1919] DISEASES OF PLANTS. 645 



reduced the infection somewliat. Disinfection with formalin and with hydro- 

 gen peroxid was not completely effective. Treating slightly moistened infected 

 seed wdth a mixture of finely powdered copper sulphate crystals and dry sodium 

 carbonate suppressed the disease entirely. 



Curtailing potato diseases, W. A. Okton (Potato Mag., 1 (1918), No. 2, p. 

 12). — This paper contains a brief account, with discussion, of mosaic and other 

 diseases of potato in the Northern States as related to crop failures in other 

 sections obtaining seed potatoes from such localities, the system of seed cer- 

 tification now in course of development in Northern States, the production of 

 disease-free seed potatoes, and the control of potato diseases by spraying. 



Cooperative spraying [of potatoes for late blight] in Vermont, B. F. Lut- 

 MAN (Potato Mag., 1 (1918), No. 2, pp. 10, 26). — This is an account of the or- 

 ganization and operation of an arrangement for community spraying of pota- 

 toes, primarily for late blight, in parts of Vermont. A 50-acre unit was 

 employed, and Bordeaux mixture (early at 3:3:50 and later at 4:4:50) was 

 used, from one to four applications being made. A 50 per cent gain in produc- 

 tiveness is claimed. The claim is made also that potato rot was decreased by 

 spraying. 



Is crown gall injurious to apple nursery stock? S. B. Frackee (Jour. Econ. 

 Ent., 11 (1918), No. 1, pp. 133-135). — The author reports the results of observa- 

 tions by himself regarding the effects of crown gall on apple trees in Wisconsin 

 as related to the size of nursery stock and to fruit production. 



In three out of four nurseries discussed, it was found that without respect to 

 variety, the infected trees, if their sale were permitted, would yield (on ac- 

 count of their indicated classification) 17 or 18 per cent less gross returns 

 than would a similar number of noninfected trees, since the infected nurseries 

 show a much larger number of seconds. Although in many cases there seems 

 to be a tendency for the infection to decrease the vigor of the plant without 

 forcing its size below the commercial value, there is a great diminution in the 

 number of first-grade trees when infected and an increased number of seconds, 

 not a single nursery or variety showing as great a proportion of trees of salable 

 size among those having crown gall as in those free from that disease. This 

 reduction in size of apple trees in Wisconsin nurseries is thought to be the 

 direct result of crown gall infection. 



Avocado scab, H. E. Stevens (Florida Sta. Press Bui. 289 (1918), pp. 2). — 

 An account is given of a new and apparently undescribed disease wliich has 

 come to the author's attention within the last two years. The disease is char- 

 acterized by the formation of definite spots or blemishes on young leaves and 

 tender shoots, severe attacks causing the leaves to curl or become distorted. 

 The more mature leaves do not seem to be affected. The fungus, Cladosporium 

 citri, is thought to be a strain of the same that causes citrus scab. Spraying 

 with Bordeaux mixture and avoidance of shade and crowded condition of the 

 trees are suggested as means of control. 



Eeport of plant pathologist, H. E. Stevens (Florida Sfa. Rpt. 1918, pp. 62- 

 67, figs. Jf). — The principal disease reported is that of the avocado scab noted 

 above, which received additional investigation. It has been found that strains 

 of the fungus isolated from avocado and from citrus seem to be identical so far 

 as habits of growth and cultural characters are concerned. 



A description is also given of a second disease, avocado fruit spotting, which 

 seems to be of fungus origin, although this has not been definitely determined. 

 In some few ca.ses the disease has been observed on the variety Trapp, though 

 the spotting seems to be confined mainly to seedling fruits. About the time the 

 fruit is approaching maturity the disease makes its appearance, the spots being 

 quite evident on the ripened fruit. Spotting in matured fruits often results 



