350 EXPEEIMENT STATION KECORD. 



killed, none recovering so far as observed. Removal and burning of all such 

 parts in autumn is recommended. 



Other parasitic fungi the occurrence of which is recorded are Entomosporium 

 mespili on English hawthorn from Nova Scotia, Lophodermium nervisequum 

 on Abies sp. from New Brunswick, and Dasyscypha willkommii from Nova 

 Scotia. 



Report of plant pathologist, H. S. Fawcett {Florida Sta. Rpt. 1911, pp. 

 LVIII-LXVIT, figs. 3). — This report summarizes investigations carried on 

 during the fiscal year, the principal studies being made on diseases of citrus 

 trees and in part previously noted (E. S. R., 25, p. 456; 26, p. 449). A number 

 of experiments to control stem-end rot were conducted, but none of the treat- 

 ments gave beneficial results. 



Diplodia natalensis has been found to cause gummosis of peach and ©range 

 trees. In addition to these host plants, inoculation experiments have been 

 made with the cultures of tlie organism on 18 species of native trees. The 

 following 6 species produced gum with the killing of tissue : Wild plum, wild 

 cherry, cherry laurel, prickly ash, sweet gum, and sumac. Four additional 

 species showed bleeding with killing of tissue, but no gum. These were bass- 

 wood, red bud, hackberry, and mulberry. Iron wood and water oak showed 

 slight killing of tissue without any bleeding, while hawthorn, hickory, magnolia, 

 holly, ash. and huckleberry were apparently not affected by inoculation with 

 the fungus. 



Brief notes are given on black rot due to Aliernaria citrt, blue mold rot 

 caused by Penicillium italicum and P. digitatum, scab or verrucosis due to 

 Cladosporinm citri, and on the bi'own fungus of the white fly (Aegerita iceT)- 

 heri). 



Report of plant physiologist, B. F. Floyd (Florida Sta. Rpt. 1911, pp. 

 LXVIII-LXXAI, figs. 5). — The principal work in the laboratory of plant physi- 

 ology has consisted of a study of the nutrition and malnutrition of citrus 

 plants, attention being given to some of the diseases that are supposed to be 

 due to malnutrition. Among these are die-back, melanose, yellow spotting, and 

 frenching. 



Experiments are in progress with organic nitrogenous fertilizers to determine 

 their effect, especially on die-back and melanose, and in conjunction with these 

 experiments studies are being made on the maximum fertilization of citrus 

 trees, particularly the nitrogen fertilization. Heavy fertilizing has been found 

 to cause distui-bances in the nutrition of citrus trees, resulting in the falling of 

 the leaves and fruit, but experiments thus far indicate that the chemical injury 

 shows itself only in the weaker parts of the plants. 



Experiments on die-back have been begun in the citrus experimental grove 

 near Tavares to determine the effect of certain fertilizers on the chemical and 

 physical properties of the soil, upon the trees, and upon the quality and quan- 

 tity of the fruit, and also to study the relation of the fertilizers to insect pests 

 and diseases. The die-back, so far as the plat experiments have gone, seems 

 to be independent of the fertilizers that have been used. 



An extended report is given of the investigations on melanose, a disease of 

 citrus trees which is distributed throughout Florida and is also known to 

 occur in a number of other regions. In Australia the disease is claimed to be 

 due to the fungus Cladosporiutn hrunneo-atrum (E. S. R., 12, p. 655), but 

 American investigators have never been able to isolate any fungus in cultures 

 made from diseased material. Melanose seems to affect all varieties of citrus 

 trees in Florida, the greatest injury being done to the fruit. The gross and 

 microscopic characters of the disease are described, and the author concludes 

 that it is probable that melanose is not caused by unfavorable growth factors, 



