comparative value 

 of various spray mixtures Avere begun by the Bureau of Plant Indus- 

 try of the United States Department of Agriculture. This work 

 was taken up in accordance with an understanding with the State 

 Agricultural Experiment Station at Lansing. It was carried on 

 through the seasons of 1907 and 1908, as reported in a ])revious 

 publication of this Bureau," and continued in 1909 under the innne- 

 diate direction of Dr. C L. Shear, as described in the following 

 pages. 



THE DISEASE IN 1909 AND EXPERIMENTS TO CONTROL IT. 



The weather during the season of 1909 was very favorable for 

 black-rot. Frequent rains with intervals of warm, humid weather 

 furnished excellent conditions for the development and distribution 

 of the spores. The first evidences of the disease on the young growth 

 were noted on June 11, when leaves with the characteristic brown spots 

 bearing the fruiting bodies of the fungus were found. By June 24 

 considerable damage had been done in unsprayed and poorly sprayed 

 vineyards by the rot on the stems of the blossom clusters, peduncles 

 of the flower buds, and calyxes of the unopened fiowers. Whole 

 bunches were destroyed in this way, the fungus causing the buds 

 to shrivel and dry up. (See PI. I, fig. 1, .4.) Thus in some cases a 

 considerable portion of the crop was destroyed before the flowers 

 ojjened, while the properly sprayed fruit was unharmed. (See PI. 



a See " The Coutrol of Black-Rot of the Grape," Bulletin 155, Bureau of Plaut 

 Iiulustry, U. S. Dept. of Agriculture, ii|>. 24-35. 

 ICir. Gfi] 



