Table 1 . - - Amount of limb rust infection in Bryce Canyon National Park in 1935 and 1965 

 by percentages of live pines 6 inches d.b.h, or larger in a belt transect^ 



Infection class 



1935 



1965 



(Basis: 1401 trees) 



North 

 (basis: 462 trees) 



South 

 (basis: 459 trees) 



Average 

 (North-South) 



Early 



Intermediate 

 Advanced 

 Near -lethal 



Total 



5.0 

 4.9 

 4,7 

 3.2 



17.8 



Percent 



1.7 

 4.3 

 6.5 

 0.7 



0.7 

 1.7 

 4.1 

 0.7 



1.2 

 3.0 

 5.3 

 0.7 



13.2 



7.2 



10.2 



Length of the base transect surveyed in 1935 was 12.6 miles. Only 4.0 miles of the same transect 

 were examined in 1965. The 4-mile transect is divided into a northern part 2.1 miles long and a southern 

 part 1.9 miles long. 



In the 1965 survey, 94 live pines from 6 to 37 inches d.b.h. were found to be infected by limb rust, 

 their average diameter being 20.0 inches. The 827 rust-free pines, also 6 to 37 inches d.b.h. , averaged 

 only 11.8 inches. To reflect this major disparity, data in the last three columns of table 1 were recalculated 

 in terms of percentage of basal area as follows: 



Infection class 



North 



South 



Average 





(Percent) 



(Percent) 



(Percent) 



Early 



2.5 



2.1 



2.3 



Intermediate 



6.7 



4.0 



5.4 



Advanced 



14.8 



11.8 



13.4 



Near- lethal 



0.8 



1.4 



1.1 



Total 



24.8 



19.3 



22.3 



The 10 percent of trees that were rusted include about 22 percent of the basal area, with most of the increase 

 over table 1 occurring in the "advanced" infection class. Percentages of volume would show an even greater 

 relative importance of limb rust . 



In the survey transect, there were 30 ponderosa pines that had recently died. They still retained con- 

 siderable bark and most of them were still standing. These were examined for bark beetle galleries, dwarf- 

 mistletoe symptoms, lightning cracks, and, using blocks and stained sections (16), for limb rust mycelium. 



Because blocks could be taken only from near the bottoms of standing trees , limb rust may have es- 

 caped detection in a few trees that had top-crown infections. Nonetheless, limb rust was detected in 22 of 

 the 30 trees. Average diameter of these trees was 20.2 inches, as compared to 16.2 inches for the rust -free 

 trees. Eighty percent of the basal area, consequently, was in infected trees. 



Seven of these dead pines had been poisoned with silvicide to control dwarfmistletoe , and only one of 

 the seven was also rusted; thus 21 of 23 trees (91 percent) that died natural deaths had Umb rust infections. 

 One of the other two was killed by lightning, and the last died of unknown cause. In the northern 2. 1 miles 

 of the transect- -relatively undisturbed forest- -15 of 16 (94 percent) of the dead pines had limb rust 

 infections . 



Of the 23 dead trees not killed by man in the 1965 transect, 9 had been attacked by Dendroctonus bark 

 beetles: 3 by Black Hills beetle (D. ponderosae), 1 by roundheaded beetle (D. adjunctus), and 5 by western 

 pine beetle (D. brevicomis ). Three others may have been attacked: 2 "probably" attacked by red turpentine 

 beetle (D, valens) and 1 "possibly" attacked by western pine beetle (these doubtful galleries were obscured 



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