GRAPE PESTS AND THEIR CONTROL 



219 



ably in all parts of America, do permit their culture for home 

 use in practically all agricultural districts in ^the country. 



Black-rot. 



This is the most widely distributed and the most destructive 

 fungous disease of the grape in the region east of the Rocky 



. FIG. 44. Work of black-rot of the grape. 



Mountains. Fortunately, it is unknown on the Pacific coast. 

 The disease is caused by a parasitic fungus (Guignardia Bid- 

 wellii) which gains entrance to the grape plant by means of 

 minute spores distributed chiefly by wind and rain. Black- 

 rot passes the winter in mummied grapes, on dead tendrils 

 or on small, dead areas on the canes. In the spring, the fungus 

 spreads from these spots to the leaves and forms brown leaf 

 spots about a fourth of an inch in diameter, or oblong, black 

 spots on the shoots, leaves, petioles and tendrils. Later the 

 disease spreads to the fruits, not usually attracting attention 



