by: Tony Duke & Ed Baily
JUNE 1983
The current budworm outbreak on the highlands of Cape Breton is not only killing trees, it's slowing down the ability of the forest to regenerate itself. every year since the outbreak began in 1973, the budworm caterpillars have eaten needles from the old trees so that today 2/3 of the merchantable balsam fir trees are dead. And the highland forest is mostly balsam fir.
The other loss results from the budworm feeding on the flowers of the remaining living trees. In fact, the flowers of fir and spruce are the preferred food of the budworm- no flowers mean no seed. Without seed the forest will not regenerate itself.
For about fifteen years foresters have been experimenting with planting trees on the highlands. The main lesson they have learned is that the trees have to be specially adapted to the severe conditions. In some instances seedlings grown for our regular planting program do well - until they grow above the snow. The tops then die, because they cannot stand the drying winds of spring while the roots of the tree are still frozen in the soil. In other instances, early or late frosts cause damage to the new shoot growth resulting in a stunting of the seedlings growth.
Tree species that grow on the highlands, although the same as those at lower elevations, are genetically different, and have adapted to the unique climate conditions. So any trees we plant have to first be adapted to the climate. The second important criterion is that it must be a species that is unpalatable to the budworm.
If you fly over the highlands, the areas of green among the grey are pockets of black and white spruce among the dead balsam fir. These two species are more resistant than fir to budworm attack and are adapted to the climate; so are the obvious choice for replanting. But since the destruction of flowers has severely limited the seed supply we had to turn to another method.
For black spruce vegetative propagation is that method. It means starting young trees from parts of older ones. In 1978 and 1979, a small quantity of highland black spruce cones which fortunately escaped destruction by the budworm were located and collected. The seed was extracted, grown in the greenhouse and after a year of growth the top two inches of the shoots were cut, the needles removed from the lower third of the cuttings and each cutting was placed in its own container. After about 8 weeks the cuttings were fully rooted and began to grow. These new trees will be ready to plant on the highlands when they are eight inches tall.
We have now rooted over two million cuttings. But it's more costly than growing trees from seed. Original plans called for reforesting approximately 2/3 of the highlands with black and white spruce at the rate of 5,400 acres a year. Because vegetative propagation requires more greenhouse space, the annual program will be somewhat reduced at least until budworm populations decline and seed from protected highlands sources is again available.
These plantations are expected to mature at age 40 and yield close to 30 cords per acre. For comparison, natural unmanaged stands on the highlands yield an average of 25 cords at approximately 60 to 70 years of age.
We're still searching for seed that will give us trees adapted to the highlands and resistant to budworm. At present we have experimental plantings of spruces, pines and larch from China, Germany, Sweden and Newfoundland as well as Cape Breton. We are also protecting the seed source we have on the highlands by spraying the trees each year with the bacterial agent Bacillus thuringlensis (Bt.). While this had protected the foliage, it has largely been unsuccessful in protecting the flowers. The surviving population of caterpillars, even though small, quickly destroys them.
This highland reforestation program is part of an overall forest management program in the recently signed Forest Resource Development Agreement. Its goals are to increase the diversity of the forest and to offset wood shortages caused by the catastrophic losses to the budworm and the lack of forest management in the past.