FOREST INSECTS AND FUNGI 131 



these leaves in fifteen to forty days new fruiting bodies are 

 formed, the spores of which may infect either currant or pine. 

 The spores produced on the pine cannot directly infect pine, 

 but must first infect currants. On the pine the fungus remains 

 alive as long as the stem on which it grows; but in the currant 

 it is not thought to be perennial. 



A second kind of spores produced on the currant and goose- 

 berry bushes are able to infect other currants and gooseberries. 

 In this way the disease may travel from currant to currant for 

 many miles in one season. 



Definite knowledge as to how far spores may travel from 

 currant to pine, from pine to currant and from currant to currant 

 is still lacking. The best opinion indicates that distances of 

 one-eighth to one mile render infection difficult and very likely 

 impossible in the case of currant to pine and pine to currant. 

 Spores carrying from currant to currant may presumably go 

 farther. 



The best means of combating the disease are: 



(1) To exterminate currant and gooseberry bushes in the 

 neighborhood of plantations. 



(2) To stop making pure white pine plantations, but instead 

 plant mixtures of white and Norway pines. 



If the white pine is later on killed by the blister rust there will 

 still remain a full stand of Norway pine. 



(3) To inspect annually for several years all white pines 

 located near infected currant bushes and burn all that show 

 infection. 



WHITE-HEART ROT. FALSE-TINDER FUNGUS, POPLAR DISEASE 

 (Fomes igniarius) . l 



The principal diseases of deciduous forest trees are caused by 

 a group of fungi which grow in the heartwood of trees. This 

 species is characteristic of the group. It is impossible to recog- 

 nize the presence of the fungus during the early stages of the 



1 See Bull. 149, U. S. Department of Agriculture Bureau of Plant Industry. 

 "Diseases of Deciduous Forest Trees." 



