What Are the Best Herbicide Programs for Identity Preserved (IP) Soybeans?

Ontario field studies have ranked herbicide treatments based on how well weeds were controlled and relative soybean yields. Over the past two years, the winner has been the low rate of Boundary applied pre-emergent followed by Reflex + Pinnacle + Assure II applied post-emergent. A number of one-pass pre-emergent treatments have been a close second. Below is a summary of the last two field seasons.

Table 1. Top 8 weed management programs for identity preserved soybeans based on overall weed control and yield.
Weed Control Efficacy (%)
Rank*
Treatment
Grass
Broadleaf
Yield Index
1
"Two-Pass" System
Boundary (PRE - low rate)
Reflex + Pinnacle + Assure II (POST)
99
90
0.98
2
Conquest + Valtera (PRE - low rate)
99
95
0.96
3
Broadstrike Dual Magnum (PRE)
97
83
0.95
4
Conquest (PRE - low rate)
94
81
0.92
5
Boundary (PRE - low rate)
98
86
0.90
6
Pursuit + Valtera (PRE - high rate)
95
85
0.90
7
Pursuit (PRE - high rate)
81
68
0.89
8
Cleansweep (POST)
92
80
0.85

Rank based on weed efficacy and soybean yield with a greater weight placed on relative soybean yield. Cost of the treatment is not factored into the overall rank.

Uncontrolled weed species (<80% control) by herbicide:

  • Barnyard grass: Pursuit (PRE - high rate)
  • Lamb's-quarters (triazine resistant): Boundary (PRE - low rate)
  • Pigweed species (group 2 resistant): Pursuit (PRE - high rate)
  • Ragweed: Boundary (low rate), Conquest (low rate), Pursuit, Pursuit + Valtera

Tufted Vetch Activity:

Conquest + Valtera gave the best tufted vetch suppression of all treatments tested in 2010.

Acknowledgements: This project is funded by the Grain Farmers of Ontario


For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047
E-mail: ag.info.omafra@ontario.ca
Author: Mike Cowbrough - Weed Specialist/OMAFRA; François Tardif and Clarence Swanton/University of Guelph
Creation Date: 12 March 2010
Last Reviewed: 12 March 2010