Problems with Iron Based Weed Control

Example of Iron Leaching on River Estuary

Iron-based herbicides are now being sold as a one size fits all spray for all types of broadleaves. Iron-based weed control has even been proposed as a more natural alternative to chemical herbicides, which are known to have negative impacts on the environment and human health. But, the use of iron-based herbicides for weed control also has significant drawbacks, and in this blog post we will argue that their use should be carefully considered, minimized and even eliminated altogether in your garden routine. It is always best to attack the root cause of the problems (THE SOIL!). 

The first major problem with iron-based herbicides is their potential negative impact on soil microbiology. Iron is an essential nutrient for plants, but excessive amounts of iron can be toxic to soil microorganisms, which play a critical role in maintaining soil health and fertility. These microorganisms break down organic matter and cycle nutrients, including iron, to plants. The use of iron-based herbicides can lead to the accumulation of iron in the soil, which can inhibit the growth of beneficial microorganisms and disrupt nutrient cycling processes. This can have long-term impacts on soil health and plant productivity, and may require additional inputs of fertilizers and soil amendments to mitigate.

In addition to their impacts on soil microbiology, and this is point number 2, iron-based herbicides can also have negative effects on aquatic ecosystems. When iron is applied, it can leach into nearby waterways, where it can be toxic to fish and other aquatic organisms. This can have significant ecological impacts, especially in areas where water quality is already compromised due to other stressors. Iron-based herbicides may also contribute to the formation of harmful algal blooms, which can further degrade water quality and harm aquatic life. In Austin, we have unfortunately had experienced this. Rivers that used to be deemed safe for dogs to swim are now off limits due to the risk of blue-green algal blooms. In fact, Austinites are now being warned to assume that all algal blooms harmful and to simply avoid it altogether.

Third, iron-based herbicides are not always effective against all types of weeds. Some species may be resistant to iron-based herbicides, and multiple applications may be necessary to achieve adequate control. This can lead to increased costs, as well as elevated environmental risks and exposure associated with repeated applications. On top of this, iron-based herbicides can damage or kill desirable plants if not applied carefully or in the right conditions. This can have significant economic impacts especially those growing sensitive crops in their backyards. There is a reason why iron-based herbicides for weed control is highly regulated. There is a reason why the spray bottle has the word, "CAUTION", on its label. 

Fourth, while the initial cost of iron-based herbicides may be lower than chemical herbicides, the need for multiple applications and potential impacts on soil health may increase overall costs in the long run. Iron-based herbicides can be more expensive and less effective than just manually removing weeds by hand and maintaining soil health. This means that if broadleaves are all over your lawn, you have a soil problem, not an iron problem. 

Fifth issue with iron-based herbicides is their potential to contribute to the development of herbicide-resistant weeds. While iron-based herbicides are not currently used as widely as chemical herbicides, the repeated use of any herbicide can naturally select - through the Theory of Natural Selection, thank you very much Charles Darwin - for weed populations that are resistant to its mode of action. This can lead to the development of superweeds that are difficult or impossible to control, and may require even more toxic or expensive herbicides to manage. The potential for herbicide-resistant weeds is a significant concern, and the use of iron-based herbicides may exacerbate this problem.

To conclude, while iron-based herbicides may offer some benefits as an alternative to chemical herbicides, their use should be carefully considered, minimized, and even eliminated whenever possible. The potential negative impacts on soil microbiology and aquatic ecosystems, as well as their limited effectiveness against some weed species, high costs, and potential to contribute to herbicide resistance, all highlight the need for caution when using these products. Homeowners should explore a range of weed control methods, including cultural and biological controls, ground covers, overseeding, checking for soil pH, availability of nutrients, core aeration, as well as manual removal, to develop a holistically integrated organic weed management strategies that are sustainable, cost-effective, and environmentally responsible.

But then again, who are we? We may have a conflict of interest against iron-based herbicide manufacturers. That is why we are leaving the International Rice Research Institute (IRRI) to give the final word about iron toxicity in soil, "There is currently no practical field management option to treat iron toxicity."