382 F. M. Rolfs 



and branches of Wickson and Whitaker varieties of plum. Jackson 

 (1907) reports a similar disease from Delaware, and states that consider- 

 able injury results to the plum orchards in that State. Smith (1905 b, 

 figs. 11, 12, 15, 70, 72, pi. 19) gives diagrams of sections through 

 diseased plum leaves and fruit tissue, and illustrations of diseased plum 

 fruit. Rorer (1909) records a detailed study of the disease on leaves, 

 twigs, and fruits of peach. Smith (1911) discusses the disease on plum 

 leaves and fruits, and gives illustrations of diseased plum fruits as well 

 as sections through diseased fruit tissue. Heald and Wolf (1912) report 

 the occurrence of a bacterial canker on plum at San Antonio, Texas. 

 Lewis (1912) describes a bacterial canker on plum twigs and records the 

 results of several inoculation experiments. He gives illustrations of can- 

 kers on twigs four and six years of age. 



The disease was first brought to the attention of the writer in 1904, 

 when he was Botanist and Horticulturist at the University of Florida. 

 Many letters were received from fruit growers in northern Florida and 

 southern Georgia, complaining of a shot-hole condition of peach and plum 

 leaves accompanied by considerable premature defoliation. The foliage 

 of the different varieties of peach and plum trees in the university horti- 

 cultural orchard also developed the shot-hole condition, and in most 

 cases fell prematurely. Other duties prevented the writer from under- 

 taking extensive investigation of the problem at that time. However, 

 on taking up work at the Missouri State Fruit Experiment Station in 

 1906, he found that the blackened areas, so common on the peach twigs 

 in northern Florida in 1905, were even more abundant on the peach and 

 plum twigs in Missouri. Additional observations have brought out the 

 fact that the disease is more or less injurious also to the apricot and the 

 nectarine. 



GEOGRAPHICAL DISTRIBUTION 



It is not easy to obtain information as to the distribution of this disease, 

 since a bibliography of the literature relating to shot-hole injury of stone 

 fruits shows that the injury is usually attributed to the work of fungi. 

 This is not surprising, as lesions resulting from various causes resem- 

 ble one another so closely that it is often impossible to determine 

 exactly the causal factor without the aid of a microscope, and it is not 

 always possible even with a microscope. The disease has been reported 

 by investigators as occurring in Arkansas, Connecticut, Delaware, Georgia, 



