ABSTRACT OF PAPER BY HUMPHREY

Filbert. Black knot, Cryptosporella anomala

Humphrey, James Ellis. Mass. Agr. Exp. Sta., 10th an. rept., 1892, p. 242-243.

The author describes this fungus as killing the canes of the European hazel, Corylus avellana, at Palmer, Mass. The fungus appears in the form of protuberances with elliptical bases that burst the bark and rise rather thickly from the affected portions of the branch. The diseased portion is sunk below the surface of the healthy part. The interior of the protuberance, which is the fruiting part of the fungus, contains numerous black, flask-like structures whose tips reached the surface. Within the cavities of these flasks are formed the very numerous spindle-shaped spore cells, each containing, when ripe, eight colorless elliptical spores. The author noticed that the inner bark on the part of the branch occupied by the fungus is reduced to a narrow black line between the wood and the outer bark. This reduction in the thickness of the inner bark explains why the surface of the affected parts is sunken. If the entire circumference of a cane becomes involved, the result is that it is girdled, and the part beyond necessarily dies. The attacks of this fungus on the host-plant are essentially similar in their results to those of the black knot of the plum, though the immediate effect on the inner bark is here one of atrophy, while in the latter case it is one of hypertrophy. The fungus is also related to the black-knot fungus on the plum, but its life-history is not yet known. There may be other spore forms in its life cycle, and therefore it is impossible to give any more definite suggestions for avoiding it than to recommend that infected branches be cut away well below the point of infection and burned as soon as they are seen to be infected.