1917] DISEASES OF PLANTS. 353 



This name is preferred to the name lemon scab, which was originally given the 

 disease when it was considered to attack lemons chiefly. The disease Is known 

 to occur on the sour orange, lemon, citron, certain varieties of grapefruit, etc. 

 Sour scab is said to cause considerable financial loss in the growing of grape- 

 fruit in Florida, Cuba, and the Isle of Pines. 



The disease develops most destructively in seasons and localities which have 

 abundant moisture in the air and soil during the development of the early 

 spring growth. Trees starting later in growth appear less subject to the dis- 

 ease, and it is thought that possibly selection from such individual trees might 

 prove of value in reducing loss from this trouble. 



The cause of the disease is claimed not to have been definitely determined, 

 but among the agents frequently considered to produce the trouble is Cladospor- 

 ium citri. The author's Investigations, it is claimed, indicate that this fungus 

 is only partially responsible for producing the disease. The long-continued pres- 

 ence of water on rapidly growing leaves and shoots and on young grapefruits, 

 together with excessive hydrostatic pressures during growth, is believed to have 

 a causal relation to sour scab. 



From the reports of experiments covering three years, the author believes 

 that spraying with Bordeaux mixture or lime sulphur solution would protect the 

 fruit. Pruning as a method of restricting the spread has proved impracticable 

 and in some cases even injurious. 



Diseases of forest and shade trees, D. C. Babcock (Mo. Bui. Ohio Sta., 1 

 {1916), Nos. 10, pp. 291-296, fig. 1; 11, pp. 333-339, figs. 4).— Popular descrip- 

 tions are given of a number of the more common diseases of forest and shade 

 trees in Ohio, and where definite means are known, suggestions are given for 

 their control. 



An outbreak of white pine blister rust in Ontario, J. E. Howitt and W. A. 

 McCtJBBiN {Phytopathologij, 6 (1916), No. 2, pp. 182-185) .—The Cronartium 

 stage of the white pine blister rust is said to have been found on five culti- 

 vated and four wild species of Ribes in nine counties in the Province of 

 Ontario, and the Peridermium stage has been found on both Imported and 

 native white pines. Black currant plantations have in many instances been 

 severely injured. An examination of imported white pines has indicated that 

 they are the source of infection in the majority of cases. According to the 

 authors' observations, the rust may be passed from currant to currant over 

 an intervening distance of at least 800 yds. Spraying experiments indicate 

 that the rust on currants may be markedly reduced by the application of 

 Bordeaux mixture or soluble sulphur. There is thought to be some evidence 

 that the rust may possibly winter on the currant. 



Methods of preparation and relative value of Bordeavix mixtures, O. But- 

 ler (New Hampshire Sta. Sei. Contrib. 9 (1915), pp. 2-12; Off. Rpt. Bess. 

 Internat. Cong. Vit., 1915, pp. 151-160). — The characters that a copper fungi- 

 cide must possess are noted, and the three types to Mdiich, as previously stated 

 (B. S. R., 31, p. 802), Bordeaux mixtures may be reduced are enumerated, and 

 tabular data reported regarding various phases, properties, and effects of this 

 fungicide. 



The author states that acid and neutral Bordeaux mixtures are less injurious 

 to the grape than are the alkaline preparations, although the toxic value of the 

 unit copper is the same in each of these phases of the fungicide. When imme- 

 diate action is required, the unit copper in acid and in neutral Bordeaux mix- 

 ture is said to be more effective than is that in alkaline preparations, the last 

 named, however, being more adhesive than the other two. 



