March 20, 2023
Trial Objective
Determine if XtendiMax® herbicide with VaporGrip® Technology*, a restricted use pesticide, provides a broadacre benefit of residual weed control when used in conjunction with pre-emergence (PRE) residual herbicides in a conventionally tilled soybean system.
Research Site Details
- There were 34 research locations with 11 sites in 2021 and 23 in 2022. The locations represented 17 states (AR, IA, IL, KS, LA, MI, MN, MO, MS, ND, NE, OH, OK, SD, TN, TX, and WI).
- The protocol included conventional tillage prior to planting to remove existing weeds.
- Pre-emergence (PRE) products were applied at either planting or prior to soybean emergence.
- There were no post-emergence (POST) applications made in order to determine the effectiveness and duration of residual weed control.
- Weed control was evaluated 35 days after treatment (DAT).
- Generalized Linear Mixed model with Replicated Measures was used to generate LS Means using α = 0.05.
- Weather service from The Weather Company, an IBM Business, was used to model precipitation for each site by using latitude and longitude coordinates.
*XtendiMax® herbicide with VaporGrip® Technology is a restricted use pesticide and must be used with VaporGrip® Xtra Agent (or an equivalent volatility reduction adjuvant). For approved tank-mix products (including VRAs and DRAs), nozzles and other important label information visit XtendiMaxApplicationRequirements.com. Applicators must check XtendiMaxApplicationRequirements.com no more than 7 days before application of this product for additional labeling, including state restrictions. Where applicable, users must comply with additional requirements found on this website.
Table 1. Herbicide treatments applied either at planting or prior to soybean emergence.
Understanding the Results
- With two years of data at 29 locations (out of the 34 locations, 29 provided usable data at the 35 days after treatment rating timing), the average percent control of broadleaf weeds, 35 days after treatment (DAT), ranged from 62 to 76.9% for the pre-emergence products only and 82.9 to 88.6% control for pre-emergence products with the addition of XtendiMax® herbicide with VaporGrip® Technology*, a restricted use pesticide (Figure 1).
- With two years of data at 18 locations (out of the 34 locations, 18 provided usable data at the 35 days after treatment rating timing), the percent control of large-seeded broadleaf weeds, 35 days after treatment (DAT), ranged from 55.7 to 77.9% for the pre-emergence products only and 85.5 to 90.4% control for pre-emergence products with the addition of XtendiMax herbicide (Figure 2).
- With two years of data at 25 locations, the average percent control of Amaranthus species, 35 days after treatment (DAT), ranged from 66.9 to 82.1% for the pre-emergence products only and 78.8 to 88.7% control for pre-emergence products with the addition of XtendiMax herbicide (Figure 3). Fierce® EZ herbicide, Valor® EZ herbicide, and Authority® MTZ herbicide were improved with the addition of XtendiMax herbicide (Figure 3).
- Residual herbicides generally perform better if rainfall occurs shortly after application. When less than 0.5 inches of rain occurred within one week of application, the average percent control of broadleaf weeds with pre-emergence products alone only ranged from 56.4 to 73.2% while control ranging from 82.7 to 90.8% was observed for pre-emergence products with the addition of XtendiMax herbicide (Figures 4, 6, and 7).
- When greater than 0.5 inches of rain occurred within one week of application, the average percent control of broadleaf weeds with pre-emergence products alone ranged from 66.5 to 80.8% and 83 to 88% for pre-emergence products with the addition of XtendiMax® herbicide with VaporGrip® Technology
*, a restricted use pesticide (Figures 5, 6, and 7).
Figure 1. Average percent control of pre-emergence products alone and with XtendiMax® herbicide with VaporGrip® Technology, a restricted use pesticide, at 8 locations 21 days after application. (Averages followed by same letter are not significantly different using Fishers Protected LSD at < 0.05).
Figure 2. Average percent control of large-seeded broadleaf weeds with pre-emerge products alone and paired with XtendiMax® herbicide with VaporGrip® Technology*, a restricted use pesticide, at 9 locations 35 days after application for the years 2021-2022. (Averages followed by same letter are not significantly different using Fishers Protected LSD at ρ < 0.05).
Figure 3. Average percent control of Amaranthus (pigweed) species with pre-emerge products alone and paired with XtendiMax® herbicide with VaporGrip® Technology*, a restricted use pesticide, at 25 locations, 35 days after application for the years 2021-2022. (Averages followed by same letter are not significantly different using Fishers Protected LSD at ρ < 0.05).
Figure 4. Average percent control of broadleaf weed species with pre-emerge products alone and paired with XtendiMax® herbicide with VaporGrip® Technology*, a restricted use pesticide, at 6 locations, 35 days after application when < 0.5 inches of rainfall occurred one week after treatment application. (Averages followed by same letter are not significantly different using Fishers Protected LSD at ρ < 0.05).
Figure 6. Comparison of average percent control of broadleaf weed species 35 days after application between locations that received less than or greater than 0.5 inches of rainfall. There were 23 locations in 2021-2022 with greater than 0.5 inches of rain and 6 locations in 2021-2022 with less than 0.5 inches of rain.
Figure 8. Comparison of broadleaf weed control at Rosemount, MN. Applications made 5/26/22 and photos were taken 20 days later on 6/15/22. A: Untreated Control; B: Valor® EZ herbicide alone; C: Valor® EZ herbicide paired with XtendiMax® herbicide with VaporGrip® Technology*, a restricted use pesticide.
Figure 9. Comparison of broadleaf weed control at Carbondale, IL. A: Warrant® herbicide alone; B: Warrant® herbicide paired with XtendiMax® herbicide with VaporGrip® Technology*, a restricted use pesticide. Pictures used with the permission of Eric Miller, Southern Illinois University, Carbondale, IL.
Key Learnings
- Two years of analysis shows that the addition of XtendiMax® herbicide with VaporGrip® Technology, a restricted use pesticide, to traditional residual herbicides at-planting improves residual broadleaf weed control up to 35 days after application.
- This holds true when looking at residual control of large-seeded broadleaf weeds, exclusively.
- Residual control of problematic Amaranthus species was improved 35 DAT when XtendiMax® herbicide was added to acetochlor, Fierce® EZ herbicide, Valor® EZ herbicide, and Authority® MTZ herbicide.
- Level of residual weed control appears to remain consistent when XtendiMax® herbicide with VaporGrip® Technology, a restricted use pesticide, is added even with minimal rainfall within the first week after application.
- Using XtendiMax® herbicide in the PRE/at-plant application with other residual herbicides adds confidence for weed control.
- Getting XtendiMax® herbicide on the acre, even PRE, helps with season-long weed control.
- Reduces selection pressure for herbicide resistance development on the post-emergence application.
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