CONTRIBUTIONS FROM THE WISLEY LABORATORY. 373 



XVII.— AMERICAN GOOSEBERRY MILDEW 



(Sphaerotheca mors-uvae (Schwein.) Berk.) 



By F. J. Chittenden, F.L.S. 



This now too well-known disease has been already described and 

 its history detailed in our Journal,* but it will probably be not 

 without interest to recount the behaviour of the gooseberries at 

 Wisley towards it. 



The origin of the outbreak at Wisley is not known. It was first 

 noticed on a few bushes in November 1910, after the leaves had fallen. 

 Careful examination showed that about forty bushes were slightly 

 attacked, some rather worse than others, but none to an extent greater 

 than would follow from an attack starting in late summer, especially in 

 such a wet period as occurred in 1910 (July-October rainfall 8 73 in.). 



None had been seen in previous years, although watch was kept 

 for anything of the kind, and no gooseberry bushes had been brought 

 into the garden for two years prior to the outbreak. A few currants, 

 which are also liable to attack, were introduced, but examination of 

 these showed no trace of mildew. No gardens in the immediate 

 neighbourhood are known to have been attacked, nor are any other 

 gooseberries growing within a mile of the site of the plantation. 

 It would therefore seem that the spores of the fungus were brought 

 into the garden either on some other plant or on packing material, or 

 by wind or insects from a considerable distance. 



The bushes were pruned in January 191 1, every shoot being 

 shortened back over the whole plantation, both on the bushes attacked 

 and on those free from the attack, in the manner known as " tipping," 

 so as to remove all parts of the shoot on which the resting fruits of 

 the fungus might be present. It was, however, feared that the tipping 

 was done too late to prevent many of the perithecia from falling to the 

 ground and remaining as a source of danger in the succeeding season. 

 It was, therefore, a pleasant surprise to find that in the very dry season 

 of 191 1 no trace of the disease was found until the very end of September, 

 and then on one bush onl y, this piece being promptly destroyed. 



The exigencies of cultivation necessitated the removal of the 

 bushes in November 191 1 to a site about 200 yards distant from their 

 former one, and in removing them the greater part of the soil about 

 them was left perforce behind, since it was of so light a nature. It is 

 interesting to note that the common gooseberry sawfly had been a 

 prevalent pest from 1907 to 191 1, but after the removal of the bushes 



* Salmon, E. S. " The Gooseberry Mildew." (Journal R.H.S. xxv. (1900), 

 P- 139) 



Eriksson, J. "Gooseberry Mildew and Gooseberry Cultivation." (Loc. 

 cit. xxxiv. (1908), p. 469), 



