1919] DISEASES OF PLANTS. 53 



The apple tree anthracnose and how to control it, L. Chtlds {Better Fruit, 

 13 U918), No. 5, pp. 7-9, figs. 3). — This canker disease of the apple is said to be 

 confined chiefly to sections west of the Cascade Mountains, and its development 

 reaches its height in sections of abundant rainfall. Burgundy mixture, prop- 

 erly made up to 3 : 3 : 100, has given the best results as regards control. 



Brown rot of apples, H. Wormald (Jour. Bd. Agr. [London'], 25 (1918), No. 3, 

 pp. 299-302, pis. 2). — The progress of the causal fungus, Monilia (Selerotinia) 

 fructigena, after its inoculation into sound apples is here described. Dis- 

 cussion is given also of spur canlver. 



Infection and immunity in apple rust, N. J. Giddings (West Virginia Sta. 

 Bui. no (1918), pp. 71, figs. 50). — The author reviews the results of investiga- 

 tions undertaken for the purpose of securing definite and reliable information 

 regarding the apple rust due to Gymnosporangium juniperi virginiance, and the 

 factors which result in the infection of the apple or cedar in some instances 

 while in others there is apparent immunity. A previous account of some of 

 the investigations included in this bulletin has already been noted (E. S. R., 

 35, p. 49). 



Leaves of the variety York Imperial have been found usually susceptible to 

 rust from 15 to 25 days after they unroll from the bud, the length of the period 

 being closely associated with growth conditions. Infection data based on 

 periods of rainfall, discharge of sporidia, etc., are considered to offer little 

 definite proof that infection has taken place, since abundant sporidia discharge 

 has been observed without any infection. Sporidia are not discharged in 

 appreciable numbers at a temperature below 50" F. Under optimum condi- 

 tions a fairly abundant discharge of sporidia may be observed in less than 

 three hours after first moistening a mature sorus, slight evaporation apparently 

 favoring the discharge. 



The greatest injury to apple trees is said to be due to foliage infection. A 

 severe rust infection may result in deformed fruit, general reduction in size of 

 fruit, and great loss of vigor in the tree, and the results of severe infection 

 may apparently persist for more than one season. A large percentage of fruit 

 may show -ust if the infection occurs about the time the blossoms fall. 



The author has observed marked variation in susceptibility of red cedar 

 trees to this disease. 



On the apple, rust may be controlled by the use of sprays, but this method is 

 not considered practical in commercial orchards. The destruction of cedar 

 trees for a radius of two miles about susceptible orchards is recommended, and 

 the cost of removing the cedar trees has not been found excessive under West 

 Virginia conditions. 



Winter injury to cherry blossom buds, R. H. Roberts (Proc. Amer. Soc. 

 Hort. ScL, 14 (1917), pp. 105-110, figs. 2). — A study was made in the spring of 

 1917 of severe winter injury to cherry trees of several varieties occurring in 

 Door County, Wis., near Sturgeon Bay ; also of injury in the Bayfield district. 



A large number of blossom buds was present. There was no die-back. Fre- 

 quently only 1 or 2 of the 4 or 5 blossoms within a bud were killed. In 1917 

 the injury, while less severe than the previous year, followed the same relative 

 lines as regards varieties. Exposure did not appear to liave any influence as 

 regards degree of injury. Trees partially defoliated by shot-hole fungus the 

 previous year and young trees suffered less than other trees of the same vari- 

 ety, being also later in blossoming. In old Richmond trees, spurs of medium 

 length suffered most injury ; also along the terminal growth the injury to the 

 lateral buds was more noticeable through the central part of the growth than 

 at the base and the tip. The larger buds showed more injury. The last lateral 



