1922,] Hop " Canker " OB " Grow in<;-oii\" ;r>:> 



or two. On scraping away the soil, the lower end of the bine 

 will be found completely severed from the parent plant." 



The cause of the disease was attributed by Professor Percival to 

 the fungus Fusoma parasiticum. During the past ten years the 

 writers have had, from time to time, opportunities for studying 

 the disease, and have been able to confirm the general conclu- 

 sions arrived at by Professor Percival. 



Description of the Disease. — Above ground the presence of 

 the disease is indicated by a wilting of one or more bines at each 

 affected 14 hill"; such bines are usually found to be almost 

 severed at the base and easily come away from the rootstock 

 with a slight pull, a condition which, as noted above, is some- 

 times described by growers as " growing-off " of the bines. This 

 wilting of the bines is accompanied by a canker of the under- 

 ground rootstock, the infected portions being brown and dead. 



The basal parts of diseased bines which have been dead for 

 some time often bear white pustules of a fungus, the conidia 

 produced on these pustules being of the Fusarium type. Bines 

 just beginning to wilt may not show these pustules, but usually 

 the bark and even the wood is brown, and mycelium of a fungus 

 is to be found in the brown tissues. In experiments where 

 particles of such brown tissues were placed on sterilized culture- 

 media, the fungus grew out and eventually gave rise to the 

 Fusarium fructifications, 



If the bines become infected but are not killed until late in the 

 season, their bases become abnormally thickened, presumably 

 owing to the accumulation of foodstuffs travelling downwards 

 from the leaves and unable to reach the rootstock because of the 

 partial severance of the tissues at the junction of bine and root- 

 stock. These swollen bases become invaded by the fungus, 

 which produces its fructifications at the surface. If the fungus 

 is not fruiting at the time the hill is " cut " or " dressed," 

 Fusarium fructifications almost invariably appear within a few 

 days if the basal part of the bine — known as a " stnip rut " 

 when used for propagation — is kept in moist air. 



A serious outbreak of the disease in a " Bramling " hop- 

 garden came under the writers' notice in 1914, and the following 

 notes on observations made there will serve to illustrate a typical 

 case of hop-canker. Many hundreds of bines had been killed 

 during the first three weeks of June of that year. By the end 

 of the month the damage had almost ceased but the check was 

 probably only a temporary one, as in previous infestations in 

 the same hop-garden a certain further number of bines died 



