December 2014

The DNR communications team works with agency experts to develop the weekly questions and provide the answers. This feature addresses current DNR issues, interesting topics, or the most frequently asked questions from around Minnesota.


Q: How does the DNR decide whether to aerate a lake to prevent winterkill of fish?

A: The DNR does not aerate lakes, but we do issue permits to lake associations, counties and other local partners who want to aerate shallow lakes that are prone to winterkill due to lack of dissolved oxygen in the water. Public safety is the primary concern, so these permits require aerated parts of the lake to be clearly marked with thin ice signs and located away from high-traffic areas such as boat launches and snowmobile trails.

DNR fisheries and wildlife managers often provide guidance on whether or not aeration is a good idea for a given lake. Some shallow lakes are important habitat for waterfowl, where fish compete with ducks and geese for food while stirring up sediment that can harm aquatic vegetation. In those cases, natural winterkill of fish serves an important biological purpose.

Marilyn Danks, DNR aeration program specialist


Q: When I hiked in the Black Hills of South Dakota recently, I observed the many dying trees related to insect infestation. We take all these precautions when using firewood, but is there cause for concern with Christmas trees being shipped from various places around the nation? It seems like a possible way to spread pests and diseases.

A: You are right to be concerned. According to the lead nursery inspector at the Minnesota Department of Agriculture (MDA), most of our imported Christmas trees are from Michigan and Wisconsin, along with Fraser fir from the Carolinas. Gypsy moth is the main concern on trees coming from those states, and regional inspectors visually check Christmas trees as they come into Minnesota in bulk. The Agriculture Department also conducts spot checks on tree sales lots. The focus of these inspections is proper certification under all applicable state and federal quarantines.

Mountain pine beetle is the insect responsible for killing pines in the Black Hills and in much of the western United States. This insect attacks trees that are 5 inches or more in diameter. Most Christmas trees you’ll find on sales lots are smaller than this. The MDA is considering regulations to prevent the importation of pine wood with bark on it from states where mountain pine beetle occurs. These regulations would be enforced through a state exterior quarantine tentatively scheduled to take effect Jan. 1.

Finally, consider buying Christmas trees grown in Minnesota. That way, you can be sure you won’t be importing an unknown pest.

Val Cervenka, DNR forest health program coordinator


Q: It seems like you see more and more wild turkeys these days near urban areas. Is this just cyclical, or has their population shifted?

A: Turkeys are another species of wildlife that have adapted to living in close proximity to people. Prohibitions on hunting, the relative lack of predators, and the abundant food sources found in urban and suburban landscapes contribute to high reproductive success and low mortality for turkeys and other wildlife.

The preservation of nearby natural areas, including river corridors, wetlands, parks and backyards, provides habitat for wildlife species that many people feel contribute to a higher urban quality of life.

Bryan Lueth, DNR forest wildlife habitat team supervisor


DNR Question of the Week Archive