Relative blister rust resistance of white pines

The frequency of six mechanisms of resistance to white pine blister rust is presented for 18 white pine species. The mechanisms are: prevention of needle lesions, reduced frequency of such lesions, premature shedding of infected needles, a fungicidal reaction in the short shoot, reactions that eliminate established bark infections, and the ability of a seedling to remain alive when infected. The importance of these mechanisms in selecting for resistance in the very susceptible North American white pines is discussed.