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BACKUS-Pat Bundy, Cass County forester, informed the county board Tuesday about land-based invasive species he studied at a recent seminar he attended in Wisconsin.

Common and Glossy Buckthorn are two European smaller trees that have moved into the area and can spread rapidly. Both like wet or boggy areas and river and pond edges.

They have dark green egg shaped leaves and will grow in sun or shade.

Common buckthorn grows 10 to 25 feet tall. Glossy buckthorn (also called fen or alder buckthorn) grows 10 to 18 feet tall.

They can more easily be identified this time of year, because they retain their green leaves longer than most trees.

They can, however, be confused with dogwoods, plums and wild cherries.

Common buckthorn green to black berries stay on the tree through mid-winter. The red-brown to black Glossy buckthorn berries do not persist.

If you question whether plant on your property are buckthorn or native cherry, plum or dogwood, you can cut a sample and bring to the Cass County Land Department in Backus for identification.

To remove either buckthorn variety, cut the tree at the soil level, then treat the stump with herbicide to prevent re-sprouting. Small seedlings can be pulled by hand and will not re-sprout.

If the infestation covers an area too large to hand pull, you can use a herbicide designed to kill only woody plants and not grasses.

Also covered at the seminar were the emerald ash borer from Asia and the mountain pine beetle.

The ash borer has come into Minnesota from the south. Infestations have been found in southeastern Minnesota, around the Twin Cities and around Duluth. Cut wood cannot be transported by law from these areas in an effort to slow the spread.

Adult beetles have green backs and reddish-purple abdomens. Wings are green. They feed on ash leaves. Females can lay up to 200 eggs in tree bark.

Larvae emerge from under the bark and create serpentine trails in the wood as they eat their way out. They overwinter in the tree sapwood and emerge in the spring as beetles.

Ash trees die because of the extensive cavities the larvae cause in the bark and wood.

The mountain pine beetle has not yet reached Minnesota, but has moved into South Dakota from the West Coast. Moving infested wood, like with the ash borer, has led to its spread.

The beetles prefer stands of densely packed trees. They lay their eggs in the inner tree bark. Larvae feed their over winter and through spring.

Popcorn-like masses of resin appear on the tree trunk when beetle activity begins. Boring dust from the beetles eating the wood begins to appear at the tree base.

Beetles native to Minnesota are less aggressive and typically only infest trees already stressed by drought.

Also discussed was how oak wilt spreads and measures to slow its spread.

It is a non-native fungus. Signs it is present include leaves taking on a bronze to reddish brown discoloration, beginning at the tree top and progressing toward the midrib and base of the leaf. Leaf loss can occur in a little as four weeks.

Wood under the bark turns a bluish-gray.

Oak wilt can spread by connecting roots underground or by beetles carrying it above ground.

Avoid cutting healthy oaks, especially in spring and early summer to prevent spread by beetles. Beetles carrying oak wilt are inactive from November through March.

Oak wilt has moved up from the Iowa border to the southern edge of Crow Wing County.

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