124 EXPERIMENTAL rARMS 



4-5 EDWARD VII., A. 1905 



Another disease of the grape wliicli was doing a great deal of injury at Winona 

 was what we took to be the Grape-leaf Blight, a disease which has not received the at- 

 tention which it deserves. This blight causes tlie leaves to wither a'-id drop, thus pre- 

 venting a free circulation of sap and the proper development and maturing of the 

 fruit. 



The diseases of the grape can be controlled by thorough spraying, but the Avorii 

 muct be done persistently and carefully. 



FUNGOUS DISEASES OF THE GHAPE. 



Anthracnose : Bird's Eye Rot: Scab (Sphaceloma Ampelinum). — This is the only 

 grape disease which has given any trouble at the Central Experimental Farm. It is 

 difficult to control by spraying, but, fortunately, only a few varieties have been affected, 

 Lindley being the worst. This fungus attacl^s leaves, stems, and fruit, but it is on the 

 fruit where it is most noticed. The disease is apparent in depressed patches extending 

 along the stems, which checks the growth. There are also reddish brown patches on the 

 leaves. The stems of the clusters of grapes are frequently affected, and when the 

 disease occurs there the fruit remains green and eventually withers, making an imper- 

 fect bunch. The disease on the fruit occurs in roundish brown depressed spots with 

 a purplish margin, giving somewhat the appearance of a bird's eye. Frequently spots 

 unite and form a large irregular area. This is a verj- difficult disease to control, and 

 thorough spraying with Bordeaux mixture has not checked it to any extent. Spraying 

 before the buds open; 'before blossoming; after fruit has set and ten days later with 

 Eordeanx mixture is recommended. 



Black Rot (Lacsiadia Bidwellii). — Up to quite recent years this dlseas3 was 

 thought to have reached its northern limit, south of lakes Erie and Ontario, but during 

 the last few years in Essex county, and more recently in the Niagara peninsula, it has 

 caused much damage. The appearance of this disease has already been described, but 

 something further must be said regarding it. The spores live over winter on the vines 

 and in the affected grapes, and germinate when growth starts in the spring. The dis- 

 ease attacks the leaves and young shoots, the leaves showing the disease in roundish 

 reddish brown patches, and on the stems it appears in small, long shaped, dark brown, 

 slightly depressed spots, on the surface of which appears the characteristic pustules of 

 the Black Rot. When conditions are favourable, the disease only requires from 8 to 

 12 days from the time the spore germinates until the mycelium has run its course 

 through the fruit and has produced new spores. Before the grape shrinks much in 

 size the mycelium concentrates, as it were, in small masses underneath the skin, and 

 in these are produced the spores. These masses soon break through the skin and the 

 black pustules with the spores appear. The spores are scattered and they reinfect 

 .other fruits and vines. Although it is possible for a new generation of spores to be 

 borne within two weeks, it requires favourable weather conditions for the disease to 

 develop. While early sprayings have in some cases not been found to give the results 

 expected, the life history of the disease shows that it must be wise to endeavour to 

 destroy as many spores as possible at or before the first infection. The first spraying 

 should be made just before blossoming, the second just after the fruit has set, the third 

 and fourth at intervals of about a week — all with ordinary Bordeaux mixture. There 

 should then be three sprsyings with Ammoniacal Copper Carbonate or Soda Bordeaux, 

 T.hich will not discolour the fruit to any extent. Although the disease will probably not 

 be eradicated from a vineyard in one season, the more thoroughly the spraying is done 

 the less trouble there should be. It is now sixteen years since it was conclusively 

 shown that Bordeaux mixture would control this disease. 



Brown Rot: Downy Mildew: Gray Rot (Peronospora viticola). — This is the rot 

 which up to quite recent years proved most injurious in Ontario. The general ap- 

 pearance of this rot as it affects the fruit has already been noticed. Like the Black 



