DISEASES OF PLANTS. 241 



Bordeaux mixture should be sprayed ou the plants immediately after the 

 blossoms have fallen, but such treatment is ineffective after the disease has 

 become evident. 



The oak fungus disease of fruit trees, W. T. Hobne {Mo. Bui. Com. Hort. 

 Cal., 3 (1914), No. 7, pp. 215-282, figs, a).— The author gives an account of 

 experiments with Armillaria mcUea as a very common and serious disease of 

 orchard trees in California. The fungus appears to live for a long time in 

 soil containing roots of various wild or cultivated plants, sometimes destroying 

 whole orchards by spreading, though slowly, from root to root and tree to tree 

 by means of its rhizomorphs. 



Cultivation of nonsusceptible plants, as alfalfa, for several years is recom- 

 mended. Treatment of individual trees is said to be usually disappointing. 

 Treatment of affected spots includes encircling ditches, also soil sterilization, 

 for which purpose carbon bisulphid is said to offer the most promising agency 

 so far, though care is essential to avoid overdosing. Caution is advised as 

 regards planting infected areas with supposedly resistant trees. Fine roots 

 are thought to be less liable to infection than larger ones. 



Peach cankers and their treatment, R. A. Jehle (New York Cornell 8ta. 

 Cir. 26 {1914), pp. 53-6ff, figs. 8). — Two types of cankers, brown rot cankers and 

 cankers caused by winter injuries, are said to be very common on peach trees. 

 Several other types are sometimes found, but are said to be not abundant. 

 The author describes the brown rot cankers due to Sclerotinia fructigena and 

 frost cankers, giving suggestions for their control. 



The treatment involves the cutting out of the infected portions of trees and 

 coating the cut surface with gas tar as soon as the wound has dried. The gas 

 tar is said to act as a disinfectant and preservative, and no other treatment is 

 necessjiry. 



Peach leaf curl fungus, G. Quinn {Jour. Dept. Agr. 8o. Aust., 18 {1914), 

 No. 1, pp. 32-37). — Results are given of tests carried out with Exoascus de- 

 formans, the cause of peach leaf curl, during 1913, also in comparison with 

 figures previously reported (E, S. R., 30, p. 50). It is stated that Burgundy 

 mixture proved superior to all others except the standard Bordeaux mixture, 

 also that the action of lime sulphur shows promise in this connection. 



Violent outbreak of currant rust, E. Noffbay {Jour. Agr. Prat., n. ser., 27 

 (1914), No. 23, pp. 722, 723).— The attack on several species of Ribes is de- 

 scribed. The removal and destruction of diseased portions and plentiful em- 

 ployment of fungicides are prescribed. 



Citrus canker, C. W. Edgerton {Louisiana Stas. Bui. 150 {1914), PP- 3-10, 

 figs. 2). — A report is given of citrus canker, a recently recognized disease that 

 the author says is particularly serious on grapefruit and Citrus trifoliata, but 

 also attacks sweet oranges and Satsumas and sometimes occurs on kumquats. 



All above-ground parts of the plant are subject to the attack, the appearance 

 of the spots varying according to the part of the host upon which they are 

 present. The author states that the disease is known to occur in practically 

 all the Gulf States. Its origin has not been definitely settled, although it is 

 believed that it probably came from Japan on nursery stock, or from Brazil, 

 where a similar disease due to DidymeUa citri was described some time ago by 

 Noack (E. S. R., 13, p. 258). 



No definite means of control are known, but the author suggests the destruc- 

 tion of diseased material, spraying with a good fungicide, and rigid inspection 

 of citrus stock, followed by a strict quarantine on all infected nurseries. 



Pecan rosette, W. A. Orton and F. V. Rand {U. S. Dcpt. Agr., Jour. Agr. 

 Research, 3 {1914), No. 2, pp. 149-174, pis. 5, fig. /).— Pecan rosette, which has 

 been the subject of investigation for several years, is said to be generally 



