No abstract

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.

No abstract

In the northern Rocky Mountains, whttebark pine (Pinus albicaulis) is rapidly declining as a result of previous fire exclusion policies, mountain pine beetle (Dendroctonus ponderosae) outbreak$ and white pine blister rust (Cronartium ribicola). Blister rust is potentially the most destructive ageng killing seedltng~ cone-hearing branche$ ana~ eventually, mature tmex We examined densities of whttebark pine regeneration and the incidence and severity of blister-rust infection of seedlings and saplings in the 25-year-oid Sundance Burn in the Selkirk Range of northern Idaho, an area heavily infected by blister rust We found that the mean regeneration density of whitebark pine was significantly lower than that of two other comparably aged burns in western Montaruz The low density was attributed to the severe damage to the seed source on the burn perimeter, resulting from previous infestation of mountain pine beetle and blister rust. Overal~ 29% of the whttebark pine regeneration in the Sundance Burn was infected by blister rust Age and height of seedlings were important predictors of incidence of infection, and height was the most important predictor of severity of infectior~ Thu.~ us seedlings grow larger, they present a bigger target to airborne blister-rust spore£ Because of the lack of seed production in the adjacent forest and expected mortality, regeneration of whitebark pine in the Sundance Burn will be slow. In areas of northern Idaho and northwestern Montana affected by blister rust and pine beetle, prescrihed fires for managing whitebark pine ecosystems should be restricted to small areas or should require plantings of rust-resistant seedlingx Los efectos de Cronartium ribicola en la regeneraci6n de Pinus athicaults posterior al incendio: El krea quemada de "sundance" en el Norte de Idaho. Conservation Biology, Pages 654--664 Volume 9, No. 3. June 1995 Tomback et al. Blister Rust and Forest RegeneratJon 655de montaFta y del ttz6rt En totag un 29% del drea de regeneraci6n de Pinus albicaulis en "Sundance Burn" fue infectada por el tiz6r~ La edad y la altura de los retoFtos fueron importantes predictores de la incidencia de la infecci6n y la altura rue el predtctor mds importante de la severidad de la infecci6rL Asg a medida que los retoFtos crecen en altura, presentan un blanco mds prominente para las esporas del tiz6rt Dada la falta de producciOn de semillas en el bosque adyacente y la mortalidad esperada; la regeneraci6n de Pinus albicaulis en "'Sundance Burn" va a ser lenta En las dreas del norte de Idaho y noroeste de Montan~ afectadas por el tiz6n y el escarabajo de la pino, los fuegos prescriptos para el manejo de los ecosistemas del pino de corteza blanca deben ser restringidos a dreas peq~ o deben requerir la plantaci6n de retotios resitentes al tiz6rL