New and Promising Weed Control Technologies
Management/control of weeds in Midsouth soybeans is arguably the most impactful and expensive issue affecting soybean producers. And with the advent of herbicide resistance [HR] in many problematic weed species, control options are dwindling for those species. Thus, it is necessary to be aware of and explore other control measures that may be effective in lieu of herbicides. The following narrative addresses promising alternative weed control methods that may fill this need.
Targeted Spraying/Smart Sprayer
This technology uses cameras mounted on the sprayer to detect weeds so that nozzles can be turned on automatically to spray them with an efficacious herbicide. The intent of smart spraying technology is to optimize spraying results by using sensors, data, and variable rate systems to enhance efficiency and reduce the environmental impact of chemical applications. The advantage of this technology is realized from 1) targeting only emerged weeds for postemergence [POST] applications [no spraying of non-infested field areas], 2) reducing herbicide use and subsequent costs, 3) reducing herbicide deposition and runoff, 4) reducing off-target exposure potential, and 5) having less crop injury/reduced crop stress resulting from a foliar herbicide application to non-GMO soybeans where only small areas that have weeds present are sprayed.
These systems will work best in fields that have low weed pressure as a result of effective preemergence [PRE] herbicide applicatons. The equipment likely will be expensive and include annual subscription fees. The greatest value from using this technology will be accrued by custom applicators who capture value in their per-acre fee structure, or producers who farm a very large acreage. This technology will likely not be used as part of a total POST program for weed control in soybeans since weed densities will normally be too high for the “spot” spraying that is an integral part of the system. Thus, it is more likely to be used to spray weeds that have escaped where a PRE herbicide program was used.
And finally, the technology can:
• Be more cost-effective where multiple POST applications must be made to a crop;
• Be used where a targeted spray option makes controlling sporadic weed infestations more cost-effective;
• Result in less chemical going into the ground so that present and future regulations dictating lower chemical use in agriculture can be met;
• Be retrofitted to an existing sprayer to lower initial cost;
• Improve the return on investment when multiple pesticides [e.g. fungicide and herbicide] can be applied simultaneously;
• Result in POST herbicides that were too expensive to develop and market for broadcast applications being developed and marketed for “spot” or targeted application.
An article titled “Smart spraying technologies for precision weed management: A review” reviews the different methods used in precision weed management, machine vision techniques, and weed spraying systems. A final conclusion by the authors that “More work needs to be done to conduct actual field trials on raised beds and crop rows with the weed management systems to better gage the adaptability of these systems to real-life conditions” certainly indicates the infancy of this technology and how it can be used most effectively in crop production once perfected. Research is presently being conducted in this area, and hopefully will yield results that can be applied to make this technology a cost-effective, every-season reality for weed control.
An article titled “Smart Spraying Technology in Agriculture” provides a concise presentation of the following subjects:
• What is Smart Spraying?
• Key Components of Smart Spraying Systems;
• Major Applications of Smart Spraying;
• Benefits of Smart Spraying Technology in Agriculture;
• Challenges for Adoption of Smart Spraying Technology;
• Conclusion that contains the statement “smart spraying technology in agriculture offers a crucial opportunity to transform agriculture spraying into a more efficient, targeted, and environmentally responsible activity”.
Electrocution of Weeds
• Weed management by electrocution is basically a “rescue” control strategy since weeds targeted for control are large and extend above the crop canopy.
• The objective when using an electrocution tool is to control large plants that have escaped previous control measures, and reduce the production of viable weed seeds by those plants.
• Weed control by electrocution is ideal for use in fields that have scattered weeds that have grown to a height that is above the crop canopy.
• Accidental contact by the electrocution apparatus with the crop may result in crop injury that will reduce yield.
An article by Schreier, Bish, and Bradley titled “The impact of electrocution treatments on weed control and weed seed viability in soybean” provides the following results from field experiments that were conducted in 2020-21 near Columbia, Missouri.
• Two passes vs. one by the electrocution apparatus gave a greater level of weed control in some cases.
• Overall, there was a trend toward greater weed control when electrocution occurred at later growth stages of the weeds.
• Generally, broadleaf vs. grass weeds were controlled better by the electrocution process.
• Control of all weed species in the study was related to weed height and amount of moisture in the weed plants. Taller weed plants were controlled better, and weed plants with greater plant moisture were controlled less.
• Finally, electrocution of weeds as part of an integrated management program could eliminate late-season HR weed escapes, and reduce the number of viable seed that would have been produced by those weed plants. Thus, weed electrocution should be viewed as a late-season “rescue” treatment that can rid a field of escaped HR weeds and reduce the number of viable seed that are returned to the soil.
Weed Control at Harvest
Dr. Jon Jackson of Global Neighbor Inc. has developed the Directed Energy Unit that uses a combination of blue light and heat to destroy seed of several weed species. According to information on the GROW website, researchers at Texas A&M University are evaluating the effectiveness of the device that is touted to kill as much as 83% of Palmer amaranth weed seeds. They are also exploring ways to integrate the unit into a combine so that the targeted weed seeds are exposed to the combination of blue light and heat as they pass through the combine. This device, if effective, would then become another method to consider for Harvest Weed Seed Control [HWSC].
Final Thoughts
Some of these technologies may seem far-fetched now, but as more weeds become resistant to herbicides, more consideration must be given to these alternative weed control measures. After all, it is likely that alternatives to chemical weed control will be needed in the future to control HR weeds so that producers can remove them and their yield-robbing effect.
Composed by Larry G. Heatherly, July 2024, larryh91746@gmail.com