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Why is my Pigweed Different than your Pigweed? (07/12/18)

Every field season creates interesting observations that reestablishes normal. One observation in 2018 is the redistribution of weeds.

Why is my Pigweed Different than your Pigweed?

Every field season creates interesting observations that reestablishes normal. One observation in 2018 is the redistribution of weeds. For example, prior to 2017, narrowleaf hawksbeard (Latin name = Crepis tectorum) occurred in insignificant areas of fields and along roadsides in western North Dakota, but widespread infestations occurred in Canada and Montana. In 2017, heavy populations and widespread distribution of narrowleaf hawksbeard occurred in ND. You probably have seen it if you live in Williams County. It’s the plant that overwinters in the rosette stage and forms an elongated stem with yellow flowers in the spring. Recently a home owner found a plant specimen identified as narrowleaf hawksbeard in Grand Forks County. How did a weed of the west find its way to the east?

Waterhemp belongs to the botanical Amaranth family, which also features other pigweed species found in North Dakota and Minnesota, including redroot pigweed, Powell pigweed and smooth pigweed. The Latin, or scientific name, of each pigweed includes the genus name Amaranthus; each respective species name differentiates among the genus members.

Waterhemp plants are either male or female (dioecious). Thus, male plants produce only pollen, while female plants produce only seed. This type of biology leads to cross-pollination, or the fertilization of female plants with pollen from one or more male plants. Cross-pollination can greatly increase the genetic diversity of a population, and with genetic diversity comes a wide range of morphological and biological characteristics. Seeds produced by female waterhemp plants are small and usually germinate from very shallow depths in the soil (1/2 inch or less). The number of seeds produced by female waterhemp plants can vary depending on many factors. Waterhemp has been a ‘game-changer’ due to its wide period of germination and emergence and due to its herbicide resistance.

Most Agriculturalists associate waterhemp with the eastern portion of the state of North Dakota or areas east of US 281. However, in 2018, waterhemp has been identified in central and western areas of North Dakota. Recently a homeowner from Beach, ND sent a sample that was identified as waterhemp. Once again, how does a pigweed that is common in the east find its ways to the Beach, ND, one of the most westerly communities in North Dakota?

How do weeds spread? They spread by natural methods including wind, water and by animals and by humans by vehicles, attached to equipment such as combines or tillage and in contaminated seed or feed. Following the 2107 drought, numerous quantities of hay baled in places like Wisconsin, Kansas and Nebraska were shipped to North Dakota. While the intent was positive, it is possible that donated and purchased hay contained weeds and weed seed. Dare I say the hay may contain Palmer Amaranth, a weed we don’t yet have in ND….

We remind you to be curious about the weeds you observe in your gardens, in your agricultural fields or in your pastures. Ask for assistance is weed identification if a weed such as pigweed doesn’t look like other pigweeds in your community. Call your County Agent, ask your crop consultant or ag-retailer. Call a State Specialist. But, above all, be curious. We intend to continue our campaign about Palmer amaranth awareness and identification. Palmer amaranth will start flowering soon if it accidentally was transported to North Dakota. We will teach you how to identify it and assist you in its eradication if we find it. As we have stated, we don’t have Palmer Amaranth in North Dakota and we don’t’ want it.

 

Tom Peters

 Extension Sugarbeet Agronomist

NDSU & U of MN

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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