Avoid herbicide misuse at home, things to know before you buy
A little herbicide homework can increase efficacy, safety and cost savings.
The Environmental Protection Agency (EPA) estimates that 88 million U.S. households use pesticides, according to the EPA Pesticide Industry Sales and Usage 2017. The largest class of pesticide used is insecticides (indoors and outdoors), followed herbicides (about 52 million households) and fungicides. Unlike agricultural applications, no training or certification is required to buy pesticides for residential use. This opens the door to potential misuse, unintentional or otherwise.
The label that comes with the pesticides you buy at the store is a legal document. It has been vetted and approved by the EPA and is based on several required research studies during the registration process (read more at EPA: About Pesticide Registration). Not following the labeled directions is an illegal action. Misuse can happen as the result of using the wrong product (ineffective for the target pest), applying the wrong amount, inappropriate sites or weather conditions, etc.
The pesticide aisle at your local store can be intimidating; what appears to be hundreds of different products in flashy bottles can be overwhelming (Photo 1). One of the keys to successfully using all pesticides is to do some homework before you go to the store. Here are some special considerations regarding herbicides.
Know the identity of your enemy (i.e., plant pest)
Only by knowing what you are up against can you make the best choice in product and active ingredient(s). If you are unsure of the plant’s true identity, consult local experts. Michigan State University Extension offices and MSU Plant & Pest Diagnostics handle these types of questions on an daily basis. Another option would be to test out a smartphone app. Just bear in mind that apps can inadvertently lead you astray, so double check your findings with a trusted resource.
Consider your location and any possible hazards
Herbicides do not always stay where you apply them. They can move at the time of application (e.g., drift or volatilization) or afterward (e.g., precipitation/irrigation events) and some can persist or leach, causing unexpected results later in time. Think about the risks to unintended plants and other organisms.
While integrated weed management is always a good idea (i.e., combination of cultural, physical and chemical controls), if this is a sensitive area, more focus should be on cultural and physical control options before resorting to an herbicide. For example, herbicide applications on the edge of waterways require special consideration. Most readily available products are not labeled for aquatic use and could have negative consequences for those environments and wildlife. Remember, the label is the law. If the application area is along the St. Clair River, one of the Great Lakes, or is being made to the water, a permit is required by the Michigan Department of Environment, Great Lakes, and Energy (EGLE), and hiring a certified professional should be considered.
Choose a product ahead of time
Now that you know what your weed is and have thought through the area, it is time to choose an effective product. All herbicides contain an active ingredient (or more than one) that kills plants and inert ingredients that make the product easy to handle. Many of the large herbicide producers have residential use websites to help guide you to the best product. There are also third party sites that can help like DoMyOwn.com. While MSU does not endorse any particular site, these are a good starting point as the website owners have a vested interest in your success with their products.
Once you have found one or more herbicides that would work, review the label to make sure it is appropriate for your treatment area. Then, write down the active ingredient(s) listed and the percentage. It is almost always the tiniest print on the label (Figure 2)!
Be sure that the product you choose is intended for the area you intend to treat. For instance, you would not want to apply lawn herbicides in a vegetable or ornamental bed. Not only could these products harm the desired plants, but they may leave hazardous residues on produce or persist. When the EPA approves labels, it is only for the habitat or crop listed.
Decide if you prefer a ready to use formula or a concentrate
Some herbicides come in both a ready-to-use form and a concentrate. If you do not have a dedicated pump or backpack type sprayer for applying herbicides and/or do not wish to measure out and mix the chemicals with water, the ready-to-use products will ease your application process.
Plan to protect yourself and the environment
Labels are required to list all personal protective equipment (PPE) at the time of application. This does not prohibit you from wearing additional PPE. Examples of PPE that are good to consider are waterproof boots or shoes, long pants and shirts, waterproof gloves and eye protection. If you are working with a dry, granular product, a dust mask may also be appropriate or desired. After the application, people and pets may need to stay out of the treated area until dry or for a particular amount of time. Again, refer to the label for exact details on required PPE and notes on the reentry.
Protecting the environment can relate back to the sensitive areas already discussed (Figure 2), but it can also relate to conditions at the time of application and the amount applied. Usually, the weather conditions of most concern are listed on the label. As an example, when applying liquid herbicides with 2,4-D or dicamba to control broadleaf weeds, it will often state that applications cannot be made when air temperatures are at or above 85 degrees Fahrenheit. This is to prevent volatilization. Other conditions to consider that might not be listed and can affect efficacy and/or movement in the environment include air temperature (too cold or hot) and humidity, water stress (again, too little or too much), and windy conditions (observe tree leaf movement or flags in the area as a good visual and be aware of gusts).
Over applying herbicides will not necessarily kill them faster and can lead to unwanted movement or persistence. Follow the labeled recommendations.
Do not expect instant gratification
Did you know that pelargonic acid has been added to several glyphosate products not because it helps control the weeds any better but because it shows the product is working sooner? Glyphosate alone is very effective at killing most plants, but it can take up to two weeks to see full activity. With that in mind, be patient before deciding to apply more herbicide.
Once you get to the store, check to make sure the product you are buying has the active ingredient(s) you intended. Companies can sometimes keep a trade name and change the chemical composition without it being obvious. Again, the active ingredients are often the smallest print on the label, so don’t forget to bring your glasses.
Do not rely on help at the store. While store employees have the best intentions, they do not always have training in specific areas of pest control. There have been numerous cases in the diagnostic lab that start with, “Well, the people at the store told me….” that did not end with the expected result.
If in doubt, reach out to the previously mentioned resources. That is what we are here for!