BUREAU OF PLANT INDUSTRY. 141 



sulphuric acid as a fungicide in controlling the damping-off disease 

 of coniferous seedlings. In certain localities presenting peculiar soil 

 conditions, zinc chlorid and copper sulphate have proved more effec- 

 tive. These fungicidal treatments also kill weeds, and at some 

 nurseries this feature alone pays for the cost of applying treatment. 

 An unexpected result from this fungicidal treatment is the stimula- 

 tion of growth of the conifer seedlings. 



New tree diseases. — Nine newly imported tree diseases have been 

 discovered and studied and with one exception destroyed by cooper- 

 ating authorities so far as found. The exception is. a newly im- 

 ported poplar disease from Europe, Dithichiza populea, which is 

 apparently already so widely distributed by nursery stock as to pre- 

 clude any organized attempt toward eradication. 



White-pine blister rust. — Only a provisional report can be made, 

 as the season's work is incomplete. The blister rust is now epidemic 

 on currants practically throughout Massachusetts, Rhode Island, 

 southern New Hampshire, and northwestern Connecticut. Elsewhere 

 it appears to be well under control, although there are dangerous 

 outbreaks on the Niagara peninsula in Canada and in an area in 

 Wisconsin and Minnesota not far from St. Paul. No trace of the 

 disease has yet been found west of Minnesota. Manv nurseries are 

 situated within the areas of the currant-disease epidemic, and the 

 danger of spreading the disease by nursery stock of either currents 

 or white pines is as great as it ever has been. 



Cedar rust on apples. — Cedar rust on apples continues to at- 

 tract considerable attention and has been severe in certain localities. 

 One of the striking things, however, in orchard pathology has been 

 the fact that in many of the large commercial orchard districts of 

 the eastern Appalachian Mountains where cedar rust threatened the 

 destruction of the value of the orchards, complete or partial eradi- 

 cation of the cedar trees in the vicinity of the apple orchards, usually 

 within a radius of 1 mile, has completely solved the problem in 

 the most practical, simple, and permanent way and at very slight 

 expense. While the destruction of the red cedars is to be regretted, 

 this tree in the vicinity of apple orchards has come to be a veritable 

 pest tree, and where the cedar-rust fungus has been specially abun- 

 dant the necessity for its destruction has been amply demonstraed 

 by the repeated experiences of the past few years. 



Citrus scab. — This disease has become increasingly destructive 

 during the past few years in Florida, especially in grapefruit groves, 

 and investigations were undertaken to extend our knowledge of the 

 life history of the scab fungus in all its details and further to per- 

 fect the methods of control. Spraying experiments carried on indi- 

 cate the possibility of satisfactory control by thorough spray pro- 

 tection of the young fruit. 



Apple bitter-rot. — Practical field tests in perfecting the methods 

 of control of apple bitter-rot have been carried on in the Ozark sec- 

 tion with very satisfactory results. The removal of cankers and dis- 

 eased fruit supplemented by spraying reduced damage by the disease 

 to 2 per cent on early varieties and 1 per cent on late varieties. The 

 orchard in which these field tests were conducted had previously, 



