Weeds are a persistent challenge for homeowners and gardeners. Understanding different herbicides and their interactions can improve weed management. This article explores two common herbicides, glyphosate and 2,4-D, examining their properties and the considerations for combining them.
Understanding Glyphosate and 2,4-D
Glyphosate, the active ingredient in many non-selective herbicides like Roundup, inhibits an enzyme essential for plant protein synthesis, leading to plant death. As a non-selective systemic herbicide, it controls most annual and perennial plants by absorbing through foliage and translocating to the roots.
In contrast, 2,4-D is a selective systemic herbicide primarily for broadleaf weeds. It mimics natural plant growth hormones, causing uncontrolled cell division and abnormal growth in susceptible plants. This leads to stem curl, leaf withering, and eventual plant death in dicots, while typically leaving grasses unaffected. Many herbicide products contain 2,4-D, often mixed for enhanced control.
The Practice of Tank Mixing
Tank mixing, combining different herbicides in one application, is common for broader weed control. Glyphosate and 2,4-D can be mixed, as they target different weeds with distinct modes of action. However, physical compatibility is not guaranteed; issues like separation or clumping can occur.
A “jar test” is recommended to assess compatibility before mixing a large batch. This involves combining proportionate amounts of each product with water in a small jar. After mixing for 10-15 minutes, check for layering, precipitates, or excessive heat. A successful jar test indicates physical compatibility, but not chemical stability or optimal effectiveness.
Benefits of Combining Herbicides
Combining glyphosate and 2,4-D offers several advantages. This mixture broadens weed control, targeting both grassy and broadleaf weeds simultaneously. Glyphosate controls grasses and many broadleaf species, while 2,4-D enhances control of broadleaf weeds, especially those tolerant to glyphosate alone.
Another benefit is managing herbicide resistance. Applying multiple herbicides with different modes of action reduces selection pressure for resistant biotypes, helping to delay the development of resistant weed populations and maintain effectiveness.
Critical Considerations Before Mixing
Before combining glyphosate and 2,4-D, several important factors warrant careful consideration. Mixing a non-selective herbicide like glyphosate with a selective one like 2,4-D increases the risk of damage to desirable plants, as the resulting mixture will affect both broadleaf and grass species. This means anything sprayed, including turfgrass, could be harmed.
Another concern is the potential for reduced efficacy, known as antagonism, where one herbicide makes the other less effective. Studies have shown that 2,4-D can antagonize glyphosate, particularly in glyphosate-resistant grass weeds, by reducing glyphosate uptake and translocation within the plant. This can lead to poorer control than if glyphosate were applied alone.
Always thoroughly read and follow both product labels, as these are legal documents providing specific instructions, warnings, and compatibility information. Ignoring label directions can lead to unintended consequences, including environmental contamination or increased toxicity.
Guidelines for Safe Application
If choosing to tank mix and apply these herbicides, follow safety guidelines. Always wear personal protective equipment (PPE), including chemical-resistant gloves, eye protection, long-sleeved shirts, long pants, and closed-toe shoes, to minimize exposure.
Use proper mixing procedures, such as the “WALES” method: Wettable powders, Agitation, Liquid flowables, Emulsifiable concentrates, then Surfactants. Accurate sprayer calibration is necessary to ensure the correct amount of herbicide mixture is applied, preventing over- or under-application.
Apply herbicides on calm days, ideally when wind speeds are between 3 and 8 miles per hour, to minimize spray drift. Avoid application near water sources and follow label instructions for proper disposal of leftover mixture and containers to protect the environment.