Proper control of weeds, insects and diseases is an important and necessary component of any turfgrass management system. On athletic fields, this is not only for the purpose of aesthetics, but also from the standpoint of ensuring that the turfgrass system provides proper traction and footing. Most likely, it should reduce the possibility of injury to the users of the field.
Depending on which pest you consider, pesticides are either a tool that can be used to make the management of turfgrass pests easier (i.e., dandelions and other tap-rooted weeds), or perhaps they are the only plausible way of dealing with a particular pest (i.e., grey leaf spot or another pathogen).
The use of pesticides became widespread on turfgrass systems in the 1960s and 1970s. The controversy associated with their use soon followed. Because of this, there are various laws that govern whether and what pesticides you may use. Depending on where you are, you may be free to use legally registered pesticides, the list of products may be restricted or you may not be allowed to apply anything for the control of pests on the turf. In many cases in those areas where you are legally permitted to apply pesticides, you may have been faced with speaking with concerned citizens/users of the fields about the types of products you are applying and any risks associated with their use.
Pesticide use continues to be a hot-button issue. Thus, there will be people who a) don’t care, b) think all pesticides are bad no matter what you say, or c) have some concerns about whether the use of pesticides on your fields is appropriate and responsible.
This month’s article attempts to address some of the more commonly encountered questions I have heard over the years about pesticides.
Q: What are you spraying?
You are legally required to be able to answer this question. You must also have the label and safety data sheet (SDS) available for inspection.
Given the debates around pesticide use, it’s perfectly normal to hear this question.
If someone approaches you while making the application, direct him or her off of the field before speaking with them. I find that this happens more often when an application is being made that’s a granular formulation.
I also find that it’s a good idea to be able to explain in layman’s terms what the active ingredients are in the product and the specific pest target. Describe what happens to the field if the pest is not controlled.
Q: Is it safe for me (or my kid) to be around what you are spraying?
This is a really hard question to answer because the meaning of the word “safe” is different for everyone.
The other part of the answer to this question depends on the length of exposure time after the pesticide was applied.
The easy answer is to state that since you are using a registered pesticide according to its label directions, users should be reasonably safe after the reentry period. Personally, I think it is risky to get into a lot of detail because of the danger of miscommunication.
However, a lengthier version of an answer to the question follows:
All pesticides have some level of toxicity because, as the name implies, they are designed to kill something. The actual risk associated with a particular product depends mainly on a couple of things.
One is its toxicity and the other is a person’s exposure to it. In the 1500s, the German physician Paracelsus summed it up best – I’m paraphrasing – everything is toxic if you are exposed to enough of it. For example, even oxygen and water have been known to cause death.
We use a standardized measure called the LD50 to express a substance’s toxicity. It is defined as the dose that is necessary to kill 50 percent of the test subjects. Typically, rats are used to approximate human response. It is measured in milligrams of substance per kilogram of body weight. Because of that, the lower the LD50, the more toxic the substance is because less of it is required to cause death.
If you look up LD50 values for the active ingredients in our pesticides that are registered today and compare it to other things we encounter in life, they are usually not spectacularly more toxic.
For example, the reported LD50 of glyphosate is 5,180 mg/kg. Compare this to things like table salt (3,320 mg/kg), bleach (2,000 mg/kg), caffeine (200 mg/kg), or gasoline (50 mg/kg).
I chose the example of glyphosate because it has one of the highest – and least toxic – LD50 values of any pesticide we apply.
This should make sense if you look at how it works. It acts to inhibit the formation of branched chain amino acids. Plants need to be able to do that and we do not.
Now, a couple of caveats to this line of thinking: 1) there are other substances in formulated pesticides that might be more toxic than the actual active ingredient, and 2) there are other active ingredients that are more toxic than glyphosate.
The signal word on the pesticide container is the guide to its toxicity. For example, most formulated products containing glyphosate carry a caution label, which means the LD50 is between 500 and 5,000 mg/kg. There are many pesticides that are more toxic, and so they will carry a warning (LD50 between 50 and 500 mg/kg) or a danger (LD50 less than 50 mg/kg).
There are many things around the house that are just as toxic as pesticides, such as antifreeze, motor oil, gasoline, battery acid, bleach and household cleaning products. As with any of those products, pesticides should be respected and we should be careful when we use them. Just like gasoline, pesticides can be dangerous when used improperly but are considered reasonably safe when used correctly.
A potential follow-up question or comment: Fair enough, but that tank seems pretty big, which means you are applying an awful lot of material.
Another important factor with pesticide safety is exposure, both short term (acute) and long term (chronic). The pesticide label contains a section called “Hazards to Humans and Domestic Animals” that gives an overview of the risks.
With acute exposure, unless the user comes into contact with the concentrate, they are unlikely to be poisoned by the pesticide. With one of our common herbicides, a 200-pound person would have to ingest about 4 gallons of formulated product to have a 50 percent chance of dying, which is not very likely.
Having said this, people can report symptoms such as dizziness, nausea and headaches as a result of exposure. On the product label, it states the amount of time necessary following application before the treated area can be re-entered. During this time, the residues dry and become bound to plant, soil and organic matter.
Most evidence available in the literature shows that bound pesticide residues do not come off of or dislodge from organic matter very easily. This varies by active ingredient. The risk becomes greatly reduced, but not completely eliminated.
Q: Is it true that a lot of pesticides are suspected of causing cancer or other health problems?
This is also a tough question because sometimes things we think are safe, including certain pesticide active ingredients, we later learn are not.
The effects of chronic exposure (long-term exposure to very small amounts) are much more difficult to study. And even if a product does pose a risk, determining if the risk is greater than exposure to other things in life (sunlight, air pollution, contaminants in drinking water, etc.) is in some cases nearly impossible.
In order for a product to be registered, it must be approved by the U.S. Environmental Protection Agency. In order for this to happen, the product must go through over 100 different health, safety and environmental tests to ensure that the product will not cause undue harm. Each one of these tests might involve research experiments in several states over a period of years to get a product registered for use.
Pesticides are also reviewed, and if there’s evidence that a particular active ingredient poses a risk, it is usually taken off the market.
But, again, this can be tricky because with certain products there may be some evidence that it causes health problems while other studies may indicate it does not.
The best course of action – once again – is to follow the label and laws that govern the application of the particular pesticide in order to minimize the risk.
Q: What happens to the product after you spray it?
In order for a product to be registered, the chemical company must show that the pesticide poses minimal risk to the environment when used according to the label.
Many of the pesticides labeled for use in turfgrass bind to organic matter in the soil, which minimizes or prevents leaching. The pesticide is then broken down into harmless compounds by microorganisms.
Certainly, this is a very gross simplification of pesticide fate processes. There are many other ways in which pesticides interact with the environment and are ultimately broken down.
But, again, in order to be registered, the chemical company must show that the product when used according to the label does not pose a risk of environmental contamination.
Q: Does the pesticide that you spray harm bees (or wildlife or fish or birds)?
All registered pesticides must be assessed for potential hazards to wildlife, including mammalian, avian and aquatic. Pesticides with too high of a risk are either classified as restricted use or are denied registration.
Bees are a different story. Certainly, this has gained much attention and, as pollinators for many of our food crops, for good reason. Most of the pesticides we apply are harmless to bees.
Damage due to the application of an active, harmful ingredient can be greatly reduced if spraying is avoided on areas that contain clover when the clover is in bloom.
This is one example of management recommendations that have evolved in order to help reduce potential non-target effects from the use of those insecticides.
The bottom line
The use of registered pesticides does carry some risk. However, if you follow the label exactly and follow all rules governing the application of pesticides in your location, then the use of registered pesticides is considered reasonably safe.
Users may ask questions about your use of pesticides. Thoughtful, educated answers can, in many cases, satisfy the concerns of end users of your fields.