DISEASES OF CULTIVATED PLANTS 499 



it a fine gray, powdery, or mealy appearance. Finally the affected 

 part of the leaf becomes light brown, and if the disease 'be severe the 

 leaves fall. The fungus produces a similar appearance upon the 

 young shoots. Berries which are attacked take on a gray, scurfy ap- 

 pearance, become specked with brown, and fail to develop further. 

 Affected grapes when nearly half grown sometimes burst open on 

 one side, exposing the seeds. The fruit does not become softened and 

 shrunken as when attacked by the downy mildew. The powdery 

 mildew is usually more prevalent during dry, hot seasons than in 

 wet ones. It differs in this respect from most of the other grape dis- 

 eases. In California this is the principal fungous disease of the 

 grape. 



Bordeaux mixture, as recommended for the black-rot, will pre- 

 vent this disease. Where this trouble alone is to be combated it may 

 be successfully done by dusting with flowers of sulphur. East of 

 the Rocky Mountains, however, it should be treated with Bordeaux 

 mixture, as it is rarely likely to occur alone. (F. B. 284.) 



Anthracnose. Anthracnose (Sphaceloma ampelinum) has also 

 been called bird's eye rot, on account of the peculiar spots it pro- 

 duces upon affected grapes. Like most of the other diseases of the 

 grape, it attacks the leaves and shoots as well as the fruit. On the 

 leaves it at first appears as minute, irregular, dark brown, slightly 

 sunken spots, having a darker margin. These spots usually become 

 lighter colored when old, and frequently crack or fall out, leaving 

 irregular holes in the leaves. This disease presents much the same 

 appearance on the shoots as on the leaves, though the spots are fre- 

 quently larger and more sunken. They also tend to run together 

 and form irregular patches. 



The disease is most characteristic and conspicuous upon the 

 fruit. The spots are usually brown at first and surrounded by a 

 narrow, dark purplish margin; they increase in size and gradually 

 become grayish white and somewhat sunken. Frequently two or 

 more spots unite and cover a considerable part of the berry. The 

 affected tissues do not become softened, as in the case of the downy 

 mildew, but the fruit becomes hard and more or less wrinkled. If 

 only a small part of the berry is affected it may continue to grow, 

 causing the diseased area to rupture and the seeds to become ex- 

 posed. The bursting of the berries and the exposure of the seeds 

 may, however, be produced by other causes, such as the powdery 

 mildew and certain physiological disturbances. 



On the diseased areas the minute spores or germs of the fungus 

 are frequently produced in immense numbers. The fine, thread-like 

 filaments which constitute the vegetative part of the parasite live 

 during the winter in the tissues of the vines and are ready for active 

 growth in the spring. 



The anthracnose is quite widely distributed in this country, but 

 fortunately has not caused any great general loss. It should be 

 carefully watched, however, as, when once well established under 

 favorable conditions, its eradication is very difficult. Certain va- 



