1922.] Hop " Canker " or " Growing-off." 357 



fire being at the side of the garden. However, a few straps 

 from diseased hills had been left lying on the ground for about 

 two days and on some of these there were pustules which proved 

 to be the fructifications of the Fusarium, although none of the 

 hills, as they were uncovered and examined that day, showed any 

 pustules. It is evident therefore that if diseased portions of the 

 plants are not destroyed immediately, but are left lying about 

 ;n the hop-garden, they serve for the continued development and 

 • dissemination of the fungus. It seems probable that the fungus 

 can remain alive even when the " strap cut " in which it is 

 living becomes desiccated. Infected " strap cuts " from the 

 hop-garden referred to above were brought into the laboratory 

 in June and allowed to become air-dried at room temperature. 

 In the following February they were moistened and placed on 

 damp filter paper in a covered dish. Within four days mycelium 

 had grown out and already conidia, in general resembling those 

 seen on the froshly-killed straps but not produced in definite pus- 

 tules, had developed. The rapid development of mycelium and 

 fructifications suggests that the growth had arisen from internal 

 mycelium rather than from chance conidia on the surface, but 

 the experiment must be repeated under more controlled con- 

 ditions for confirmation of this point. 



In another case, the farmer has described the damage inflicted 

 as follows : — " In some years, in my Rodmersham Golding hop- 

 garden, I lose a small percentage of bines, which die off both in 

 burr and in full hop. One season we had a most disastrous time 

 — they were a wonderful looking crop, till they started dying both 

 in burr and hop and continued to do so up to and through 

 picking. I should say we lost about 30 per cent, of the crop." 



In some cases " canker " may appear soon after the planting 

 of the hops. A Worcestershire grower wrote in 1914 : — " t am 

 sending you the enclosed hop roots. They were planted last 

 year as yearling roots. You will notice that the body of the plant 

 is going rotten. There are thousands of plants like them in the 

 hopyard." The specimens sent bore the same fungus as found 

 in other cases of hop-canker. 



As will be inferred from the above accounts, hop " canker " 

 is a sufficiently serious disease to cause appreciable damage. 

 As a rule only a certain number of the " bines " on any one 

 hill die off, and the whole plant— the " hill "—is not generally 

 killed. Cases have occurred, however, where from 5 to 10 per 

 cent, of the hills in a garden have been completely killed. Where 

 the hops planted belong. to a variety which is particularly suscep- 



