PODOSPHAERA "i^ 



old trees but is especially common on " suckers," coming up 

 around large trees in the orchard and nursery." Ammonlacal 

 carbonate of copper and Bordeaux mixture were found efficacious 

 as fungicides. It is probable that the common American " apple 

 powdery mildew " disease, generally attributed to P. oxyacanthac, 

 is in many cases caused by the present species. 



Sorauer has given an account in Hedwigia (332) of a mildew 

 disease of apple trees, in which the fungus is identified as 

 " Sphacrotheca Castagnci Lev. f. malir Professor Sorauer kindly 

 sent me a series of microscopical slides of this mildew, and in these 

 the characteristic perithccia of the present species are clearly to 

 be seen. The thick-walled septate rigid appendages are wrongly 

 described in Hedwigia as being basal. They are in reality (as the 

 specimens show) apical ; most of the perithecia possess also the 

 characteristic root-like basal appendage. Professor Sorauer [loc. 

 cit.) gives some interesting details of the manner in which the 

 fungus attacks the apple trees, and mentions that, in severe cases, 

 the weaker shoots of the tree are killed. It is also stated that a 

 hibernation of the mycelium takes place on the young shoots. 



Cobb (73, p. 279) gives an account of a disease pre\'alent in 

 Australia, called the "powdery mildew of the apple." No peri- 

 thecia were found by the author, although the fungus is referred 

 to " P. Kiinzei Lev." It is, however, more probable from the de- 

 scription that P. Icucotricha is the cause of the disease. Some m- 

 teresting information is given, as follows : " No account of the 

 diseases of the apple would be complete without mention of the 

 powdery mildew which does so much damage to young apple- 

 trees (especially seedlings) in nurseries. In Australia the disease 

 is by no means confined to nurseries. I have repeatedly had ex- 

 amples sent in from trees two, three, and four years old ; in fact, 

 orchardists send in this disease oftener than any other apple disease, 

 scab excepted ; so there can be no doubt that it is a plague to 

 them as well as to nurserymen. * * * The leaves near the ends of 

 the branches are the first to go." Spraying with ammomo-car- 

 bonate of copper or Eau Celeste is recommended. 



Although P. Icucotricha is at present supposed to be a rare 

 species, it will very probably prove to be widely distributed and 

 common, and has most likely been hitherto passed over by my- 



