1. Blister rust infection is uniformly heavy, ranging upwards from a low 

 average of 10 cankers per tree. 



2. Stand age 25+ years, height 10-30 m, meaning that all trees have been 

 exposed to natural inoculation by the rust fungus for at least 25 years, that they 

 are climbable, and are producing cones. 



3. Stand density open to moderately open, especially in older (50-to 70-year- 

 old) stands, meaning that white pine crowns can be seen or examined with binoculars 

 from some distance. 



Selection of Individual Trees 



1. Candidate trees must be relatively free from blister rust cankers under 

 locally heavy rust conditions. Past experience has shown that under conditions of 

 heavy infrection candidates with one or a few cankers are likely to be just as valuable 

 as those completely free of rust. Thus flexible criteria (allowable number of cankers 

 increasing with local rust intensity) will hold for selecting candidate trees, as 

 follows : 



Maximum allowable infection 

 Rust intensity in the stand per candidate [number of 



(average number of cankers/tree) live or dead cankers) 



10-20 none 



21-40 1 



41-75 2 



76-150 3 



151+ 4-5 



2. Candidate trees should be close to roads so that time and effort is not 

 •wasted in their relocation (by hand compass and pacing) for examination, pollination, 



cone collection, or when revisited for a variety of other purposes. Generally, in 

 denser stands where visibility is limited it is best not to locate candidates more 

 than 100 m from the road. 



3. Runty, seriously deformed (especially multi-forked), seriously diseased 

 (other than by blister rust), or seriously insect-attacked trees should be avoided, 

 because these poor characteristics could be inherited. This includes open-grown 

 trees that are one-fourth or more shorter than surrounding trees of equivalent age 

 and crown class, trees that have repeated stem forks, trees that have several whorls 

 bearing 10 or more large branches, and trees with sinuous or crooked stems not 

 associated with likely mechanical injuries. 



INOCULATION OF SEEDLINGS WITH RUST 



Bingham (1972) reviewed inoculation procedures that have been used for developing 

 blister rust resistant western white pine at Moscow. Briefly, these procedures are 

 as follows: 



7 



