

IHtUKCl ILrtL 



ur\^> j. *-> 



TAXONOMY, CROSSABILITY .AND RESISTANCE OF WHITE PINES 



273 



localities; 220 + P. peuae in 10 localities; and many thousands of P. 

 strobus trees in more than 100 localities. Spaulding's (1925, Table 1) 

 ratings of "Immune, Resistant, Susceptible, and Very Susceptible" are 

 here merely ranked 1, 2, 5, and 4, respectively. Questionable rankings 

 are given where Spaulding (1925) indicates the tree basis is weak. 



Hirt, 1940: Hirt's observations were made on two field plots at 

 Warrensburg and Syracuse, New York. Seedlings of the white pine species 

 were planted in a systematic mix and exposed to natural inoculation by 

 rust spreading from planted Rites nigrum L. bushes. After a single 

 season's exposure seedlings were lifted and held elsewhere for develop- 

 ment of rust symptoms. Groups of from 44 to 100 seedlings each of 3-7 

 species were exposed in experiments undertaken in four different years. 

 Intensity of infection was stated in terms of percentage of trees 

 infected, numbers of cankers per infected tree, or cankers per 1,000 

 inches of needlage. Seedlings actually tested included: 68 P. aristata 

 seedlings exposed for 2 seasons; 83 P. cembra for 1 season; 258 P. flexilis 

 for 3 seasons; 72 P. kovaiensis for 1 season; 174 P. montioola for 4 

 seasons; 322 P. peuae for 4 seasons; 56 P. strobiformis for 1 season; 

 and 351 P. strobus for 4 seasons. Rankings given in Table 2 were obtained 

 by assigning the lowest infection level (of all 3 measures of infection) 

 the rank 1; the highest infection level, the rank 8; then, by arith- 

 metically averaging the rankings. 



Bedwell and Childs, 1943; and Childs and Bedwell, 1948 : Bedwell 

 and Childs reported upon levels of natural infection (cankers per thousand 

 needles) in 159 pairs of P. albicaulis and P. monticola trees (heights 

 ranged from 5 to 11 feet) growing together in 8 Idaho, Washington, and 

 Oregon natural stands; also, these authors reported upon natural infec- 

 tion of 355 P. albicaulis and 1,077 P. monticola seedlings that were 

 growing together in a Garabaldi, British Columbia, nursery. Later, 

 Childs and Bedwell (1948) reported upon natural infection found on 7 

 experimental plots established in British Columbia and Oregon, mostly 

 with 4-year-old nursery stock. Infection intensity, stated in terms of 

 number of cankers per million seedling needles, was determined 5 to 10 

 years after outplanting on: 255 P. aristata trees located on 3 different 

 plots; 42 P. avmanalii on 2 plots; 538 P. flexilis on 5 plots; 229 P. 

 griffithii on 2 plots; 109 P. kovaiensis on 1 plot; 447 P. lanbertiana 

 on 4 plots; 1,946 P. monticola on 7 plots; 369 P. peuce on 3 plots; 241 

 ?. strobiformis on 3 plots; and 725 P. strobus on 5 plots. In addition, 

 Childs and Bedwell observed natural infection on 4- to 40-feet-tall 

 white pines in a Carson, Washington, arboretum, there examining 20 P. 

 aristata, 2 P. armandii , 24 P. flexilis, 19 P. griffithii, 20 P. koraiensis 

 11 P. lambertiana, 21 P. monticola, 22 P. parvi flora, 3 P. peuae , 30 P. 

 strobiformis, and 8 P. strobus trees. Rankings of Table 2, column 4, 

 for the nursery and field plots or stands, come from converting the 

 lowest level of cankers per million needles to rank 1, the highest to 

 the highest numerical rank. For the Carson arboretum trees, rankings 

 are in the order of susceptibility given by Childs and Bedwell. 



Meyer, 1954 : Meyer's observations are the most limited, coming from 

 natural infection of single trees of 7 white pine species growing in a 

 Hann. Mtlnden, Germany, arboretum. The 20+-year-old trees were classified 

 merely as without infection, or as weakly, moderately, or heavily infected. 

 In Table 2 rank 1 applies to noninfected trees; ranks 2, 3, and 4 apply 

 to the weakly, moderately, and heavily infected trees, respectively. 



