Stormwater Management:
Pesticide Use in the Lawn and Garden
This NebGuide explains how the proper use and application of lawn and garden pesticides can prevent potential water contamination from stormwater runoff.
Erin C. Bauer, Extension Assistant
Clyde L. Ogg, Extension Educator
- Identify Vulnerable Areas
- Pesticide Selection
- Time Pesticide Applications
- Handle Pesticides Carefully
- Storage of Pesticides
- Pesticide Spill Management
- Equipment Maintenance and Cleaning
- Mixing and Loading
- Proper Disposal
Well-maintained lawns and gardens can create a beautiful, functional landscape around your home and provide shelter for a variety of wildlife. Through good cultural and integrated pest management (IPM) practices, the outdoor greenscape in the urban environment can remain healthy and thriving.
Along with proper plant selection and care, controlling pests in your lawn or garden is an important part of maintenance. Many cultural practices complement IPM control methods, such as:'
- planting varieties resistant to pest damage, disease, and drought;
- mowing turf at proper heights;
- efficient and appropriate watering practices; and
- judicious use of pesticides.
Pesticides should be limited where possible, but when necessary, use them responsibly. Always read and follow the pesticide label instructions before applying, such as with insecticides or herbicides, to reduce the risk of exposing humans or non-target animals. Take care to protect the environment, which includes the proper use of pesticides to prevent contamination of water resources.
An important aspect of prevention is managing areas where stormwater runoff may come in contact with pesticides and carry them to non-target sites. Since amounts and intensity of rainfall can vary greatly from storm to storm, it’s important to plan for the effects of runoff in the worst conditions and develop best practices for preventing runoff impacts.
Regardless of an applicator’s role (commercial applicator, homeowner or municipal employee), using pesticides properly and safely will go a long way in preventing contamination of stormwater runoff leading to contamination of water resources.
Identify Vulnerable Areas
When applying pesticides to the lawn or garden:
- Keep in mind vulnerable areas such as sandy soil, sinkholes, wells, streams, ponds or storm sewers, and avoid pesticide applications on sites near these areas.
- Be aware of potential access from sloping driveways or lawns into storm drains or backyard ponds.
- Observe the layout of the land. Sloping areas are far more prone to carrying stormwater runoff to non-target areas than flatter areas, and areas with heavier vegetation may buffer non-target sites better than areas with little vegetation.
- You may be able to create buffer strips near sensitive areas to soak in runoff and decrease the potential for water contamination. Buffer strips are areas of vegetation installed/maintained near or around a water source that are designed to capture pollutants, sediments, etc. before they reach the water source.
Another possible way to “capture” stormwater runoff and prevent it from going to non-target locations is to build a rain garden near vulnerable areas. A rain garden is a depressed, planted area that is designed to soak up excess rainwater. A strategically placed rain garden can greatly decrease the potential for contamination in other areas.
Pesticide Selection
Choose pesticide formulations that are less likely to leach, drift or run off the application site through stormwater to help prevent water contamination in sensitive areas. Pesticides with high water solubility, low adsorption (ability to bind to soil and plant surfaces) and persistence are more likely to cause water contamination. Read the pesticide product label for warnings about its potential to contaminate water, and follow label instructions about how to properly apply the product to avoid these problems. Contact your local University of Nebraska–Lincoln Extension office or the chemical manufacturer if you have questions or would like more information about selection of pesticides.
Time Pesticide Applications
When applying pre-emergent herbicides, time the application in anticipation of rain. Many other pesticides should not be applied if rain is in the forecast for the next 24 hours because stormwater runoff can pick up recently applied pesticides, become contaminated, and then flow into vulnerable areas. Other weather-related factors should also be considered. Avoid applications in windy conditions due to increased pesticide drift. Be sure to apply pesticides as recommended for best control.
Always make the recommended number of applications per year, and be sure to follow all label directions. If you apply too much pesticide at a time (over-application) or apply more times a year than recommended you increase the chance of pesticides being picked up by stormwater runoff and reaching non-target sites. Contact your local Extension office if you have questions or would like more information about timing of pesticide applications.
Handle Pesticides Carefully
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Part of protecting water and the environment is handling pesticides properly and carefully according to the label. Many labels will have environmental hazard statements regarding water, such as “Do not apply directly to water or to areas where surface water is present ...” or “Do not contaminate water supplies when cleaning equipment or disposing of equipment washwaters.” Similar warnings about groundwater also can be found on the label.
Water contamination results from either non-point source or point-source pollution. Pesticide applications that drift, leach or are carried by stormwater runoff to non-target sites and contaminate water are considered non-point source pollution. In these cases, the problem usually is found later and although an original source might be suspected, it isn’t necessarily known.
Point-source pollution, on the other hand, indicates that the pollution place is specific and known and occurs in “real time.” For example, someone over-applying liquid pesticide and then seeing it flow into a backyard pond would be generating point-source pollution.
Proper adherence to the pesticide label will help prevent accidental spread of pesticides and non-point source and point-source pollution. In addition, do not apply pesticides if a rain storm is in the forecast. This practice alone can greatly reduce the risk of non-point pollution from stormwater runoff.
To prevent other point-source pollution, avoid spills when possible. When spills occur, clean them up immediately to prevent further contamination. In addition, the following practices will help eliminate point-source pollution:
Mixing and Loading Pads (Figure 1). Use mixing and loading pads to prevent pesticides from entering the soil. Mixing and loading pads are areas set up for the express purpose of mixing and loading pesticides, and should be made of impermeable material, such as glazed tile, sealed concrete or heavy plastic. The mixing/loading pad can be permanent or temporary. The pad must have barriers on all sides high enough to contain any pesticide or water within the mixing area.
Back-Siphoning (Figure 2). Back-siphoning occurs when a hose that is being used to fill a spray tank reverses its flow, carrying pesticide back into the water supply. If a reduction in water pressure occurs when a hose is extended below the surface of a spray mixture, with no air gap between the hose and the pesticide, back-siphoning can occur. Keep an air gap to avoid back-siphoning, or use anti-siphon devices on garden hoses. Always handle, dispose and store pesticides according to the label.
| A |  |
B |  |
| Figure 2. Prevent back-siphoning of pesticide back into the water supply (B, right) by keeping an air gap or using anti-siphoning devices on garden hoses (A, left). | |||
Storage of Pesticides
Store pesticides in locations away from water sources and in places not easily flooded after a heavy rainfall. Make sure the storage building is in good repair, doesn’t leak and has sturdy shelving. Store pesticides out of reach of children and out of potential paths of runoff or flood water. Buy only the estimated amount you’ll need in a season to avoid storing larger quantities for a longer period of time.
Pesticide Spill Management
Promptly clean up any spills that may occur in storage areas, during mixing and loading, or at the application site. Quick action can prevent excess unwanted pesticide from moving to non-target sites.
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Proper pesticide spill management includes following the “3 Cs”: Control-Contain-Cleanup (Figure 3).
Control: In order to prevent a pesticide spill from contaminating non-target sites, it must first be controlled. This includes stopping the pesticide spill from getting worse by up-righting any overturned containers or bags, for example.
Contain: After controlling the spill, the pesticide should be contained so that it can’t spread beyond the area where the accident occurred. Both liquid and granule spills can be problematic. A liquid pesticide can move to a non-target location fairly quickly, and rainfall can make stormwater run-off an issue. Excess granules left at a spill site can later be carried by stormwater to water resources. Therefore, prompt containment of pesticide spills is extremely important.
Using material that will soak up the pesticide is the easiest way to clean up liquid, and granules can be swept or scooped up. Do not use a garden hose to wash a spilled pesticide off of a driveway or sidewalk into a street. Keep kitty litter or other absorbent material in your pesticide storage location for such emergencies.
If the spill accident happens near water or does get into water, you should contact the Nebraska Department of Environmental Quality (state agency responsible for protecting environmental resources) at (402) 471-2186 or (877) 253-2603; the Nebraska Department of Agriculture (state agency responsible for pesticide regulations) at (402) 471-2394; and the Nebraska Game and Parks Commission, (state agency dealing with fisheries and other wildlife) at (402) 471-1111. For emergencies you can contact the Emergency Highway Help Line for the Nebraska State Patrol at (800) 525-5555.
Cleanup: After the pesticide is contained, it should be cleaned up according to the label. Whether it’s a commercial pesticide or one available for homeowner use, always protect yourself with the appropriate Personal Protective Equipment (PPE) as recommended on the label when cleaning up a spill.
When faced with a pesticide spill, there are many phone numbers you can call for assistance. The pesticide label itself should have a 24-hour emergency help line. For larger spills, you can contact your county emergency office or CHEMTREC (800-424-9300), which handles questions about pesticide emergencies.
Specific cleanup recommendations include:
- Hard Surfaces, such as concrete. Use absorbent material, such as kitty litter, to absorb liquid pesticides. After absorption is complete, sweep the material and dispose of it in a plastic drum or similar container. Carefully sweep dusts and granules and dispose of similarly. You may need to neutralize the area using 30 percent bleach in water or hydrated lime (do not use together) and work into the area using a broom. Then use new absorbent material to clean up this solution, and dispose of it in the same container as for the pesticide.
- Soil, compacted gravel, or turf areas. Shovel up the contaminated area, including the first 2 to 3 inches of soil if applicable, and place in a plastic drum or similar container for disposal. Then cover the area with 2 inches of lime followed by fresh topsoil or gravel.
- Discard any disposable PPE and clean all equipment (away from water sources) that could have been contaminated during the spill cleanup process. Always read the label for directions about proper disposal methods.
- Consider keeping a “spill kit” available containing emergency numbers, PPE, shovel, bleach or lime, bag of absorbent material, and disposal drums stored where it is easily accessible in the case of a spill.
Equipment Maintenance and Cleaning
Before applying a liquid pesticide, carefully check the application equipment for leaks or faults that would prevent correct pesticide application. Worn or clogged nozzles or hoses could result in a misapplication and increased likelihood of pesticide drifting to an unintended site. Always check nozzles and spray equipment before making any pesticide application.
When applying liquid pesticides, drift is always a possibility. Prevent drift by using spray equipment that produces large water droplets. Large droplets are less likely to drift than smaller droplets. See the equipment manufacturer’s information for more details about the particular size of droplets produced by your application equipment.
Uncalibrated, granule-application equipment can over-apply pesticide granules, thereby increasing the chances of transfer off the targeted area (Figure 4). Always calibrate granule spreaders properly, and use a spreader with an edge guard, if possible. The edge guard prevents granules from flying onto non-target areas while applying the pesticide and offers an additional safeguard against misapplication.
Clean all application equipment after use, according to label directions, and clean it at the application site whenever possible. The solution created from rinsing equipment, which consists of water and left over pesticide, is called rinsate. Apply rinsate to sites defined on the label and carefully follow all label instructions.
Do not discharge water used to clean application equipment into the street, along roads, or into storm drains. This rinsate could contaminate other water sources.
Do not leave uncleaned equipment in the open where pesticide residue could be washed off during the next rain.
Mixing and Loading
Always mix and load pesticides at least 50 feet away from all water sources, and if possible, mix and load at the application site. Avoid mixing and loading if rain is in the forecast. Use a mixing and loading pad, as described earlier, to prevent potential contamination of the soil and movement of pesticides into water. Be especially cautious if mixing/loading near a well.
If it is located near an application site, groundwater can easily be contaminated if pesticides enter the well. When using granular formulations, avoid applying granules to sidewalks, driveways or other hard surfaces (Figure 5). If granules do land on these areas, remove them. Sweeping often leaves granules in cracks and crevices, so a leaf-blower may work best to move granules back onto a targeted site. Should rainwater reach the sidewalk before sweeping, it could carry granules into storm sewers or other non-target areas. Pesticide granules lying on the sidewalk are dangers to pets, children or wildlife, which may find them attractive.
Proper Disposal
Always dispose of pesticide containers and leftover pesticides appropriately.
Apply rinsate only onto labeled target sites, and never directly apply to areas near water, wells, ponds, sinkholes, etc.
Keep sidewalks, driveways and streets clean and free of pesticides, as well as storm sewers and other potential places where stormwater could carry pesticides into water sources.
By following the pesticide label instructions for proper mixing, loading and handling procedures, pesticides can effectively be applied to minimize stormwater runoff, drift or accidental pesticide spills, and without compromising surface or ground water quality. In addition, applicators should be cognizant of weather conditions when making pesticide applications, and should use integrated pest management practices and tested cultural practices wherever possible. Through such practices, and in combination with quality/sustainable design standards, the backyard greenscape can be well maintained and cared for, while also preserving the quality of our environment and water resources.
This publication has been peer reviewed.
Visit the University of Nebraska–Lincoln Extension Publications Web site for more publications.
Index: Water Management, Water Quality
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Lawn and Garden, Water Management
Issued April 2008
