Researchers Collecting Resistant Weeds

Researchers from Ohio State University's College of Food, Agricultural, and Environmental Sciences are collecting samples of several weed varieties that are herbicide-resistant and could pose problems for growers in the region.

Published on: Oct 8, 2013

Mark Loux, OSU Extension weed specialist, is tracking herbicide-resistant weeds that are beginning to show up in Ohio fields that have caused problems for growers in other states. The goal is to try to prevent the weeds' further spread in Ohio.

 At the top of the wanted list is Palmer amaranth, which is also known to many cotton and soybean farmers in the South as a "pigweed on steroids." Palmer amaranth, which is a glyphosate-resistant weed that has wreaked havoc for Southern U.S. growers, has now been found at several sites in Ohio.

"We are ideally looking for seeds from plants that survived a herbicide program that has typically provided effective control in the past, or repeated application of glyphosate or other herbicides," Loux says.

WICKED WEED: Palmer amaranth has been foun din several Ohio locations and is at the top of the lsit for resistant pests.
WICKED WEED: Palmer amaranth has been foun din several Ohio locations and is at the top of the lsit for resistant pests.

Other weeds from crop fields the team is looking for include seeds from populations of johnsongrass, and pigweeds, such as redroot pigweed, waterhemp and Powell amaranth.

A benefit of tracking these weeds is that the data can be used to see where the problems are and try to stay ahead of problems that are developing.

"We can also use the data to raise awareness of the next problems growers could be facing," loux says. "Palmer amaranth is a huge problem in the south and we want to let people know that it has been found here in Ohio.

"Waterhemp is increasing and spreading through the state as well. And we've gotten some reports from growers that johnsongrass, which has previously been reasonably controlled, this year has become a problem for some Ohio growers."

In addition to raising awareness, the researchers can use the data to develop management and control recommendations for Ohio growers.

Signs that a resistance problem might be developing include patches of surviving weeds in a field that is otherwise free of weeds or an atypical appearance of plants due to regrowth following treatment with herbicide.

The weed samples will be accepted until Oct. 30, with a goal of emailing results to growers in February or March.

The sample submission form can be found at

Guidelines for sample submission:

* Samples should be collected when the seed is mature.

* The sample should be fresh.

* The sample should be collected and stored in paper, not plastic, bags.

* The samples should be stored in open paper bags in cool, dry conditions until mailed.

* Samples should be carefully packaged and shipped early in the week to avoid weekend layovers during which the sample will deteriorate.

* Be sure to include sample documentation and background information.

Samples can be sent to: Mark Loux, Horticulture and Crop Science, 2021 Coffey Road, Columbus, Ohio 43210.