:):;2 tiik urvis of no\'a scdiia. -ri;Asi;i;. 



jH'obiiliiy lend III reduce the funiiii^ In- (lc\-uui'iiii:- tlic spores, 

 liut tlicv may aid in their di-^tribulinn hy spicadiiiii' them as 

 they ci'awl alxml. 



Eronotnic Aspects of lite Itiisls. 



The ru-ls arc true parasites and iinahle t(i live except in 

 the tissues of their hosts. They attaeiv many valuable trees 

 and shrubs as well as field and garden crops, and, as they live 

 at the expense of their hosts, often cause serious damage. They 

 cannot he eombatted with much success hy s]>raying with the 

 ]]ordeaux (U- other mixtures. TTsually a knn\vle(lav of their 

 life historv will alone suggest some method of holdiii"- them in 

 check. 



liiisls <if Ihc Conifers: ^Fany rusts of the genus Coleo- 

 spovium and Cronartivni ha\'e their aeeial ^tage^ (»n some 

 species of pine, hut no rusts were found on the pine in Nova 

 Scotia ami none are likely to occur, luiless the I^^uropean 

 currant rust {Gronartium ruhicola) should be introduced. The 

 aeeial stage is found on the white ])ine ( PInus stroh^is) and is 

 said to Iw very destructive in Europe. The uredinial and 

 telial stages on currant bushes does not seem tit br' of much 

 importance. An outbreak occurred at CJeneva, N". Y., in 190G, 

 and in 1001) pine seedlings which were imported from 

 Germany and were distributed through the north eastern 

 United States and Canada were found to lie diseased. The 

 only way to control the fungus would seem to be to destroy 

 the wild species of Ribes in the neighbourhood of the pine 

 forest areas. 



The leaves of the balsam fir (Ahirs halsdniea) are attackcMi 

 by the aeeial stage of the blueberry rust (Oalyptosporn cohunn- 

 aris) by Peridermium halsameum and by a Caeoma. The 

 spores are formed on the under side of the lea^'es whicli turn 

 yellowish. Periderm'nim r.lnCnDtm., the ae<^'ial stago of 

 yfplampsorella elatinn. forms the rather conspicuous witche-s' 

 VuxKjms on the same host. These may be removed in the spring 



