Hypertrophy, or false blossoms, is erratic in its behavior. Some bogs are free from it, while in others every plant may be diseased. The variety Matthews seems especially susceptible.
The disease is rather limited in its range, being known only in Massachusetts. In 1906 it was unusually severe in that state, destroying a large part of the crop in several bogs. Not only the production of fruit is prevented, but the vitality of the plant is exhausted.
The fruit-bearing and vegetative shoots, runners, are affected. The disease appears usually in the middle of May or soon after the water is removed from the flooded bogs in the spring. The axillary leaf-buds, which ordinarily remain dormant, are affected, in response to the attacks of the pathogene. They produce short shoots with leaves abnormally swollen and distorted. These leaves are pink or light rose-colored. The affected leaves stand close together and bear a slight resemblance to a flower, whence the name false blossoms. This name should be avoided, for there is another disease which passes under this designation. In the genuine false blossom the floral parts are affected; instead of the typical drooping of the flowers, the flower-buds stand erect, remain greenish, and do not set. This is accompanied by a profuse branching of the vines. Until recently the real false blossom was known as "Wisconsin false blossom," but in 1914 it was found in Massachusetts.
Most plants are affected before the blossoms have developed, and thus the production of fruit is prevented. Later in the stage of development the fruiting portions of the causal fungus give to the surface of the distorted parts a fine, grayish, powdered appearance.
The symptoms just described are changes brought about by the fungus Exobasidium Oxycocci. Its mycelium grows within the leaf and stem-tissues, stimulating them to overgrowth. Fruiting stalks, known as basidia, emerge and stand erect on the surface of the affected portion. These are found from May to September, but are most abundant in the earlier part of the growing season. On each basidium four spores are borne. These bring about infections. Further points regarding the life - cycle of the fungus are not well known.
Since .the activities and whereabouts of the pathogene are not clearly understood, it is almost impossible to suggest dependable control measures. No definite remedy is on record.
Shear, C. L. Cranberry diseases. Hypertrophy. U. S. Agr. Dept. Plant Indus. Bur. Bul. 110: 35 - 37. 1907.
Frost is one of the greatest enemies of the cranberry - grower. It is rather erratic in its occurrence, and very difficult for the average grower to predict; hence the damage is done before any precautions are taken.
Danger from frost comes throughout the growing-season. In June, 1903, the yield in Wisconsin was reduced twenty - five per cent, and in early August, sixty per cent.
It is ordinarily supposed that Frost Injury comes about by a settling of cold air from the surrounding higher land on the bogs. This, however, is regarded as of little importance. Frost formation is largely dependent on the temperature of the soil, and on heat-radiation from it as influenced by the conditions of the atmosphere. The influence of drainage, sand, the depth and thickness of the vegetation, especially of moss, seem to be controlling factors in the formation of frost, and its effect on cranberries. It has been noticed that even where the general minimum over a bog was 25° Fahr., if the same were well - drained and sanded, it remained unaffected by frost; while in adjacent plots which were in a moist condition and not sanded, frost destroyed every plant.
It is advised that plants be sprayed with water every two minutes during a frosty night. Or possibly the spraying may be done just about sunrise, thus drawing the frost out of them gradually before the heat of the sun strikes them.
Whitson, A. R., et al. Preliminary report on cranberry investigations.
Formation of frost and protection therefrom. Wisconsin Agr.
Exp. Sta. Rept. 21: 232-233. 1904. Franklin, H. J. Report of cranberry substation for 1912. Frost protection. Massachusetts Agr. Exp. Sta. Rept. 25:210 - 211.