86 SALMON: SUPPLEMENTARY 
P. LEUCOTRICHA (Ell. & Everh.) Salm. (Monograph, p. 40) 
F 
Ref. add: Sphaerotheca mali Burr.; Liistner, Mitteil. tuber 4 
Obst und Gartenbau, 16: 82 f/. Igor. r 
Distrib. add: N. America, U. S., New York (57). 
Flosts, add: Pyrus communis. i 
Listner (42) gives an interesting account, accompanied by a 
good figures, of the occurrence of the present species on both the 
leaves and fruit of pear trees in a nursery at Geisenheim, Ger- 
many, where it was the cause of some injury to the trees. Hitherto 
P. leucotricha has been known only on the apple in Europe and 
the United States, and on Pyrus Sieboldi in Japan. i 
P. leucotricha appears to be on the increase in Germany, where 
there have been numerous reports of late of serious injury cause 
by this fungus to apple orchards. Bordeaux mixture has bee i 
found to be ineffectual as a fungicide, but sulphur is stated to g'© : 
good results (see Wehmer 86, 87, and Magnus 44, 45, 46) fo 
Cutting off and burning the affected shoots is, however, a far bet 
ter method of dealing with the disease than spraying, as, unless i 
this method is adopted, the present fungus, like the “ peach mil- 
dew ” (see p. 92), is liable to recur year after year on the same 7 
trees. (See Schlichting 72 *). 4 
The mildew that frequently attacks the young shoots of apple t 
trees in England and in severe cases spreads on to the apples 7 
themselves, covering them with a white powdery film, in all prob- | 
ability belongs to the present species, although up to the present ; 
I have not seen any perithecia from a British locality. | 
Goethe (21) has recorded the occurrence of Sphaerothecd ' 
pannosa on apple trees at Geisenheim in Germany ; according ' i 
specimens (now in the Kew Herbarium), however, sent to m¢ by ; 
Dr. Liistner, the fungus in question is P. /eucotricha. | 
Despeissis (15*) records a fungus as the ‘‘ Apple and i i 
Powdery Mildew (Podosphaera sp.),” from western Australia, 2° 
remarks: ‘This disease, which from its appearance at a later stag 
is also known as ‘Fire Blight,’ is more widespread in some et i 
sons than others. It affects the young shoots of pear and appr 
trees and stunts their growth.” 
