Sorghum field

Herbicide programs for sorghum

April 24, 2023 1:00 p.m.


Sorghum is a sustainable cropping solution for a wide range of geographies. It is a resilient crop with natural drought and heat tolerance that allows for profitable production in a variety of conditions and the ability to rapidly respond to increased resources. Furthermore, market development has contributed to an increased global demand for sorghum. One of the challenges of sorghum production has been the lack of effective weed control options, particularly for grass weeds. This challenge was recently addressed by Advanta Seeds, who provided the first commercially available herbicide tolerant sorghum to the United States in 2021. Known as igrowth®, this herbicide tolerant sorghum is available in both grain and forage hybrids and is tolerant to IMIFLEX Herbicide offered by UPL. Much like any system, there are important aspects that growers and advisers should consider to optimize the success of this technology, which will allow growers to realize the full potential of their sorghum acres.

  1. igrowth Sorghum Overview

    1. igrowth was developed and commercialized by Advanta Seeds. This technology experienced a full commercial launch in the United States in 2021, with many several of successful international use in Argentina, Uruguay, and Australia prior to this.
    2. igrowth is a Non-GMO trait, developed through mutagenesis in sorghum. Since igrowth was developed in sorghum, there were no undesirable agronomic characteristics that plant breeders needed to remove from the hybrids. Furthermore, the non-GMO status leads to no channeling or export restrictions of igrowth sorghum grain.
    3. igrowth is a homozygous-recessive trait – what this means is that both parents must possess the igrowth gene. This feature provides multiple benefits, which include excellent crop safety from this 2 gene system, in addition to the ability for production fields of igrowth sorghum to be sprayed with IMIFLEX. These applications allow for off-types (plants that do not contain the igrowth trait) to be chemically controlled before they produce seed. These features lead to industry leading crop safety of the igrowth system and excellent trait purity in the bag.
    4. igrowth is available in both grain and forage sorghum hybrids that fit a variety of production goals and environments.
    5. Stewardship of igrowth and IMIFLEX is of the utmost importance to Advanta, UPL, and their partners. Growers and advisers should always follow the established stewardship guidelines to preserve the benefits and flexibility this technology now provides sorghum growers. Go to AgCelerate to obtain a license number to purchase and plant igrowth seed.
  2. IMIFLEX Herbicide Basics with igrowth Sorghum

    1. The active ingredient in IMIFLEX Herbicide is imazamox, a Group 2 herbicide. IMIFLEX features both post-emergent and pre-emergent activity on a long list of grass and broadleaf weeds. Key weeds species include Texas panicum, crabgrass, signalgrass, foxtail species, field sandbur and a range of broadleaf weeds. IMIFLEX should only be applied to igrowth sorghum as it will kill non-igrowth hybrids.
    2. Traditionally, imazamox has only been used as a post-emergent product. However, a unique innovation with IMIFLEX is that it is labelled for either pre-emergent or post-emergent applications to igrowth sorghum. This allows growers the flexibility to identify where IMIFLEX fits best in their standard herbicide programs. Increased efficacy has been observed on key weeds like Texas panicum from pre-emergent applications of IMIFLEX. Post-emergent applications are optimized by targeting small, actively growing weeds that are less than 2-3” in height.
    3. For pre-emergent applications, IMIFLEX can be applied to igrowth sorghum at 6 – 9 fl oz/A, post-emergent applications are a single 6 fl oz/A rate. Growers are limited to one application of IMIFLEX to igrowth sorghum/year. Crop safety of IMIFLEX applications to igrowth sorghum is excellent across application timings and rates. Research trials across the sorghum belt have continued to document very little, if any crop response as a result of an IMIFLEX application to igrowth sorghum.
    4. IMIFLEX has a wide application window with igrowth sorghum and can be applied anywhere from pre-emergence up to 20” in crop height. There is no minimum crop height restriction for post-emergent applications of IMIFLEX to igrowth sorghum, which allows growers to apply this product when it is most effective on the weeds and not have to worry about safety to the crop.
    5. Flexible rotational intervals make IMIFLEX and igrowth sorghum a tool that can be implemented in a variety of crop rotation scenarios. Plant-back intervals allow for cotton, corn, wheat, soybeans, and variety of other crops to be rotated to the following cropping season.
    6. Pre-emergence applications of IMIFLEX should be applied before or shortly after planting, and receive rainfall or overhead irrigation for activation. Post-emergent applications should be made ~28 days after the pre-emergent program is applied or when weeds reach 2-3” in height, whichever comes first.
    7. Tank-mixing is an important aspect for all herbicide programs and IMIFLEX is incredibly flexible when it comes to tank-mixtures with other sorghum herbicides. The only products IMIFLEX cannot be tank-mixed with are Huskie®, Peak®, and Ally®. Due to flexible tank-mixing, IMIFLEX can be readily mixed with broadleaf material like 2,4-D, fluroxypyr, and dicamba.
    8. Use NIS, COC, or MSO in combination with a nitrogen source (either AMS or UAN) with post-emergent applications of IMIFLEX. Rates of COC or MSO should be 1 – 2% v/v, while NIS is 0.25% v/v, AMS should be used at 12 – 20 lbs/100 gallons of water and UAN at 2.5 – 5.0% v/v. Utilize higher ends of the respective rate ranges an more aggressive adjuvant combinations (MSO + UAN) when weeds are experiencing stress. Do not use an oil-based adjuvant when tank-mixing with 2,4-D or dicamba, use NIS instead. Apply IMIFLEX in at least 15 gallons of water/acre.
  3. Program Approach for Optimized Weed Control

    1. IMIFLEX is a flexible option that will compliment existing herbicide programs very well. Whether IMIFLEX is use pre- or post-emergence, a group 15 herbicide should be included in that herbicide program for optimized performance and resistance management. S-metolachlor formulations like MOCCASIN® or MOCCASIN II Plus perform very well when used in combination or preceding an IMIFLEX application. When added activity on pigweeds is needed, especially ALS-resistant pigweeds, incorporating a mesotrione containing product like MOTIF® or a premix of s-metolachlor + mesotrione like COYOTE® can optimize performance. Mesotrione containing products are labelled for up to 21-day preplant and pre-emergence applications to grain sorghum. Applications made within 7 days of planting can increase the risk of crop response.
    2. UPL’s recommendation for herbicide programs with IMIFLEX and igrowth sorghum are as follows:

      UPL data table