Figure 7. — Aspen sprout 

 browsed off to about 14 

 inches high. There were 

 an average of 653 sprouts 

 per acre on sample plots, 

 but most were overtopped 

 by forbs as is shown in 

 this photo. Although 

 aspen sprouts were 

 present on 96 plots, 

 they were actually 

 replacing dying trees 

 on only three plots; 

 all other aspen sprouts 

 were held in check by 

 browsing and pest 

 damage. 



incidence of disease and insect problems in stems expressed as a percentage of the 

 aspen tree sample (n=4,016) is shown in the following tabulation: 



Plot 



Problem Causal organism incidence 



Bark wounds Big game and rodents 90.0 



Stem-boring insects Agrilus spp. 2 27.0 



Cytospora canker Cytospora chrysosperma 25.0 



Sooty bark canker Cenangium singulars 14.7 



Cryptosphaeria canker Crypt osphaeria populina 2.0 



Heartrot Pomes igniarius 1 . 2 



Ceratocystis canker Ceratocystis fimbriata .6 



Rough stem galls Diplodia tumefaciens 2 .3 



Roundheaded borer galls Saperda sp. 2 .2 



Buttrot Pomes applanatus .1 



do. Pholiota squarrosa .1 



Identified by symptoms only. 



9 



