White pine blister rust (Cronartium ribicola J.C. Fisch.) (WPBR) was discovered on Ribes L. in New York in 1906, although it was accidentally introduced from Europe on pine (Pinus L.) seedlings. The spread of this destructive fungus has changed the forests in North America. After decades of reduced planting because of the concern over the impact of WPBR, white pine (Pinus strobus L.) is now being restored in the lake states of Minnesota, Wisconsin and Michigan. Although the potential for growing white pine is high on many sites, the disappearance of a seed source because of logging and fires means that reestablishment of white pine to these areas will require active management. A series of plantings have been established on three national forests in Minnesota and Michigan to evaluate various silvicultural treatments intended to minimize the incidence of WPBR and to compare the performance of seedlings selected for disease resistance to nonselected planting stock.
M.E. Ostry and P.M. Pijut
Butternut (Juglans cinerea L.) has many fine qualities as a nut species, however, it has never been commercially important. Although the nut is very edible, only a few cultivars have been selected that have desirable nut size and cracking qualities. In the last 20 years there has been a dramatic decline in the number of butternut in native stands caused to a large extent by the lack of natural reproduction and a damaging canker disease. Evidence suggests that superior, disease resistant trees can be propagated and if isolated from areas where the disease is prevalent, may remain disease-free. It is important that the remaining genetic diversity within the species is maintained. Various butternut conservation practices and research projects to restore butternut populations are underway in the United States and Canada.