1921.] Protection Against Fungi from Abroad. 



657 



woods of Spanish Chestnuts are not usual in Ensiand, but the 

 tree is grown extensively for coppicing for the production of 

 hop and other poles. 



The devastation caused by the Chestnut BHght in the United 

 States is now well known. About 1904 a new b:n>rk disease was 

 lioticed on the Chestnut near New York. A few years later the 

 losses caused by this one disease were estimated at .£10,000,000 

 and have continued since ; yet the parasite is practically harmless 

 in China and Japan whence it came. Dr. W. \. Orton, one of 

 the leading American pathologists, says that " Europe should 

 take warning and exercise every precaution to prevent the intro- 

 duction of this disease." * 



In Pennsylvania some pathologists are now proposing to cut 

 down every Chestnut tree in the state as " for Ihe last fifteen 

 years all efforts to control Blight have failed."! 



The appearance of this disease is very characteristic. At first 

 yellowish brown patches, sKghtly raised, stand out on the sm.ooth 

 healthy bark. Under these patches, if the bark be torn away, 

 can be found the white, spreading fans of myceliam which form 

 a distinctive diagnostic character. In damp weather the tendrils 

 of spores push forth like so many thick buff-coloured or bright 

 j^ellow hairs — they curl and twist and are soft when wet but 

 hard and brittle when dry. We have other diseases in this 

 country caused by fungi of the nearly allied families^ but none 

 so devastating in effect. 



Downy Mildew of Hops. — The least known of the forbidden 

 diseases is the Japanese Downy Mildew, PeronojAasmo'para, 

 humuli. This was seen in Japan in 1905 when it spread rapidly 

 over a hop field near Sapporo. It was found on the picturesque 

 Japanese wild hop a few months later and was evidently native 

 to Japan. 



The leaves show small spots, angular at first, of a darker green 

 than the rest of the leaf, and having a water-soaked appearance. 

 Occasionally small blisters and bumps occur on the adjacent parts 

 of the leaf. Gradually the colour deepens and then, with the 

 death of the tissue, becomes dark brown and on the under surface 

 a thick, downy growth forms which is white, but becomes greyish, 

 resembling somewhat the fluffy growth of Phytophthora on the 

 potato. This disease a few years later was found in the State of 

 Wisconsin in various localities and evidently spreading. 



Should this disease reach England and spre-ad to the hop- 



* Orton, Phytopathology. Vol. IV, No. 1, February, 1914. 



■f Amer. Nut Journ., XII, p. 91, quoted in Botanical Abstracts, May, 1921. 



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