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County on alert for noxious weeds

FAIRMONT — In an ag-based society, the health of local crops is absolutely vital. To that end, it pays to heed warnings about potentially invasive and noxious plants and weeds.

At the most recent Martin County Commission meeting, Planning and Zoning Administrator Pam Flitter presented the board with some information about two such plants that are causing some concern.

“I went to an ag inspectors conference last week, primarily because during the legislative session there was $300,000 that was given to the [state] Department of Ag,” she said. “That isn’t much per county to be able to implement or continue to do our ag inspector program, but they’re looking at doing it on a grant basis. So this isn’t something you’re going to see right now, it might be this fall or next spring, but I wanted to bring it to your attention.

“One of the reasons why the Legislature was willing to give that portion of money was because there was such an outbreak of a new weed called Palmer amaranth. It has been found in Lyon County and it’s also been found in Iowa, so they’re very concerned about all of us on the Iowa border and having it come into Minnesota. So they are encouraging us counties on the Iowa border to apply for a grant to be able to hire an intern who can do an inventory and at least meet with our township boards and educate them and let them know about this weed.”

She said Palmer amaranth is a noxious weed, and was put on the noxious weed list without even knowing how bad it was actually going to be.

According to the Minnesota Department of Agriculture, the plant is a summer annual that commonly reaches heights of 6 to 8 feet, but can reach 10 feet or more. The green leaves are smooth and arranged in an alternate pattern that grows symmetrically around the stem, with oval and diamond shaped leaves and a small, sharp spine at the leaf tip.

Palmer amaranth competes aggressively with crops, as it has a fast growth rate of 2 to 3 inches per day and commonly reaches heights of 6 to 8 feet, greatly inhibiting crop growth. Yield losses have been up to 91 percent in corn and 79 percent in soybean.

The Department of Ag says the plant is documented in 28 states including neighboring South Dakota, Iowa and Wisconsin, and has been documented in Lyon and Yellow Medicine counties in Minnesota.

Prevention and management are difficult because Palmar amaranth can be resistant to multiple classes of herbicides and their different modes of action. Mowing is not as effective as cultivation, as the plant can regrow from cut stalks and set seed close to the ground. Mowing must therefore be done in conjunction with other methods of control, like herbicide application, to be effective.

The Department of Ag recommends that people prevent all Palmer amaranth plants from producing seed if possible. The plants can be hand weeded and removed for disposal, or if hand weeding is not feasible, people can contact their local University of Minnesota Extension agent, co-op or certified landscape care expert for a specific herbicide recommendation.

Care should be taken to always clean vehicles and equipment after exiting infested areas. If seed was produced, deep tillage will reduce the quantity of seeds that can readily germinate. A cereal rye cover crop can reduce Palmer amaranth germination and growth.

Finally, the plant can be toxic to livestock if the concentration of nitrates in the leaves is high.

“The other noxious weed that’s been put on the list is wild parsnip,” Flitter told the board. “There’s plenty of it around, but I haven’t seen too much of it. The main concern is that there are so many mixes of seed coming in with road construction, particularly with the Department of Transportation.”

The Department of Ag states that wild parsnip is an aggressive, monocarpic perennial plant that germinates from seed and is common throughout the United States. Wild parsnip is highly invasive and if ignored can spread rapidly, developing into large monocultures that replace native animal and plant habitat. It also reduces the quality of agricultural forage crops and can negatively impact livestock if ingested.

One of the main concerns with wild parsnip is the sap. When skin comes in contact with plant sap in the presence of sunlight, it can cause severe rashes, blisters and discoloration of skin. If sap comes into contact with the skin, people should avoid exposure to sunlight, immediately wash skin with soap and water, and seek medical attention. For protection, people are cautioned to wear proper clothing and gloves that protect the skin from contact with the sap.

Mowing or cutting stands larger stands prior to flowering in June will kill a majority of mature plants and significantly reduce seed production. Repeated mowing throughout the season and for several subsequent years is required to prevent re-sprouting and to cut newly bolted plants.

It is recommended that after mowing an infestation, equipment should be washed in order to prevent the movement of seed into new areas.

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