Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED WEED MANAGEMENT SYSTEMS FOR ORGANIC AND CONVENTIONAL CROPS OF THE SOUTHEASTERN COASTAL PLAIN

Location: Crop Protection and Management Research

Title: Severed stems of Amaranthus palmeri are capable of regrowth and seed production in Gossypium hirsuium

Authors
item Sosnoskie, L -
item Webster, Theodore
item Grey, T -
item Culpepper, A -

Submitted to: Annals of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2014
Publication Date: July 1, 2014
Citation: Sosnoskie, L.M., Webster, T.M., Grey, T.L., Culpepper, A.S. 2014. Severed stems of Amaranthus palmeri are capable of regrowth and seed production in Gossypium hirsuium. Annals of Applied Biology. 165(1):147-154.

Interpretive Summary: Palmer amaranth has rapidly become the most troublesome weed species in cotton throughout the southern US, due to the widespread occurrence of glyphosate-resistant populations. Palmer amaranth is an aggressive weed species that can dominate a diversity of agroecosystems, causing significant crop yield losses or even complete crop failure. In the Southeastern United States, there has been resurgence in the use of physical weed control as a means to combat herbicide-resistant Palmer amaranth. Many Georgia growers have resorted to using hand-weeding as a means of eliminating Palmer amaranth that have escaped other control measures. Cotton growers have implemented physical removal of Palmer amaranth from fields in order to facilitate crop harvest and prevent plants from producing seed, which would increase soil seedbank populations. One concern with this physical control tactic is that Palmer amaranth plants that are not completely uprooted or removed from the field can become reestablished. While highly effective, both uprooting and removal are time-consuming and costly strategies. The objective of this study was to describe Palmer amaranth plants regrowth and viable seed production following three levels of incomplete physical control. Field studies were conducted to evaluate the capacity of Palmer amaranth to grow and reproduce following incomplete physical control in cotton fields. Treatments included severing the main stem of flowering plants at heights of 0, 3, and 15 cm above the soil level. Six weeks after treatment, intact Palmer amaranth plants had grown to a mean height of 210 cm and produced 435,000 seeds per plant. Thirty-five percent of the Palmer amaranth plants cut back to a height of 15 cm above the soil level did not recover from the treatment; survivors regrew to a mean height of 97 cm (54% reduction, compared to intact plants) and produced 116,000 seeds per plant (73% reduction). Palmer amaranth plants cut to 3 cm above the soil level had a mortality rate of 64%, an 82% reduction in final plant height, and produced 28,000 seeds per plant. When stems were severed at the soil surface, plant mortality was 95%; final plant height and seed production of survivors were reduced by 95 and 99%, respectively, relative to the control. Therefore, simply severing Palmer amaranth stems as a means of removal, instead of uprooting the entire plant, may allow a significant portion of Palmer amaranth to regrow and produce seed. Subsequent seed production and return to the soil seedbank has multi-season implications for growers. The level of seed production from herbicide resistant A. palmeri plants, intensity of control necessary to prevent seed production, and broad distribution of this weed throughout agronomic fields in the Southern U.S., make seedbank reduction strategies a formidable task.

Technical Abstract: Field studies were conducted to evaluate the capacity of Amaranthus palmeri to grow and reproduce following incomplete physical control in Gossypium hirsutum fields. Amaranthus palmeri plants that emerged simultaneously with a G. hirsutum crop were selected for use. Treatments included severing the main stem of flowering plants at heights of 0, 3, and 15 cm above the soil level. A non-cut/intact control, in which the apical meristem was not removed, was also included. Six weeks after treatment, intact A. palmeri plants had grown to a mean height of 210 cm and produced 435,000 seeds per plant. Thirty-five percent of the A. palmeri plants cut back to a height of 15 cm above the soil level did not recover from the treatment; survivors regrew to a mean height of 97 cm (54% reduction, compared to intact plants) and produced 116,000 seeds per plant (73% reduction). Amaranthus palmeri plants cut to 3 cm above the soil level had a mortality rate of 64%, an 82% reduction in final plant height, and produced 28,000 seeds per plant. When stems were severed at the soil surface, plant mortality was 95%; final plant height and seed production of survivors were reduced by 95 and 99%, respectively, relative to the control. Gossypium hirsutum seeded yields exceeded 3,000 kg ha-1 when A. palmeri plants were cut back to at least 15 cm, whereas yield was reduced 50% in the control treatment, where A. palmeri growth was not interrupted by cutting. In conclusion, while there is immediate benefit of removing A. palmeri plants in terms of G. hirsutum yield, incomplete stem removal can have multi-season implications. Results demonstrate that severely pruned A. palmeri plants can resume growth, reach reproductive maturity and produce viable seed, which have the potential to repopulate soil seedbanks

Last Modified: 10/25/2014
Footer Content Back to Top of Page