158 DISEASES OF ECONOMIC PLANTS 



densely matted in the central portions of the spot, and 

 less dense towards its circumference. Later these blotches 

 turn brown, irregularly blend into fewer spots, and form 

 large diseased areas. As the spot ages, its threads weave 

 together into a thick felt. 



The young leaves and growing parts are robbed of 

 nourishment, and thus their growth is checked, resulting 

 in serious injury. The l^erries if subjected to one-sided 

 attack become deformed and curved, owing to the retarded 

 growth of the diseased side. They often crack open and 

 decay. Diseased leaves turn brown. Toward the com- 

 pletion of the season's growth small, nearly microscopic, 

 black perithecia are produced in the centers of the diseased 

 spots. 



The damage caused by this disease is excessive and pre- 

 sents the most serious obstacle to the successful culture 

 of the gooseberry. It has quite prohibited the cultivation 

 of the finer sorts of English gooseberries in America and 

 is a grave menace to the culture of gooseberries in Europe. 

 Its destructiveness is due not alone to the injury to the 

 foliage, bush, and to the fruit yield, but also to lack in 

 salability, owing to the unsightliness of the partially dis- 

 eased fruits. 



This powdery mildew has been very successfully com- 

 bated at the New York Experiment Station at Geneva.^ 

 Of a large number of fungicides tried potassium sulphide 

 proved to be most efficient, using one ounce to two gallons 

 of water and spraying seven times. This cost but three 

 tenths of a cent per bush for material, and reduced the 



1 Close, C. P., NY. (Geneva) Agr. Exp. Sta. Bui. 161, November, 1899. 



