10 STATE HORTICULTURAL SOCIETY. 



Resolved, That we appreciate the efforts of the Agricultural College in pro- 

 viding for the citizens of the state the splendid Short Course in Horticulture, 

 and that we will assist in advertising the course and promoting attendance. 



J. P. MUNSON, Kent County, 

 F. P. SIMMONS, Wayne County, 

 . H. S. NEWTON, Oceana County, 



Committee. 



CONTROLLING THE GRAPE ROT. 



(prof. l. r. taft, agricultural college.) 



Although the disease known as the black rot of the grape did considerable 

 harm in the southwestern part of Michigan some fifteen or twenty years 

 ago, the injury greatly lessened and for ten years very little loss was ex- 

 perienced. During the last two or three years, however, the rot has reap- 

 peared, and in many vineyards located in the Lawton district the crop was 

 practically ruined in 1905 and was even worse in the unsprayed vineyards 

 in 1906 and in 1907. When it reappeared in 1905 it was found in com- 

 paratively few vineyards, but it developed in many others in 1906, and in 

 1907 very few vineyards within ten miles of Lawton escaped. 



This disease is of a fungous nature and developes when in the presence 

 of moisture. This accounts for the comparative immunity from the disease 

 from 1892 to 1903, when the weather during the months of July and August 

 was comparatively dry, and for the injury that has been experienced during 

 the last three years, when the rain-fall in the section referred to was ab- 

 normally large. 



Upon the leaves, the rot produces circular brown spots, generally from 

 one-eighth to one-sixteenth of an inch in diameter. In the middle of the 

 larger spots small black pimples after a time. The spots due to black rot 

 can be readily distinguished from the brown spots caused by mildew, which 

 have angular and irregular outlines. When black rot attacks the fruit 

 the spots can he detected when of the size of a pin head. They are then of 

 an olive green color. The spots quickly enlarge and gradually turn brown 

 until the entire grape has become involved, when they change to a dull 

 black and the grape soon shrivels and takes on a folded and wrinkled ap- 

 pearance. Later in the season, the entire surface becomes broken up into 

 minute pustules, too small to be seen without a pocket lense. Each of these 

 contain a number of sacs in which the spores carry the disease over the 

 winter. 



In the spring these spores escape and coming in contact with water upon 

 the surface of a grape or grape leaf, they germinate, and entering the under- 

 lying tissues, produce a spot of black rot. Soon after these spots appear, 

 numerous summer spores develop upon the surface and serve to spread 

 the disease during the growing season. 



The disease was very troublesome about twentj^ to twenty-five years 

 ago in Missouri, Illinois, Indiana and Ohio, upon varieties of the Concord 

 type, and as this was before much had been learned regarding spraying, 



