(Castanea dentata) in Ontario - Ministry of Natural Resources ...

Recovery Strategy for the American Chestnut in Ontario
new American Chestnut trees. There are also ongoing programs of habitat restoration
that will benefit American Chestnut and other Carolinian species.
1.6 Threats to Survival and Recovery
The following threats to survival and recovery of American Chestnut are listed in order
of importance:
Chestnut Blight
Chestnut blight is the single greatest threat to American Chestnut in Canada. The blight
was first noticed at the Bronx Zoo in 1904 on nursery stock, but it likely had multiple
introductions at that time. The introduction of chestnut blight, caused by the fungus C.
parasitica (Murrill) M.E. Barr, devastated the American Chestnut species throughout
North America including Ontario. American Chestnut has persisted in southern Ontario
by resprouting from the collars of surviving root systems but regenerated sprouts
continue to become re-infected by the fungal pathogen. Some trees in southern Ontario
are not currently showing blight symptoms. McKeen (1985) reported that 50 percent of
trees had no obvious blight and Melzer and Boland (2004) found 41 percent of trees to
be free of disease symptoms. In the most recent survey (Tindall et al. 2004), 325 of 459
trees assessed for blight (71%) had no obvious blight symptoms.
Chestnut blight will continue to threaten the remaining small and isolated populations of
American Chestnut because it survives on sprouts and on alternative hosts.
Cryphonectria parasitica has been observed to kill some alternative hosts but it usually
exists on these hosts as a weak pathogen or saprophyte. Alternative hosts of C.
parasitica in the Carolinian zone of southern Ontario include: White Oak, Red Oak,
Black Oak (Q. velutina), Red Maple, Staghorn Sumac (Rhus typhina), Shagbark
Hickory, Bur Oak (Q. macrocarpa), Chinquapin Oak (Q. muhlenbergii), Hop Hornbeam
(Ostrya virginiana), Blue Beech (Carpinus caroliniana), Tulip Tree (Liriodendron
tulipifera) and Sassafras (Sassafras albidum) (Mooij 1997). Locations for new plantings
of American Chestnut for restoration or nut crops should be chosen carefully as they
may act as a bridge to connect diseased populations of American Chestnut to isolated
populations that have escaped disease.
Loss of Individuals
Loss of individuals due to clearing of forests for farming and development continues to
be a threat to American Chestnut in Ontario. Several sprout clumps of chestnut occur
along roadsides and are repeatedly cut back or sprayed with herbicide so they will not
interfere with overhead wires. Several young trees/sprouts have been damaged or
killed due to logging and others have been lost due to clearing of forests and fencerows
for agriculture and urban development. While many rural land owners practice good
forest management and stewardship, exceptions of poorly managed forests including
unsustainable logging and even complete clearing to expand other economic activities,
are having a negative impact.
9