HOP MILDEW 97 



being distributed, as fast as they appear, by rain, wind, 

 insects, etc., greatly facilitate the rapid spread of the 

 disease. As the season advances, the patches become 

 darker in colour, due in part to the presence of the 

 ascigerous form of fruit, the tiny perithecia being first 

 yellow and finally blackish-brown. Each perithecium con- 

 tains a single ascus enclosing eight spores. This stage 

 matures during the winter on the dead parts of the hop or 

 other host-plant; and it is due to the germinating asco- 

 spores in the early summer that the disease first appears. 

 So long as the mildew is confined to the hop leaves, but 

 little injury is done; but if it passes on to the inflorescence, 

 and attacks the young cones, serious damage may result. 



Preventive Means. — Flowers of sulphur sprinkled over 

 the foliage checks the disease. Being a superficial parasite, 

 spraying with potassium sulphide solution or other fungicide 

 would probably be yet more effectual, if commenced suf- 

 ficiently early. Aphides and insects should be kept in 

 check, as these greatly assist in diffusing conidia. Weeds 

 should not be allowed, as the fungus is common on many 

 kinds, and may from thence pass to the hop. 



De Bary, Fungi, Mycetozoa, etc. (Engl, ed.), p. 201. 

 Marshall Ward, Diseases of Plants, p. 149, figs. 



AMERICAN GOOSEBEEEY MILDEW 



(Sphaerotheca mors-uvae. Berk, and Curt.) 



The finer varieties of imported gooseberries have for 

 several years suffered severely in the United States from 

 the effects of a minute fungous parasite which attacks the 

 young leaves and buds, first appearing as a cobweblike 



G 



