1^2 EXPERIMENT STATION RECORD. [Vol.35 



a saprophyte, rapidly spreading througli the spot behind the Sphceropsis, and 

 may become a parasite under conditions of excessive moisture. Phyllosticta 

 pirina, P. Hinitata, and Coniotliyrmm pirintim occur as saprophytes but are 

 not able to produce enlargements. The light gray color about some frog-eye 

 spots which have ceased to enlarge is said to be due to P. pirina. Other fungi 

 reported as a cause of this disease are said to occur only as saprophytes. 



A description is given of the relation of the fungus causing Sphaeropsis 

 spots to black rot and canker of the apple. Spraying experiments for the 

 control of frog-eye leaf spot were conducted in various parts of Virginia from 

 1910 to 1914, lime-sulphur solution, Bordeaux mixture, iron Bordeaux mixture, 

 and copper-lime-sulphur being employed. All of these fungicides greatly re- 

 duced the amount of injury, lime-sulphur ordinarily being somewhat more ef- 

 ficient than the others. 



Dimorphism in Coniothyrium pirinum, C. H. Ceabtix {Amer. Jour. BoL, 2 

 (1915), No. 9, pp. U9-JfGl, figs. 15). — Having dealt in a previous paper (E. S. R., 

 29, p. 648) with the morphology, cultural features, and host relationships of 

 C pirinum., the author reports the outcome of pure cultures of this fungus 

 Isolated from apple leaf spots. 



It is stated that C. pirinum is sometimes dimorphic in culture and probably 

 also in nature. Two strains have been isolated, a plus strain fruiting abun- 

 dantly, and a minus strain fruiting poorly which arises in artificial culture by 

 sudden sporting from the plus strain. Minus strains are said to remain con- 

 stant generation after generation. Attempts to develop the strains from each 

 other by continuous selection of extremes were unsuccessful. The cause of the 

 sporting has not been ascertained. 



The gray mold or Botrytis disease of citrus trees, C. C Brtttlebank {Jour. 

 Dept. Agr. Victoria, 13 {191-5), No. 10, pp. 605-60S, figs. 7). —This disease was 

 noted in portions of Australia in 1900, 1911, 1912, and 1913. The rapid progress 

 observed during the latter years has apparently been checked recently by a 

 protracted drought, but it is thought that the disease occurs now wherever 

 citrus trees are grown in tlys region. 



The life history of the fungus and the progress of the disease ai*e described. 

 The fungus can exist either as a saprophyte or as a wound parasite, reproduc- 

 ing by means of conidia or of sclerotia. Infection is favored by wet weather. 



All the smaller infected branches should be cut out and all diseased material 

 scraped from the larger branches and tlie stem, all the removed material being 

 destroyed by fire and all wounds being painted with a mixture of carbolic acid 

 and water in equal parts. A paste prepared by mixing when cool 1 lb. copper 

 sulphate in 1 gal. water and 2 lbs. of quicklime freshly slaked in ^ gal. water, 

 may be applied to diseased places after cleaning them thoroughly. 



The same fungus has recently been found to produce injury or death in case 

 of seedlings of Eucalyptus citriodora and Jacaranda niimoswfolia. 



Citrus canker, F. A. Wolf {V. S. Dept. Agr., Jour. Agr. ResearcJi, 6 {1916), 

 No. 2, pp. 69-100, pis. Jf, figs. 8).— In a paper contributed from the Alabama Ex- 

 periment Station, the author gives an account of an investigation of the life 

 history of the organism Pseudoinonas citri, the cause of the citrus canker. 

 Infection is considered to occur through natural openings and through wounds. 

 The rapid spread of the disease is favored by the simultaneous occurrence of 

 newly exposed cankerous cells and the presence of a film of moisture, especially 

 on young parts of the plant. The bacteria occur for the most part between the 

 cells of the host and cause them to become considerably hypertrophied. 



In addition to the bacteria causing this disease, fungi belonging to the 

 genera Phoma. Fusarium, and Gloeosporium have been isolated from citrus 



