November 2007

Date

Question

Answer

11/27/2007

Given the extremely dry summer we had followed by a wet fall, should we still prune our trees if they need it? If so, when?

Good question. If they are already showing signs of decline as a result of the drought, it's best to wait on any pruning activities - because although pruning is good for trees, it is a temporary stressor, and on top of severe drought, stress may be enough to invite in secondary pests like the two-lined chestnut borer that loves stressed oak trees.

Signs of decline would be late spring leaf-out, early fall color, branch die-back in the tree tops, smaller than usual leaves and/or pale colored leaves. If these symptoms are present, I'd wait to see if the trees can increase their vigor before being pruned.

If the trees are vigorous with no signs of stress, and have normal color, normal growth, etc, then pruning is fine. The best time to prune is during the winter when trees are dormant. But it's hard to tell what's live wood and what's dead wood during the winter. Pruning in fall is the next best time to prune. Spring is the worst time to prune because the bark is loose and injures easily and because disease agents are in full swing during those cool wet months.

- Susan Burks, Minnesota DNR forest health specialist

11/20/2007

Duluth is known as an area for a high concentration of hawks in the fall. Why?

Many migrating birds, including raptors and passerines, concentrate in impressive numbers at the western tip of Lake Superior. Some travel from as far away as the Arctic and pass through Duluth on their way to their wintering areas to the south. Reluctant to cross a large body of water, migrants funnel down the North Shore along the ridges that overlook the city. Flyway patterns often follow coasts of large bodies of water for this reason.

- Lori Naumann, DNR nongame wildlife information officer

11/13/2007

Late summer and early fall large numbers of loons were recently spotted gathering on a number of lakes. However, they were not feeding and not fighting; they appeared to be partying. Why is this? Is this part of the fall migration?

Loons are territorial when they are nesting and raising chicks. But starting in mid-summer, groups of non-mated loons, or loons that were unsuccessful with nesting, begin to gather and move around between lakes. I call these groups "loon parties" because they are indeed socializing and not fighting. Sometimes the loons will circle and actively interact.

As the summer wanes on, these groups get larger and blend into the pre-migratory behavior of gathering on larger lakes. In September, many adult loons that successfully raised chicks leave those lakes, and their chicks, to join the loon groups. In 1998, loon counts completed on Mille Lacs and Winnibigoshish lakes documented a peak of more than 1,500 loons on each lake in the third week of October.

On Oct. 19, 2006, a new high count of 2,729 loons on Mille Lacs was reported by Peder Svingen, a birdwatcher from Duluth.

These groups are comprised of adult loons and young-of-the year. After gathering on these larger lakes, the loons head south on a north wind in late October or November. Loons spend the winter on the ocean and young loons will remain there for two or three years before returning to Minnesota.

- Pam Perry, DNR nongame wildlife lake specialist, Brainerd

11/06/2007

Given the extremely dry summer we had followed by a wet fall, should we still prune our trees if they need it? And when?

Good question. If they are already showing signs of decline as a result of the drought, it's best to wait on any pruning activities. Although pruning is good for trees, it is a temporary stressor, and on top of severe drought, stress may be enough to invite in secondary pests like the two-lined chestnut borer who loves stressed oak trees.

Signs of decline would be late spring leaf-out, early fall color, branch die-back in the tree tops, smaller than usual leaves and/or pale colored leaves. If these symptoms are present, I'd wait to see if the trees can increase their vigor before being pruned.

If the trees are vigorous with no signs of stress, and have normal color, normal growth, etc., then pruning is fine. The best time to prune is during the winter when trees are dormant, but it is difficult to tell what's live wood and what's dead wood during the winter. Pruning in fall is the next best time to prune. Spring is the worst time to prune because the bark is loose and injures easily and because disease agents are in full swing during those cool wet months.

- Susan Burks, Minnesota DNR forest health specialist

 

DNR Question of the Week Archive