From the April issue of SportsTurf, here is Pamela Sherratt of Ohio State answering 2 questions; one about how to talk about using pesticides with clients, and one about organic weed control methods.
During any conversation like this, it’s essential that everyone agree that the safety of the athlete and the performance of the field are the main goals. Those goals are achieved by having a sound IPM program in place, which should ultimately limit the amount of weeds, pests and diseases on the field. Showing your clients that you have a strong IPM program, you have field assessment documentation, like the STMA’s PCI, and are perhaps working toward the STMA Environmental Certification, will all add credibility to anything you have to say. Even so, be prepared for someone in the meeting to be completely intolerant of pesticides, because sometimes it isn’t about facts, it’s about perception.
If you deem it necessary to apply a pesticide if, for example, there is grey leaf spot disease and the turf is dying, explain what will happen if you do not act. Also state what you are applying. You are legally required to explain what you are spraying and have the safety data sheet (SDS) onsite. Answering the question about the safety of pesticides in relation to people, animals, and the environment is a little more complex, because the word “safe” means different things to different people. The term “risk” is perhaps more appropriate.
Pesticides are regulated by the EPA and have gone through more than 100 different health, safety and environmental tests over several years. Explain that you use registered pesticides according to the label directions that, after the reentry period, should be reasonably low risk. A lengthier explanation on toxicity (LD50) and exposure could also be given if the situation calls for it. Be prepared for questions about whether a pesticide causes cancer, about the effects on wildlife (particularly pollinators) and about water contamination. Thoughtful, educated answers can, in many cases, satisfy concerns that field users might have. I have added information at the end of this piece about articles and PowerPoint presentations developed by Ohio State weed scientist Dr. Dave Gardner that you are welcome to use.
In relation to organic herbicides, the EPA keeps a list of active ingredients that are eligible to be considered minimum risk products. These are exempt from federal registration and thus do not have an EPA registration number. Commonly seen active ingredients for weed control in turf that appear on this list include corn gluten meal and sodium chloride. The EPA also has a list of approved biopesticides. These are reduced risk products but do not meet the criteria necessary for EPA exemption. Chelated iron, acetic acid, and pelargonic acid are examples of herbicides in this category. So if you are considering the use of organic herbicides because a law was passed in your area that says you have to, you need to check specifically as to what products you are allowed to use.
The majority of products from the EPA minimum risk list are non-selective, including cinnamon oil and eugenol. Biopesticides like acetic and pelargonic acid are also non-selective and very fast acting. Since they are contact herbicides they may require repeat applications for perennial weeds.
For preemergence weed control, corn gluten meal (CGM) is the option for crabgrass and dandelion control, applied twice during the season. CGM contains 10% nitrogen and no phosphorus or potassium. The recommended rate of CGM is 20 pounds per thousand square feet. This application thus provides 2 pounds of slowly available nitrogen, and applying in both fall and spring would provide 4 pounds of your annual nitrogen fertility requirements. Note: CGM will have preemergence activity on grasses, like perennial ryegrass, and results appear to be more successful in the second and subsequent years of application. If you are considering or are required to switch to an organic field maintenance program then corn gluten meal should probably be the foundation of your fertilizer and herbicide management program.
Currently, there are no solid organic options for selective postemergent control of grasses and sedges. For postemergence control of broadleaf weeds, two organic products that are registered are sodium chloride (A.D.I.O.S.) and chelated iron (Fiesta). A.D.I.O.S. offers some short term but variable control. The product is also somewhat injurious to grass, though less so in the fall. You will also want to test your soil to make sure that use of this product is not going to result in too much sodium, which can damage the desired turfgrass. Fiesta is a contact herbicide that can potentially give up to 100% control of dandelion within 24 hours of application. It also works rapidly on weeds such as white clover, the plantains and ground ivy. Control is typically in the 75-90% range. While this might be effective with one application if targeting young annual broadleaf weeds, for perennial broadleaf weeds control is only of the top growth and the weed typically begins to recover within about 3 weeks.
Organic weed control in turfgrass has advanced considerably but there are still some management challenges. Speed of control can be just as good or better compared to synthetic herbicides. However, duration of control and completeness of control lags that of synthetic herbicides. Some of these products are very safe to turf, such as corn gluten meal. On the other hand, there are other organic products that you still have to be careful about non-target injury. Lastly, while prices have come down, organic options tend to be more expensive than their synthetic counterparts.
From Dr. Gardner: “Communicating with People about Chemical Applications” and “Organic Vs. Synthetic Herbicides for Athletic Field Weed Management” can be accessed here.