50 



S 50 - 



(T 50 



50 



-[ 1 1 1 1 1 1 r- 



lopoo' 



8,100' 



H 1- 



1— 



8,100' 



15 30 

 JUNE 



Figure 16.— Phenology of C. comandrae and 

 lodgepole pine at four elevations of simi- 

 lar aspect in Wasatch National Forest in 

 1965. The bars represent presence of 

 spores of various stages: aecial, pycnial, 

 uredinial, and tehal. Relative frequency 

 and duration of sporulation are indicated 

 by vertical and horizontal extent of the 

 bar, as in figure 15. Growth of pine in 

 terms of branch shoot length is shown 

 by the curves; comandra was absent at 

 the two higher elevations. 



aspect in adjacent Idaho. Temperature and relative 

 humidity were recorded by hygrothermographs in 

 shelters (Hungerford 1957) that were placed so that 

 the sensors were about 4 to 6 feet high near cankers 

 of lodgepole pines and about 0.5 foot to 1 foot high 

 near comandra plants. Precipitation was measured by 

 recording rain gages located in open areas near 

 comandra. Fifteen branch leaders and 30 current-year 

 needles of lodgepole pine, and 15 shoots of comandra 

 were marked and measured weekly. Pollen casting by 

 pine and flowering of comandra were noted. Presence 

 of aecia and pycnial oozing were recorded for 15 

 cankers in each plot. Development of uredinia and 

 telia on the 1 5 marked comandra shoots in each plot 

 was also noted. Periods of spore dissemination were 

 determined by spore traps (fig. 17) placed near sporu- 

 lating structures of infected plants. Seasonal traps 



consisted of petrolatum- or glycerine-jelly-coated 

 glass microscope slides on a continuously moving 

 belt; an opening above the slides allowed each point 

 on the shdes an exposure of 6 hours to deposition of 

 spores by gravity. Trapping was also done intermit- 

 tently by a suction trap somewhat similar in oper- 

 ation to the Hirst trap (Hirst 1952). Microscopic 

 examination of slides showed the presence of spores, 

 and their position along the slides showed when 

 spores were trapped. 



A summary of spore-trapping data, host 

 phenology, and weather is presented in figures 18, 19, 

 and 20. Although aecia were present on some cankers 

 from early June to late September, the vast majority 

 of aeciospores were dispersed in June and July. 

 During June, general rain associated with frontal 

 storms is fairly common in this area. Comandra has 

 already made most of its shoot growth by the time 

 aeciospore inoculum arrives. Perhaps this rust-free 

 period accounts for the ability of comandra to remain 



Figure 17. -Spore-trapping device. A clock drive 

 pulls a series of glass slides on a belt 

 beneath an opening. This trap is 

 equipped with a battery-operated ex- 

 haust fan so that air is drawn through a 

 glass tube and particles come in contact 

 with glycerine-jelly-coated glass slides. If 

 the intake tube is replaced by a hori- 

 zontal slit and the exhaust fan is not 

 used, this device can trap particles that 

 settle by gravity onto sticky slides. 



18 



