Palmer amaranth discussed

By Anna Smith - Preble SWCD

EATON — On Tuesday, Nov. 28, 2017, Preble Soil and Water Conservation District hosted a noxious weed meeting at the Eaton First Church of God. The focus of the meeting was the extremely destructive weed, Palmer amaranth, which was found in Preble County earlier last year.

This weed is far more destructive than any other local weed due in part to its rapid growth, resistance to several classes of herbicides, and ability to produce over 500,000 seeds per plant. The weed is being spread from southern and western states primarily through livestock feed, though now that it is in Preble County, it will likely spread through other methods including farm equipment.

The meeting began with Preble SWCD staff outlining the discovery of the weed in Preble County. To date, it has been found in three separate locations across the county. Each of these infestations has been traced back to livestock feed products contaminated with Palmer seed.

Following the local update, Ohio State University weed scientist Mark Loux spoke. He referred to Preble County as the ‘epicenter of Palmer in Ohio,’ acknowledging that epicenter might not be the appropriate term, but trying to communicate that the infestation here is worse than in other areas. However, he also stated that Preble County has the most organized community effort to eradicate the weed in the state. He talked about the destruction that Palmer can cause, and stated, “I cannot overestimate to you how nasty this weed is. It will cause permanent reductions in your bottom line .”

Following Dr. Loux’s presentation, Stan Wright, agronomist with Crop Production Services, discussed herbicide control options. A major problem in attempting to control the weed is that it is resistant to several herbicide classes. For herbicides that are effective in killing the weed, they should be applied before the weed is 3” tall, which gives a very narrow window for control. Several applications of an effective contact herbicide are required in addition to the use of residual herbicides. Fall burndown herbicide applications are not beneficial for control of this weed.

Preble SWCD wants to emphasize the importance of farmers being able to identify this weed in their fields, and keeping an eye out for it in future years, especially during late summer and fall. It is critical to find infestations early because one or two missed plants during one season can lead to complete crop loss two or three years later.

More information and resources on Palmer amaranth are available at

By Anna Smith

Preble SWCD