86 THE GRAPES OF XEW YORK. 



Chautauqua district. The grape-vine fidia, or root-worm, one of the worst 

 of the insect pests of the grape, is not yet destructive in this region. The 

 grape leaf-hopper and the grape-vine flea-beetle are possibly the worst of 

 the insects infesting the grapes about these lakes. 



But fungi are more troublesome than in the Chautauqua district; 

 probably because the climatic conditions are more favorable to the develop- 

 ment of these pests about these smaller lakes than near Lake Erie. The 

 five most troublesome diseases, named about in order of importance are 

 black-rot,' downy mildew,^ or " brown-rot ", powdery mildew,' anthrac- 



' Black-rot (Guignardia bidwellii (Ell.) V. & R.) usually appears first on the leaves where it forms 

 circular, reddish-brown spots on which black pimples, or spore cases, develop. Within these spore 

 cases, at maturity, are the summer spores. These are distributed by the elements to the growing 

 parts of the plant and form new centers of infection. The diseased berries show analogous circular 

 spots bearing spores and as the disease progresses the grapes wither, turn black, and become hard 

 and shrivelled, sometimes clinging to the vine until the following spring. Growing shoots are attacked 

 as well as leaves and fruit. During the winter and spring the resting spores are formed, usually 

 upon the shrivelled berries. 



Treatment consists of destroying as far as possible all diseased fruit, old leaves and prunings 

 and in spraying thoroughly with bordeau.x mixture as follows: — 



1 . Just as the pink tips of the first leaves appear. 



2. From ten days to two weeks after the first spraying. 



3. Just after the blossoming. 



4. From ten to fourteen days after the third spraying. 



5. After an interval of from ten to fourteen days from the fourth spraying. 



2 Downy mildew {Plasmopara vilicola (B. & C.) Berl. & De Toni) is a troublesome fungus attack- 

 ing all of the tender growing parts of the grape. It does most damage to the leaves, upon the upper 

 surface of which it produces greenish-yellow spots of irregular outline. At the same time a loose 

 white downy growth appears on the under side of the leaves. This growth consists of short filaments 

 bearing spores, the summer spores, which are carried by the elements to other growing parts of the 

 plant, thus spreading the disease. Affected berries, if young, first show a brown spot, and become 

 covered with the gray down which distinguishes the fungus. On older berries the fungus causes a 

 brown-purple spot which spreads until it takes in the whole berry, which then becomes soft and often 

 falls, or they may become hard and persist. At this stage the disease is commonly known as " brown 

 rot ". The winter, or resting, spores are produced in the tissue of fruit and leaves and with a 

 thick protective covering. The winter spores are dark, almost black, in color. Downy mildew- 

 spreads and does most damage in hot wet weather. Spra>'ing with bordeaux mixture as indicated 

 for black-rot will keep downy mildew in check. 



•• Powdery mildew ( Uncinttla ticcator (Schw.) Burr.) is caused by a fungus which lives on the 

 surface of the leaves. It subsists by means of sucker-like organs which penetrate the walls of the 

 surface layer of cells. The vegetative portion of the parasite consists of fine white filaments which 

 spread over the surface of the leaves, shoots and fruit. In the summer these filaments send up 

 short, irregular stalks upon which large numbers of barrel-shaped spores are produced in chain-like 

 arrangement. These are the summer spores of the fungus. They are Ixarne in greatest quantity 



