Most Common Topics

Invasives

Emerald Ash Borer

According to the Wisconsin Department of Natural Resources, Emerald Ash Borer (Agrilus planipennis) is an invasive wood boring beetle that feeds on the tissues under the bark of ash trees and kills them. The metallic green beetle, which is smaller than a size of a penny, originated in East Asia and was inadvertently imported to the United States inside wooden shipping crates from China.  It was first discovered near Detroit, Michigan in 2002. Since then, Emerald Ash Borer has spread to over a dozen states and Canada. While Emerald Ash Borer is not a threat to human health it does threaten forest and urban tree populations.

Land owners and residents should be on the lookout for possible Emerald Ash Borer symptoms. The Wisconsin DNR reports that infected trees may begin to show damage beginning with dieback at the crown of the tree. Since the Emerald Ash borer larvae block the trees' nutrients, dead branches and loss of foliage may begin to appear. When trees are stressed, they may also begin to grow epicormic branches and sprouts at the base of the trees. In addition to bark splits, increased woodpecker activity can also be a warning sing that a tree is infected. Woodpeckers eat the Emerald Ash Borer larvae and the “flecking” of large strips of bark may appear.  

Once infected, Emerald Ash Borer can kill a tree within three years and sometimes as little as one year. It is important that the necessary steps be taken to help prevent the spread of Emerald Ash Borer. A statewide effort to discourage the movement of firewood has been the main thrust of public education efforts since the beetle tends to hitchhike on firewood. For woodlot owners, the DNR offers several tips on how to manage their woods to prepare for the Emerald Ash Borer invasion:

• Until Emerald Ash Borer is found in the local area, continue regularly scheduled harvests. 
• In stands where ash forms 20% or more of the basal area, reduce the ash component during regularly scheduled thinning or harvesting.
• When selecting ash trees to thin, first remove those that have low vigor and quality, maintain dominant and co-dominant ash trees with good form/health, and remember to follow the stocking guidelines for your forest type.
• During regeneration activities, promote species other than ash. In certain stands, this may require cutting or herbicide use on ash regeneration. The goal should not be to eliminate ash. Try to keep ash regeneration to 10% or less of all regeneration.

Some good news has emerged in the effort to fight off the Emerald Ash Borer. A native wasp in Michigan was shown to eat the larvae of the Emerald Ash Borer and it is hoped that more native insects will be discovered to aid in the reduction of Emerald Ash Borer populations.

Garlic Mustard

Originally introduced to the United States in the 1800s from European settlers who used it for medicinal and food purposes, garlic mustard is just one of dozens of invasive species in Wisconsin. However, what sets garlic mustard apart from other invasive species, is the determination and persistence needed to remove the plant and the difficulty in stopping the spread of the troublesome plant.

According to the Wisconsin Department of Natural Resources, garlic mustard grows in upland and floodplain forests, savannas, yards, and along roadsides. The plant is shade-tolerant, and generally requires some shade and is not commonly found in bright or sunny habitats. The invasion of forests usually begins along the edge of the woodlands and spreads via roads, paths and trails. Fur bearing animals including deer, horses and squirrels also can spread garlic mustard.

Garlic mustard is a biennial plant that has two different growth patterns. During the first year of growth, the plants are low growing and form clusters of leaves with rounded and scalloped edges. In the second year of growth, garlic mustard can grow to be one to four feet in height and spawn white flowers. Garlic mustard blooms in southern Wisconsin from May through early June and fruits begin to ripen in mid-July.

Once garlic mustard is discovered, it can be very difficult to remove. It is important to tackle the plant as soon as spring arrives as garlic mustard seeds germinate in early April once snow has melted. According to the DNR, the first-year garlic mustard plants remain green throughout the winter, which can make spotting and removing the plant easier.

If garlic mustard is not dealt with, it can take over a forest in as little as ten years. There are two ways to combat the plant; either chemically or mechanically. If you decide to take the chemical approach, it is important to do so in the early spring. Since garlic mustard grows as soon as the temperature rises above freezing, it’s often one of the first plants out of the ground. Products containing the chemical glyphosate can help eradicate garlic mustard but it’s important to remember that the chemical shouldn’t be overused. Glyphosate isn’t discriminatory in the plants that it kills so be cautious as to not eradicate surrounding non-invasive plants.
Those who wish to stay away from chemicals can take a mechanical approach. Simple hand pulling of the plant can be very affective. Pull as close to the ground as possible to make sure to remove the plant with the roots. The most successful time to pull the plant is in early spring. If done before the early flowering stage, the DNR has found that it resulted in 99 percent mortality and eliminated seed production.
To help identify garlic mustard, or any other type of plant on your property, the University of Wisconsin-Madison offers a weed identification tool that can help landowners identify unknown weeds and plants on their properties. It can be found by visiting http://weedid.wisc.edu/weedid.php.