Saving the Butternut Tree: Intervention

A stem canker on a young butternut, indicating an area under the bark where the cambium has been killed. Photo © Barb Boysen

By Barb Boysen

For disease-threatened species, conservation is just the first step. FGCA could protect every tree and still lose the species—active intervention is often necessary. Thinning the forest to increase sunlight can improve a butternut’s vigour and strengthen its ability to produce seed. Seed collection and tree planting can help keep butternut on the landscape. In this way, genetic diversity is maintained, providing more time and options to find genetic tolerance.

Intervention can also involve cloning, breeding, and reintroduction. Trees that may be genetically tolerant will have little canker or can quickly callus (i.e. seal off) the canker. However, these rare trees can be distant from each other with little chance for the cross-pollination needed to pass these genes on to the next generation. The situation is exacerbated in areas of little forest cover. The University of Guelph Arboretum’s Elm Recovery Program calls itself a ‘dating service’ for lonely elms that have survived Dutch elm disease. Similarly, FGCA is monitoring surviving butternut and bringing them together through cloning and archiving. Finally, butternut’s naturally short lifespan gives an urgency to finding and cloning these trees.

The five-year goal is to graft 10 trees that may be genetically tolerant from each of the many ecologically unique areas across southern Ontario. Initially, butternut archives will be managed to produce seed. As researchers develop canker screening methods, the grafts will be tested to hopefully prove genetic tolerance. The next step is a breeding program to ultimately introduce tolerant butternut across southern Ontario.

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