Noxious Weeds | Field 2 Field

May 28, 2020May 28, 2020

Weed of the Month: Tree of Heaven?

Tree of heaven (Ailanthus altissima) is a deciduous tree native to China, Taiwan, and Vietnam. It was brought to the U.S. in the late 1700s as an ornamental shade tree. Today this tree is found in most of the Continental U.S., Hawaii, and Canada. It looks similar to staghorn sumac, ash, and walnut and has a strong, offensive odor that some describe as being similar to rotting peanuts. In 2020, the Minnesota Department of Agriculture changed the regulated noxious weed designation of tree of heaven from Restricted to Prohibited Eradicate, meaning that all tree of heaven plants must be eliminated.

Tree of heaven is fast growing, can reach 90 feet in height, and live 30 to 70 years. This species is highly adaptable and tolerant of disturbance. It is dioecious, meaning there are separate male and female plants. Female plants produce prolific amounts of seed, up to 325,000 seeds per year. Tree of heaven spreads aggressively in response to above-ground cutting or root breaking. Root fragments found in infested soil may start new populations.

*Tree of heaven with mature seeds. Courtesy: Barbara Tokarska-Guzik, University of Silesia, Bugwood.org*

Tree of heaven is the preferred host for the invasive spotted lanternfly (Lycorma delicatula). Spotted lanternfly can attack over 65 tree species, including trees grown in Minnesota. Spotted lanternfly was detected in Pennsylvania in 2014 and has spread to surrounding states over the last several years, but it has not been found in Minnesota.

weed — *An adult spotted lanternfly. Courtesy: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org*

Tree of heaven may play a particularly important role in the spotted lanternfly lifecycle. To date, only two tree of heaven plants have been found in Minnesota, and both populations were eradicated. It is unknown if the absence of tree of heaven will affect the ability of spotted lanternfly to establish in this state. If you suspect that you have found a tree of heaven or spotted lanternfly:

Note the exact location with address or GPS coordinates.
If it is possible, take digital photos of the tree – whole plant, rosettes, flowers, and seed stalks – and suspected spotted lanternfly that can be emailed for identification.
Infestations can be reported to one of two places:
1. The Minnesota Department of Agriculture (MDA) by email at arrest.the.pest@state.mn.us or voicemail 1-888-545-6684
2. Directly to EDDMapS through the Great Lakes Early Detection Network app on a smartphone or tablet.

To learn more about the MDA’s Noxious and Invasive Weed Program and the Noxious Weed Law and Lists, please visit: www.mda.state.mn.us/weedcontrol

August 8, 2019August 8, 2019

Japanese Hops Invading Southeast Minnesota

Japanese hops is and invasive weed that’s overtaking the banks of the Root River in southeastern Minnesota and growing onto adjacent property. Weed experts at the Minnesota Department of Agriculture (MDA) are asking for the public’s help in controlling the weed and reporting new finds.

Infestations are popping up along the Root River from Preston to the confluence of the Mississippi River. Small infestations of Japanese hops have also popped up in Winona; however, these have been controlled.

Japanese hops are annual vines native to eastern Asia that can grow up to 35 feet in a single growing season. With this explosive growth, the vines smother native vegetation and even grow into trees. Leaves are approximately 2-6 inches long and have at least 5 lobes that are shaped like a hand with the fingers extended. There are separate male and female plants that are beginning to flower this time of year. Seed production then follows.

Minnesota is also home to American hops. It is a native perennial vine that looks similar but often has 1-5 lobes and does not have more than 5 lobes on the leaves.

“We don’t know how they got to the Root River; but now that it’s here, we need to work together with the public to control this invasive weed,” said Christina Basch, Noxious Weed Specialist at the MDA. “Since Japanese hops is a prohibited noxious weed on the state’s eradicate list, it’s important that we find infestations and work to get rid of it.”

For successful Japanese hops control, the dispersal of mature seed must be stopped. This can be done by pulling or cutting the vines at the base or with herbicide treatment. Herbicide treatment is the only practical approach for large infestations that can’t be mowed. Experimental torching of seedlings appears to be effective for control of small infestations.

If you find Japanese hops on your land and the infestation is beyond what you can manage, report it to the MDA’s Arrest the Pest line at arrest.the.pest@state.mn.us or 1-888-545-6684. It is helpful to include photos with the report. It is also important to report infestations other than those on the Root River.

Work is already underway to control Japanese hops in the Root River area. Through a grant from the MDA, the Fillmore Soil Water Conservation District and Houston County Planning and Zoning are conducting hops treatments on the Root River banks. Fillmore and Houston County officials, with grants from the Board of Water and Soil Resources Clean Water Fund, are also using Conservation Corps Minnesota (CCM) to control hops along the Root River Trail. The MDA is working with landowners and CCM to control hops on private lands. The MDA’s work to control Japanese hops and oversee the coordinated efforts is supported by the Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizens Commission on Minnesota Resources.

October 5, 2018October 5, 2018

More Palmer Amaranth appearing in SW Minnesota

The Minnesota Department of Agriculture (MDA) is investigating the source of a Palmer amaranth plant found growing in Jackson County.

In early September, a farmer noticed a suspicious weed in the first few rows of a soybean field adjacent to a utility field road. The weed survived a herbicide treatment. making initial identification difficult. The farmer then contacted the University of Minnesota Extension, which submitted the plant for genetic identification. The test has confirmed it was Palmer amaranth. MDA staff scouted fields in the area and have not found any other Palmer plants. The MDA is investigating where the Palmer amaranth seed came from.

“This is another case illustrating the effective collaborations established between the MDA, U of M Extension, crop consultants, and farmers throughout the state for locating and reporting Palmer amaranth,” said Mark Abrahamson, MDA’s Director of Plant Protection. “We continue to urge farmers and landowners to become familiar with what Palmer amaranth looks like and to immediately contact the MDA, Extension, or a crop consultant for help if they suspect Palmer amaranth on their property.”

Since 2016, the invasive weed has now been found in six Minnesota counties. In addition to this latest find in Jackson County, the MDA confirmed the weed in a Redwood County soybean field last week. It was also discovered in conservation plantings in Lyon and Yellow Medicine counties in 2016, and Todd and Douglas counties in 2017. However, after eradication treatments, Palmer has not been found at any sites in those four counties during 2018.

Palmer amaranth is listed as a Prohibited Weed Seed. This means it’s not allowed in any seed offered for sale in the state. It is also on Minnesota’s Prohibited Noxious Weed Eradicate List. All above and below ground parts of the plant must be destroyed. Also, no transportation, propagation, or sale of this plant is allowed.

If anyone suspects Palmer amaranth, they can contact the MDA through the Arrest the Pest line at 1-888-545-6684 or arrest.the.pest@state.mn.us.

Palmer amaranth is native to the southwestern United States and northwestern Mexico. It has been found in over half of the states, and along with Minnesota, it has been found in the neighboring states of Iowa, North Dakota, South Dakota, and Wisconsin.

June 7, 2018

Poison Hemlock Spreading Across Minnesota

Poison hemlock is a toxic member of the carrot family. That’s right, I said carrot family. It can grow to heights of eight feet and has clusters of small white flowers that bloom from May to August. The leaves are fernlike and the stems have purple spots. All parts of the plant are toxic if ingested, which can be especially dangerous to livestock that accidentally eat it while grazing.

2017 was an important year for poison hemlock in Minnesota. Prior to 2017, it was confirmed in isolated pockets of only eight counties. Accurate mapping and reporting led to confirmation of infestations in 17 additional counties across Minnesota, so it is spreading. A rigorous evaluation using a weed risk assessment model, was conducted on poison hemlock by the Noxious Weed Advisory Committee (NWAC).

Based on the results of a risk assessment, any weed species may be recommended for listing on the Prohibited – Eradicate, Prohibited – Control, Restricted, or Specially Regulated categories. After the poison hemlock risk assessment was completed, NWAC recommended that the species be emergency listed as a Prohibited – Eradicate species, the most severe category on the list.

Because of its current status on the Noxious Weed List, landowners are required to destroy all above and below ground parts of the plant. Most infestations are small, with just a few plants. Effective management must prevent seed production and exhaust the seedbank.

Mow before seed set to prevent movement of seed to new locations. Clean equipment, clothing, and shoes after moving through an infestation.
Herbicide applications that target rosettes in the early spring and fall can be very effective. Spring treatments of rosettes should be timed well in advance of flowering and follow-up treatments may be necessary for several years to exhaust the seed bank. If using herbicide treatments, check with your local co-op or certified landscape care expert for assistance and recommendations. There are several businesses throughout the state with certified herbicide applicators that can be hired to perform chemical applications.