Dec. 1896.] INJURIOUS INSECTS AND FUNGI. 291 



The Hop Mildew {Podosphcvra castagnei). 



Fig. 1. 



Perithecia of Podosphcera castagnei. 



Until the weather changed in the late summer and became 

 wet and cold, there was very little mildew, known as mould in 

 the hop districts, upon the hop plants. A few of the typical 

 white spots of mycelium were noticed on the leaves in June, 

 and later, when the " burr " had set, a few of the young cones 

 in some hop grounds were attacked by the fungus, but it did not 

 spread, and little harm was done at that period, which is 

 generally considered to be the most critical time at which mould 

 <£ runs " rapidly if the conditions are favourable for its progress. 

 About the middle of the picking time in the first week of 

 September, after wet, cold weather, it was observed that the 

 cones in many grounds, especially those of Old Golclings, changed 

 colour rapidly, and became red, or " foxy," to use the expressive 

 term of hop -growers, and in some instances the colour and 

 quality of the hops were seriously injured. It was said by some 

 that " red mould " was the cause of this rapid (i going off" of the 

 colour of the cones. Others thought that the alternations of 

 wet with cold, and occasional scorching sunshine, had injured 

 the tender tissues of the cones and turned them red — that it 

 was merely a physical injury. But the "red mould" theory was 

 generally accepted, and examination was made to discover the 

 nature of the fungus causing this serious and widespread injury. 

 It was considered that it could not be due to weather, as the 

 cones on all sides of the poles and those protected by leaves were 

 just as red as those exposed fully to its influences. 



In all cases it was found that the " foxy " cones contained the 

 perithecia, or spore cases, of the fungus Podospheera castagnei, 



