June 2006





The DNR, Department of Agriculture and U.S. Forest Service are preparing to combat a gypsy moth outbreak later this summer along Minnesota's North Shore. How will gypsy moths affect Minnesota trees?

Although there is an infestation along the North Shore, the county will not likely be declared permanently infested for a number of years. Once a county is declared permanently infested with the gypsy moth, it commonly takes five to 10 years before population numbers are high enough to be noticed by the public. Once that point is reached, however, gypsy moths will defoliate many hardwood trees, particularly oak, aspen, birch and basswood. In that regard, gypsy moth outbreaks will resemble forest tent caterpillar outbreaks. But the outbreaks will last longer and be more severe because Minnesota lacks the natural enemies needed to control this invasive species. Most trees can withstand some defoliation. If defoliation occurs two or more years in a row, tree mortality is likely. Trees most at risk of dying are those that are already stressed by some other factor, such as construction damage or severe drought. The best way to limit future damage is through proper tree selection, site preparation and tree care.

Susan Burks, DNR Forest Health Specialist


What is the purpose of native aquatic plants along a shoreline?

Aquatic plants are essential components of most freshwater ecosystems. Many of Minnesota's most sought-after fish species depend heavily on aquatic vegetation for food, protection from predators and reproduction. In addition to fish, many wildlife species depend on aquatic plants for food and nesting sites. Aquatic plants not eaten directly by waterfowl support many insects and other aquatic invertebrates that serve as important food sources for migratory birds and their young. Emergent aquatic vegetation also provides nesting cover for a variety of waterfowl, wading birds, shorebirds and songbirds. The reproductive success of ducks nesting near lakes, for example, is closely tied to the availability of aquatic plants. Beyond providing food and shelter for fish and wildlife, aquatic vegetation maintains water clarity, prevents suspension of bottom sediments and limits shoreline erosion by moderating the effects of wave and ice erosion. A healthy native plant community also prevents the establishment of non-native invasive aquatic plants. In short, many of the things that we enjoy most about lakes are directly linked to aquatic vegetation.

Steve Enger, DNR Aquatic Plant Management Program coordinator


With slot limits on nearly every Minnesota lake it is important for anglers to know the fish they keep are of legal size. What is the proper way to measure a fish?

An accurate measurement of your catch may be difficult for a number of reasons. The boat may be pitching and rolling on the lake. Fish are slippery creatures that do not like to lie still. And, there are obstacles in the boat like hooks, tackle boxes and other anglers. However, accurately measuring any fish caught helps sustain fish populations and provides other anglers the same opportunities you just enjoyed. To properly measure a fish, anglers should use a ruler affixed to a flat surface with an "end stop" at the zero end of the ruler. Lay the fish over the ruler with the nose pressed against the end stop. Pinch the tips of the tail together. The length of the fish from nose to the tip of the tail is considered the legal length of the fish. While in rough water, the end stop acts as a measurement aid, preventing the fish from sliding around on the ruler. Flexible tape measures do not provide an accurate length.

Maj. Al Heidebrink, DNR Division of Enforcement


The emerald ash borer, an invasive species, may soon arrive in Minnesota. How will this insect impact Minnesota trees?

Unlike the gypsy moth, which defoliates trees but does not necessarily kill them, the emerald ash borer is capable of killing healthy ash trees all by themselves. That makes them potentially much more damaging then the gypsy moth. While the emerald ash borer seems to prefer green ash, they are capable of killing all species of ash within two to three years of attack. The insect can also affect ash within all forest types. Ash trees were planted in abundance throughout the state after Dutch elm disease took out so many mature elm trees. Ironically, those trees are now at risk of attack. Local communities face a potential crisis in tree protection, removal and replacement. Public funds are inadequate to address the issue. However, people can help by: buying firewood locally rather than bringing it with when camping, burning it all before leaving the camp site and checking with firewood suppliers when buying wood for the home to make sure it is certified pest free. To report any suspected invasive pest, contact the local DNR, Department of Agriculture or University of Minnesota Extension agent office.

Susan Burks, DNR forest health specialist


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