1. Inoculate seedlings after the second growth period. The t>'pical 2-year-old 

 seedling is about 10 cm tall, has mostly secondary needles with a few remnant primary 

 leaves. Much of the resistance is in the secondary needles; therefore if 1-year-old 

 seedlings were inoculated many mechanisms of resistance would be missed. 



2. Use natural inoculum from several sites and thoroughly mix the infected 

 Ribes leaves before placing them over the seedlings. This will assure a good mixture 

 of rust races. 



3. The Ribes leaves are layered on wire screening 30-40 cm above the seedlings. 



4. Humidity is kept as near 100 percent as possible and the temperature 

 between 15°-20°C. This is achieved by either enclosing the set-up with plastic that 

 is shaded by canvas (Bingham 1972) or by layering wet burlap over wire screens 

 (Patton and Riker 1966). Maintain test conditions for 72 hours. 



In the Moscow, Idaho, environment seedlings are inoculated during the first 2 

 weeks of September. 



RUST INSPECTION 

 First Rust Inspection 



Timing: In Moscow, Idaho, environment, June, 9 months after inoculation. 



Criteria: Count needle spots on secondary needles of each seedling by color 

 type, on uppermost two fascicles and measure length of fascicles. This sampling 

 method depends upon attaining at least 8 spots per lineal meter of needles. If it is 

 much less, this sample will be inadequate and either more fascicles should be added 

 to sample or all the spots on the tree counted. Adding more fascicles adds a lot of 

 time and counting all spots decreases precision, so a strong effort must be given to 

 the inoculation procedure to make sure that an adequate number of spots are produced. 



Second Rust Inspection 



Timing: In Moscow, Idaho environment, September, 1-year after inoculation. 



Criteria: Determine the presence of needle spots on secondary needles plus stem 

 symptoms of each seedling. Four major stem symptoms are: normal cankers; small 

 circular, shallow necrotic areas of sunken bark associated with the base of a single 

 needle bundle; shallow or deep necrotic areas in the needle portion of the seedling 

 stem that partially encircle the stem; shallow or deep necrotic areas in the needle 

 portion of the seedling stem that completely encircle the stem. 



Third, Fourth, and Fifth Rust Inspections 



Timing: In Moscow, Idaho, environment, September, 2, 3, and 4 years after 

 inoculation. 



Criteria: Determine the presence of stem symptoms as listed under second rust 

 inspection plus health of each seedling. 



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