Project Details:

Title:
Herbicide and Integrated Soybean Weed Management 2019

Parent Project: This is the first year of this project.
Checkoff Organization:Virginia Soybean Board
Categories:Weed control
Organization Project Code:776
Project Year:2019
Lead Principal Investigator:Michael Flessner (Virginia Tech)
Co-Principal Investigators:
Keywords: Cover Crops

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

Objective 1: Cover crops for common ragweed and Palmer amaranth management.
This objective will evaluate common questions about using cover crops for weed suppression:
• Can I just plant wheat or do I need cereal rye?
• Do I need to roll to cover crop or can I leave it standing?
• How much good is the cover crop doing for weed suppression?

The experiment will evaluate combinations of the following: cereal rye versus wheat residue; rolled residue versus left standing; and no, low, medium, or high biomass levels for a total of 13 treatments in 2 locations. Palmer amaranth and common ragweed germination and establishment data will be collected in addition to light penetration, cover crop biomass at termination.

Objectives 2 and 3: Palmer amaranth and common ragweed control with alternatives to glyphosate and ALS herbicides to mitigate PPO resistance-program herbicide approaches and post-emergent herbicide approaches.

Common ragweed and Palmer amaranth survival and seed production will be evaluated from various post-emergent herbicides (objective 2) and herbicide programs (pre-emergent followed by post-emergent (objective 3). These data will be useful to establish research-based recommendations to mitigate PPO resistance and spread thereof into Virginia.

Project Objectives

1) Evaluate wheat and cereal rye cover crops for common ragweed and Palmer amaranth management
2) Assess herbicide-resistant Palmer amaranth and common ragweed control with alternatives to glyphosate and ALS herbicides.
3) Herbicide program approaches for mitigation of PPO resistant common ragweed and Palmer amaranth.

Project Deliverables

All findings will be incorporated into Dr. Flessner’s Extension activities through Virginia Cooperative Extension. It is anticipated that these findings will be disseminated via web-based information, presentations, field day demonstrations, and other media where the information gleaned will be put in the hands of soybean producers. Producers can then implement weed management changes as they see fit. A report to the Virginia Soybean Board will be delievered.

Progress of Work

Final Project Results

Updated August 28, 2020:

View uploaded report PDF file

Results from objective 1 indicate that maximizing cover crop biomass is most important for weed suppression. When sufficient biomass is achieved (~7,500 lbs/ac), similar weed suppression is achieved whether cover crop residues are rolled or left standing. Standing residue is recommended for common ragweed. It resulted in greater control than rolled residue in most cases, despite allowing more light penetration to the soil surface.

Common ragweed and Palmer amaranth survival and seed production were evaluated from various post-emergence herbicides (objective 2) and herbicide programs (pre-emergence followed by post-emergence; objective 3). Palmer amaranth and common ragweed control decreased as size increased for all herbicides. Palmer amaranth control was best and seed production least from glufosinate, dicamba + fomesafen, 2,4-D + fomesafen, and glufosinate + fomesafen. Dicamba, 2,4-D, and glufosinate with or without fomesafen and mesotrione + fomesafen resulted in the greatest biomass reduction.

Farmers should continue to target Palmer amaranth and common ragweed at small sizes (2 to 4 inches in height) for best outcomes. Herbicide program research results reinforce the utility of PPO PREs when used as part of a program with multiple, effective sites of action. Pre-emergence applications of flumioxazin, fomesafen, and sulfentrazone provide effective control and reductions of Palmer amaranth density. Dicamba, 2,4-D, and glufosinate on Palmer amaranth are effective on escapes from PPO-containing PRE herbicides.

Further research is necessary before recommending targeting taller Palmer amaranth and common ragweed for reducing seed production, but results are promising.

Benefit to Soybean Farmers

The information gleaned from this research will be incorporated into Extension activities including web-based information, presentations, and field day demonstrations. Producers may then implement weed management changes or recommendations as they see fit.

Performance Metrics

Project Years

YearProject Title (each year)
2019Herbicide and Integrated Soybean Weed Management 2019