Black Knot is perhaps the most conspicuous disease of cherries. It is common also to plums; in fact, plums suffer more from this disease than do cherries. However, cherries of many varieties are affected with Black Knot, including choke-cherry, wild black or rum-cherry, bird or pin-cherry, and morello varieties. Sweet cherries are said to be much less affected than sours. The English Morello, the standard late sour cherry of North America, probably suffers as much as any of the cherries. At times serious injury is inflicted on this and other varieties, particularly in the eastern United States. In North Carolina, for example, cherry-growing was abandoned in 1906 because of Black Knot injury. The disease also occurs in the West. (For fuller discussion of symptoms, cause and control, see Plum, page 356.)

Frost Injury, Caused By The Action Of Low Temperatures

Cherries are injured more or less every year by frost in localities away from large bodies of water. The sweet varieties are particularly susceptible to Frost Injury, although sour cherries are affected. Gum exudes from the injured bark in early summer, and on cutting into such places large gum - pockets are revealed. (For fuller discussion, see Apple, page 35.)