266 MANUAL OF TREE DISEASES 



flowering plant hosts are removed, so that none exists within 

 a thousand feet of the pines. A safer distance would be a 

 quarter or a half mile, depending on the contour of the land 

 and the nature of the surrounding vegetation. The elimina- 

 tion of all the plants of the kind required by the blister-rust 

 fungi is not easily accomplished. Nevertheless, it is an efficient 

 and sure method of control, if the eradication is thoroughly 

 done. For a further discussion of the factors involved in carry- 

 ing out eradication methods, see under blister-rust of five- 

 needle pines, page 274. 



Many of the species of Coleosporium that are known in the 

 uredinial and teUal stages on various weed plants have not 

 been connected with the blister-rust stage on pine needles. 

 Either this has not been found and described, or the relation 

 between the stages on the pine and weed host has not been 

 definitely proved to represent the life history of a single species. 

 When all the stages are known, the fungus is called by its 

 Coleosporium name. When only the blister-rust stage is 

 known on the pines, it is classified in the large form genus 

 Peridermium and is given a temporary specific name. 



Below are given brief descriptions of the blister-rusts of the 

 needles of pines, with their distribution, the species of pine 

 affected and the alternate weed hosts, so far as these facts are 

 known. In most cases these blister-rusts cannot be identified 

 except by microscopic examination. 



An inconspicuous blister-rust is known to occur in Maryland 

 on scrub pine. The name of the causal fungus is Coleosporium 

 incons-ptcuum (Long) Hedgcock and Long. The alternate weed- 

 hosts on which its life history is completed are the tickseeds 

 (Coreopsis verticUlaia and C. major). 



Scotch pine needles are affected by Coleosporixim sonchi- 

 arvensis (Persoon) Lev. This disease has been reported only 

 from Wisconsin. The fungus was imported from Europe. 

 The yellow blisters are small, being about one-sixteenth of an 



