Cranberries and closely allied plants are affected by the gall disease. Among these plants may be noted: azalea, sheep-laurel, calfkill, leather leaf, huckleberry, winter - green and sweet pepper bush. These are particularly affected when growing along the edge of an infested bog.
The disease was discovered about 1886 in New Jersey. For some time it was thought that the trouble was confined to a single meadow in that state, but now it is known to occur as far north as Newfoundland. Badly infested meadows are rendered practically worthless. In 1889 the American Cranberry Growers' Association at its meeting passed resolutions out of which came a state law for the prevention of the spread of fungous diseases of plants. This law included cranberry gall. Since that time the disease seems to have been less destructive, although it is doubtful whether this fact has any connection with the legislation just mentioned.
The first signs of gall appear about May first, and by July first the disease is well advanced. As the name indicates, galls are produced. They vary in shape, depending on the part affected, although in general they are cup-shaped. They measure from one-twenty-fifth to one-thirty-sixth of an inch in thickness and length. The galls are found on young stems and leaves and even on the flowers and fruit. Their color is reddish, so that the disease has been called red rust. A badly infected plant presents in its entirety an unusually red color.
The gall disease is caused by a fungus, Synchytrium Vaccinii. The pathogene is of a low order and possesses no mycelium. Within each gall globose bodies, sporangia, are produced. And within each sporangium a mass of swarm - spores develop in the spring. The sporangia rupture and the spores are liberated. The spores are motile and move about in water very easily; in fact, they are dependent on abundant moisture for their dissemination. Possibly the fungus is carried from one place to another through the air on the feet of birds, or by the wind. It should be borne in mind that while the cranberry is an evergreen, the other hosts, like azalea and huckleberry, are deciduous, dropping their foliage which might drift for long distances over the snow crusts in the winter. April floods spread the fungus rapidly. Should it enter a bog at the head of a stream, the fungus would quickly spread to all plants growing along that stream below the point of entrance.
It is advised that bogs be burned over in the early winter. In such an operation the other hosts already listed should be taken into account. It has been suggested that withholding the water and keeping the bogs dry in the winter and spring might keep the fungus in check.
Halsted, B. D. Cranberry gall fungus. New Jersey Agr. Exp. Sta.
Rept. 10: 233 - 234. 1890. Halsted, B. D. The gall fungus. New Jersey Agr. Exp. Sta. Rept.
11: 332-334. 1891. Halsted, B. D. Some fungous diseases of the cranberry. I. The cranberry gall fungus. New Jersey Agr. Exp. Sta. Bul. 64: 4 - 16.
1889. Shear, C. L. Cranberry diseases. Synchytrium Vaccinii Thomas.
U. S. Agr. Dept. Plant Indus. Bur. Bul. 110: 37 - 38. 1907. Goff, E. S. Insects and diseases injurious to cranberries. The cranberry gall fungus. Wisconsin Agr. Exp. Sta. Bul. 35: 16.