Biology And Management Of Waterhemp And Palmer Amaranth

At 2:30 p.m., Joe Ikley will be discussing information on waterhemp and palmer amaranth at the Williston Hard Spring Wheat Show.

Dr. Ikley is the new North Dakota State University Extension Weed Specialist. He has conducted research on both palmer amaranth and waterhemp for six years in Indiana, and waterhemp for one year in North Dakota.

Ikley will be talking about the biology and management of palmer amaranth and waterhemp. "The main message will be that we do not want either weed in western North Dakota, as they can be both troublesome and expensive to control. Examples of problems caused by waterhemp in eastern North Dakota will be presented to highlight some of the challenges these weeds can present once they become established in an area," explained Ikley.

Palmer amaranth and waterhemp have both been found in North Dakota, but neither is established in western North Dakota. "These weeds are a different monster than our more traditional pigweeds when it comes to effective control. Prolific seed production, long emergence periods, and high propensity to evolve resistance to herbicides compared to other pigweeds make palmer amaranth and waterhemp more difficult to control. They also have a more rapid growth rate, which makes timeliness of an effective herbicide application critical for the overall management of these two weeds," stated Ikley.

Ikley has been a part of research that evaluated the growth rate and seed production capabilities of palmer amaranth and waterhemp weeds in Indiana. He has also assessed their control with currently available herbicide programs in corn and soybean.

The goal of his research has been to understand the biology of these weeds and how to control them with currently available herbicide tools. "Unfortunately, we are several years away from the potential for any new herbicides to control these weeds, so now the effort has to shift to integrating tactics, such as cover crops or Harvest Weed Seed Control, to preserve the herbicides we currently have and avoid widespread herbicide resistance in North Dakota," said Ikley.

In the future, Ikley will be evaluating the effectiveness of cover crops in eastern North Dakota for the suppression of waterhemp. "Southern states in the U.S. have evaluated the capability of cover crops for suppression of waterhemp and palmer amaranth, but we do not have any data from North Dakota where we often cannot produce the high levels of cover crop biomass that southern states obtain annually. I will also be evaluating when seed-shed occurs in waterhemp in North Dakota to determine if Harvest Weed Seed Control options, like the Harrington Seed Destructor, can work on waterhemp in North Dakota. This type of weed seed control is most viable on plants that have seed attached at harvest, and we do not know how much waterhemp seed is still attached to mother plants at harvest in North Dakota."

When asked what he would suggest to growers who deal a lot with these weeds, he responded, "Rotation of crops and herbicides remain some of the most important tactics for control of waterhemp and palmer amaranth. Practicing good agronomy, particularly in soybean, really help with control of these weeds. Crops that struggle to achieve a crop canopy are vulnerable to late-season populations of waterhemp or palmer amaranth. For those who do not deal with a lot of waterhemp or palmer amaranth, prevention is one of the best practices we have. Hand-weeding a few plants that have popped up in a field can save a lot of headache in future years if those plants are allowed to produce seed."