176 



SIXTEENTH BIENNIAL REPORT 



"The formidable list just enumerated — all of whicb constitute a constant 

 daily meuace — shoulcl he a wari-ant for renewed efforts upon tlie part of the 

 Western Plant Quarantine Board to prevent their introduction into our territory, 

 and for an appeal to the legislative and commereial hodies of our several states 

 for Support and Cooperation in this work of protection to our crops and prevention 

 of the burdens of plant quarantines." 



[0 qliüteoiD^ cJrop5 

 00 pioe borK 



tO- 



tbreaä 



rooge-Yellow 

 isfers or? 

 ir?e borK 



Tbreads 

 wbicb iprouT 

 irom Tbe sporcs 

 10 tbe coltimoa 



fy / orQDqe-Yellow 

 ■^y^^^;^ pusTules or> tbe 

 ur>der .sidt of 

 corrant and qooieberry 

 leaves. 



Figure 1. Life cycle of the White Pine Blister Rust. (Loaned by the courtesy of 

 the Bureau of Plant Industry, U. S. Department of Agriculture.) 



WHITE PINE BLISTEK RUST WORK IN OREGON 



George A. Root 



; ' Assistant in Blister Rust Control, Bureau of Plant Industry, 



U. S. Department of Agriculture* 

 The White Pine Blister Rust (Cronartium ribicola) is a destructive disease 

 of the so-called white pines, that is, those piues which bear their needles in 

 ibundles of five each. Due to its severity in Europe, it is impossible to grow white 

 pines there with profit. It was iutroduced into northeastern America from Europe 

 about fifteen years ago, on diseased nursery stock. Since then it has become 

 firmly established in many of the most valuable white pine Stands of New 



»Western branch of the office of Blister Rust Control, in Charge of Mr. G. B. Posey, 

 is located in Berkeley, California. 



