329 



Black Rot 

 Caused by Guignardia bidzvcllii (Ell.) V. & R. 



Black rot is the most important grape disease in Illinois. While it 

 attacks all above-ground parts of the vine, it is most commonly seen as 

 a fruit rot and leaf spot. 



On the fruit it first appears as a small white spot, which is soon sur- 

 rounded by a brown ring. The fruit beneath the spot becomes rotten, 

 and small black dots appear upon the surface of the spot. Eventually 

 the entire fruit rots and shrivels to a small, dark mummy. The black- 

 rot leaf-spot appears as a brown, more or less circular spot with a darker 

 margin. In late summer it bears minute black dots on its surface. Stem 

 lesions are charaterized by a dead brown area over which are scattered 

 tiny black dots. 



The history of thjs disease is extensive. It is reported to have been 

 present in destructive amounts in Madison county as early as 1861, and 

 references are made in the Transactions of the Illinois Horticultural So- 

 ciety to a grape disease, probably black rot, which appeared from time 

 to time in Champaign, Hancock, and Madison counties. 



Its present known occurrence in the state is shown on Map 80. The 

 63 counties are so distributed as to indicate that it has a state-wide distri- 

 bution. 



Control is secured in this and other diseases of grapes by the care- 

 ful and thorough application of sprays. 



DowNv Mildew 



Caused by Plasmopara vlticola B. & C. 



Downy mildew is probably second in seriousness among grape dis- 

 eases occurring in Illinois. It is especially a leaf disease, but also at- 

 tacks young stems, fruit, and leaf-stems. On the leaves it appears as 

 white mildewed spots on the lower surface. The leaves first take on a 

 slightly water-soaked appearance where the mildew occurs, and as the 

 spots enlarge they curl ujiward and inward and are eventually killed. 

 Disea.sed flowers do not set fruit ; and fruit, when attacked, either shells 

 off from the vine or dies and becomes mummified. 



The history of this disease in Illinois dates back to 1882, when it 

 was collected by A. B. Seymour at Fall Creek, Adams county. A later 

 collection was made by G. P. Clinton at Urbana in 18!)2, and Burrill re- 

 cords its occurrence in Chami)aign county in 1912 and 1913. 



Its present known distribution in the .state is shown on Map 81. Its 

 occurrence has been demonstrated in 30 counties, with a very irregular 

 distribution suggesting a wide range of occurrence for the disease. 



Control is accomplished through the usual sprays. 



