~ There is no “Swiss Army Knife” of herbicides, you must match the tool (the chemistry) to the task (the weed) – “the right tool for the job” ~
April 7, 2022 – As our minds turn to gardening and hopes of warmer weather, we might think about weed control. There are many choices of herbicides at the store – but which one is right for your weed problem? The April 7th 2022 Sustainable, Secure Food Blog explains that while there is no one-size fits all solution, there are ways to chose the right solution for the right problem.
Photo: Thistles are another common weed in home gardens. Dithiopyr (Dimension) is a selective, pre-emergent chemistry. One potential gotcha: this herbicide can only be used by commercial applicators in New York State. This highlights the need to always refer to the label! Credit: Canva Pro
According to blogger Timothy Durham, hand pulling weeds can be a prudent solution. This is especially true if your weeds are few and far between. “But herbicides can be a gamechanger, if you ‘use the right tool for the job.’ Herbicides are designed to chemically manage weeds: devious, out of place plants that sabotage our fragile green thumbs.”
Unfortunately, there is no “Swiss Army Knife” of herbicides. They’re as diverse as a mechanic’s toolkit. Avoid the temptation to pluck anything from the shelf and apply it indiscriminately. Selection must be intentional – a careful alignment of herbicide properties with the weed(s) in question.
Fortunately, herbicides are grouped in straightforward ways, often in very black and white pairings. It’s important to understand how these branch points guide the decision-making process, so an appropriate choice can be made.
Pre-emergent herbicides are a pre-emptive strike. When applied and watered into the soil, they create an inhibitory chemical barrier around ungerminated weed seeds, preventing sprouting. Established plants are spared because most of their roots lie outside this shallow barricade.
Obviously, pre-emergent herbicides must be applied in anticipation of a problem. It’s also a solid option for newly prepared beds. If weeds are already growing, you’ve missed the window of opportunity. As an alternative to pre-emergent herbicides, consider growing cover crops in your garden, yet another valuable tool to keep weeds at bay.
Post-emergent herbicides are reactive, requiring a newly germinated (or established) weed.
Another comparison of herbicides is to look at Selective (Narrow Spectrum) vs. Non-Selective (Broad Spectrum). This pairing is a subset of the above. Does the situation call for a delicate surgeon’s scalpel (that only targets certain weeds), or a blunt force clubbing (an indiscriminate herbicide)? If you’re looking to perform a “reboot” in the garden and start from scratch, broad-spectrum herbicides are your best bet. Otherwise, you’re probably in the market for some selectivity based on the weeds present.
Another consideration is the often-misunderstood Mode of Action. This is what the herbicide ultimately does to the weed.
Various modes of action include:
- Lipid biosynthesis inhibitors – prevents lipid (fat) production essential for cell membranes
- Amino acid biosynthesis inhibitors – prevents amino acid production (building blocks of proteins)
- Plant growth regulators – hormone disruption, causes the plant to grow itself to death
- Photosynthesis inhibitors – backlogs photosynthesis, causes reactive species to accumulate that poison/disrupt cell integrity
- Nitrogen metabolism inhibitors – disrupts cell functions, shuts down photosynthesis
- Pigment synthesis inhibitors – destroys chlorophyll, which is necessary to harvest light in photosynthesis
- Cell membrane disruptors – causes cells to “leak” and disintegrate
- Seedling growth inhibitors – inhibits cell division, root extension and growth
This is a vital consideration due to the threat of resistance. Repeatedly spraying the same herbicide against the same weeds leads to resistant populations. To effectively manage, it’s important to switch things up with herbicides that work with diverse modes of action. This keeps weeds off balance and unable to adapt (or at least stifles them a bit).
To read the entire blog, visit: https://sustainable-secure-food-blog.com/2022/04/07/get-out-of-the-weeds-use-the-right-tool-for-the-job