begin casting basidiospores. The rate of casting is 

 rapid for about 24 more hours if conditions remain 

 favorable. Teliospores germinate over a range of 

 temperatures of 6° to 24° C, but do best at temper- 

 atures from 13° to 23° C. 



Basidiospores are easily injured by desic- 

 cation. Because they are delicate, effective dissem- 

 ination of basidiospores is probably limited to only a 

 few miles. Best germination occurs at about 13° to 

 23° C. Basidiospores derived from fresh telia germi- 

 nate by means of germ tubes, but those from old teUa 

 more frequently form secondary basidiospores. Thus, 

 fresh young telia are probably more effective 

 inoculum for pines. Infection of pines occurs in 

 needle-bearing shoots, but the means and exact site of 

 infection are still unknown. Maximum infection in 

 greenhouse trials occurred in seedlings held 48 hours 

 in mist chambers at 20° C. 



Outbreaks of comandra blister rust in lodge- 

 pole pine occur only rarely in the Rocky Mountain 

 States because the complex series of climatic and bio- 

 logical events necessary for large-scale infection are 

 seldom satisfied. An abundance of aecial inoculum 



during rainy June weather results in abundant infec- 

 tion of comandra in most years. Thundershowers in 

 July and August tend to intensify infection by means 

 of uredinia, so that comandra plants near lodgepole 

 pine stands infected with comandra rust generally 

 become heavily infected with this rust. However, 

 despite the presence of large masses of telial 

 inoculum, infection of pine usually does not occur 

 because summer and early autumn weather does not 

 permit it. Thundershowers sometimes provide condi- 

 tions satisfactory for production and perhaps short- 

 range dissemination of basidiospores, but conditions 

 seldom remain favorable long enough for infection of 

 pines. Extensive outbreaks of pine infection probably 

 occur only when large warm frontal rains invade and 

 remain in the region for several days during summers 

 when there is an abundance of highly viable telial 

 inoculum. Fortunately, this seldom happens in the 

 Rocky Mountain States. By autumn, viable telial 

 inoculum is less plentiful and though frontal storms 

 are more frequent, prevailing temperatures are usually 

 too cool for successful pine infection. While these 

 studies point out the reasons for infrequent outbreaks 

 of comandra rust in lodgepole pine, experience 

 reminds us that when mass infection does occur, 

 damage continues for many years over large areas. 



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