350 Bulletin 73. 



were wrapped with moist cloth and kept moist for several days, 

 while in other cases a moist chamber was made around the twig 

 by covering it with quite a large test tube. Had young buds 

 been inserted in the manner of budding during the month of 

 August in all likelihood the disease would have appeared in a 

 year or two." I know of no successful experiments made in 

 inoculating peach or plum trees from the spores, although such 

 results may have been attained. It is usually considered by most 

 students of this group that it is rather difficult to secure results 

 from the inoculation by spores in mau}^ of the species of Exoascus 

 while in others it is comparatively easy. Sadebeck* succeeded 

 in inoculating Almcs incana with the spores of Exoascus epiphyl- 

 his, and producing the characteristic disease. He says it is easier 

 to produce an infection with this species than with any other of 

 the species of Exoascus known to him. 



Since the mycelium is perennial in the buds or young branches 

 of affected trees no buds should be taken from such trees for bud- 

 ding nursery stock or budding in the orchard. Since nearly all 

 of the affected leaves of the peach trees fall away before the time 

 for the selection of buds, the trees should be carefully selected in 

 the months of May and June in order to avoid those which have 

 the disease. 



Where only a few branches of a tree are affected, pruning a 

 considerable distance below the affected portion might be tried, 

 especially in the case of those plum trees affected with E. mirabi- 

 lis, that is those having the bud deformations. 



It may be well in concluding to give a list of the species of 

 Exoasncs described here as occurring on species of Prunus in the 

 United States, with their host. 



Exoascus deformans (Berk.) Fuckel, deforming the leaves and 

 rarely the shoots of Pnmus persica L,. 



Exoascus pnini Fuckel, deforming the fruit, causing "blad- 

 ders ' ' or plum ' ' pockets ' ' of Prunus doniestica L. 



i:.V(7a^r/«z».y?VzVz>Sadebeck, causing " witches brooms " and de- 

 forming the leaves of Prunus pennsylvanica L. 



Exoascus cerasi (Fuckel) Sadebeck, causing " witches brooms " 

 and deforming the leaves of the same on Prunus avium. 



*Kritische Unters, etc., T891. 



