DO DORMANT CURRANT PLANTS CARRY PINE RUST?* 



F. H. HALL. 



It is a peculiarity of certain rust fungi that they 

 Fungi living must live part of the time on host plants of entirely 

 on different different species. The well-known apple rust would 

 plant species, disappear in any locality where all cedar trees were 

 cut down so that none were left on which the 

 so-called " cedar apples " could develop. These " apples " are 

 fruiting bodies of this stage of a fungus, and from them the infection 

 spreads, not to other cedar trees, but to the apple. Here the fungus 

 assumes an entirely different form and bears fruiting bodies of a 

 type very unlike cedar apples. These produce spores which may 

 again infect the cedar. 



Another fungus of this same type appears in one stage only on 

 the pine and in others on the currant. This fungus, with the two 

 diseases it produces, was unknown in the United States until within 

 recent years and is still uncommon, so there is some hope of restricting 

 its spread. This makes it advisable to prevent its transmission in 

 every possible way. On the currant this fungus produces felt 

 rust, a disease of very little economic importance; but on certain 

 pines — those with needles in groups of five, of which the white 

 pine is most abundant and most important — it causes blister rust, 

 a very destructive trouble. 



The fruiting bodies of the fungus in its pine- 

 How the inhabiting form cannot infect other pines, but 

 currant ' very readily pass to species of Ribes (currant and 

 and pine gooseberry), principally the black currant, even 

 fungus though these are at considerable distances from the 

 spreads. diseased pine. On the currant leaves, the fungus 

 produces two fruiting forms, one of which can infect 

 other currant plants and thus spread the disease rapidly among 

 currants, but cannot infect pine; while the other form can infect 

 pine but not currant. 



Reprint of Popular Edition of Lull. 'tin No, .174; for Bulletin see p. 231. 



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