Environmental Protection

Management Practices

Proper Use of Pesticides, Herbicides, and Fertilizers

The University is a heavily developed complex of buildings and paved open spaces, much like Ann Arbor, the city in which it is located. Yet, both the University and the city have many open spaces, including athletic fields, golf courses, the Arboretum, and green open plazas. More important are the often overlooked small grass surfaces, planting beds, and those small areas of remaining vegetation. Both large and small open spaces are potential sites for contaminated water runoff or infiltration. It is obvious that silt and debris can potentially contaminate stormwater runoff from these areas; however, the not so obvious stormwater and groundwater contamination that can result from chemical applications is also a major concern.

Chemicals that may potentially migrate into our drinking water supplies are pesticides, herbicides, and fertilizers. In all cases, stormwater runoff containing these chemicals causes problems. Surface runoff of pesticides and herbicides into water bodies changes natural ecosystems by killing or damaging a wide variety of organisms. They often collect and accumulate in the food chain, becoming more harmful than their ambient concentration would suggest. Fertilizer can also disrupt natural biological communities by increasing plant and microbial growth. This condition, known as eutrophication, can drastically change natural water ecosystems and create new pollution conditions.

Improper application of pesticides, herbicides, and fertilizers may also have an impact on stormwater infiltration into groundwater. When these contaminants dissolve in stormwater they find their way into the groundwater and then into surface waters, such as ponds, streams, rivers, and lakes. The infiltration of these chemicals may also contaminate soil and deeper groundwater units.

Using Pesticides and Herbicides
The risk of using pesticides and herbicides is greatest when the directions are not followed exactly. Carefully read product labels, which contain information about the persistence and toxicity of the chemical. The words “natural,” “organic,” or “biodegradable” do not guarantee that it is safe. Always choose a “pest-specific” pesticide or herbicide that is designed to kill only the pest causing the damage. Persistence refers to the length of time it takes to break down to one-half its previous concentration (also known as half-life). The half-life should be printed on the product label. Avoid pesticides with half-lives longer than 21 days.

In dealing with pesticides and herbicides at home or on the job, develop a plan for use and safety. At work, only certified applicators may use pesticides and herbicides. On campus, Pest Management and Grounds & Waste Management (G&WM) handle application of these chemicals. If you have a concern contact OSEH for guidance and assistance in their proper use. Be extremely careful with the storage of chemicals: problems with leaks, spills, and inadvertent accidents with pets and children have resulted in many tragedies.

The University employs Integrated Pest Management (IPM) methodology, an ecological approach to pest management, to control pesticide and herbicide application in University buildings and on its grounds. All available techniques are used to reduce pest populations to acceptable levels while minimizing the potential impact of pesticides and herbicides upon humans and the environment. All soil that the U-M fertilizes is tested prior to any application of fertilizer. Fertilizers shall be applied only in accordance with soil test results and recommendations.

To further minimize the discharge of pollutants to the stormwater drainage system, Grounds & Waste Management maintains a chemical free buffer strip in lawn areas that border any streams or ponds and all priority 3 lawns are currently left untreated.

Mixing and Use of Pesticides and Herbicides
The mixing and use of pesticides and herbicides is of major concern because this is the time at which many spills occur. It is critical to follow instructions for mixing and use exactly. Be concerned with cleanup and disposal at all times during the use process. Any leftover chemical, the storage containers used in all stages of the application process, and the application equipment must be considered in the cleanup process. Some Guidelines to follow when using pesticides and herbicides include:


  • Always wear appropriate protective clothing. Never wash contaminated clothing with other clothing.
  • Take precautions to prevent spills. For example, close containers tightly after each use, even if you plan to reopen them soon.
  • Know what to do if a spill occurs.
  • Mix only the amount needed for the job.
  • Follow the directions on the label exactly.
  • Avoid spraying over impervious surfaces.
  • Do not spray on a windy day.
  • Do not apply to bare or eroding soil.
  • Do not apply near water systems such as wells, streams, and lakes. Reduce cleaning and waste by clustering jobs that use the same solution.

Pesticide and Herbicide Storage
Keep pesticides and herbicides in their original containers so you know what they are and how to use them. Mark the date of purchase on each container and use older materials first.

If possible, store pesticides and herbicides indoors in a clearly marked area, designed as secondary containment. Storage areas should be located at least 150 feet from any drinking water well and at least 200 feet from any area that holds water, even intermittently, such as a drainage ditch or dry retention pond.

Pesticide Storage Pesticide Storage

The pesticide storage area (left) and mixing shed located at the North Campus Grounds Service Facility demonstrate proper pesticide mixing and storage procedures.

Cleaning and Disposing of Empty Pesticide and Herbicide Containers
According to the Washtenaw County Extension Service, the best methods for cleaning containers and equipment are to triple rinse or pressure rinse in the field. To triple rinse: allow the concentrate to drain from the empty pesticide container for 30 seconds. Fill one-quarter of the container, replace the lid, and shake the container so that all interior surfaces are rinsed. Drain the rinse water into the spray tank for at least 30 seconds. Repeat the process twice for a total of three rinses.

Rinse water must be collected and applied to a compatible site at or below the labeled rate. Empty pesticide and herbicide containers cannot be refilled, reconditioned, recycled, or sent back to the manufacturer. They must be crushed, broken, or punctured so that they cannot be used again.

In general, small containers that are used in the home can be disposed of in the trash pickup after they have been rendered unusable and then wrapped in plastic.

Leftover pesticides and herbicides used in residential settings may be disposed of at the Washtenaw County Home Toxics Center free of charge at 705 N. Zeeb Road. For more information call (734) 222-3950. Toxins to be disposed must be in sturdy containers. Milk jugs are not acceptable, their plastic is to thin. Pesticide used on campus can be disposed through OSEH EHMM.

Using Fertilizers
The University employs horticulture specialists to manage fertilizer usage on campus property. Overuse of fertilizers can be detrimental to the intended use of an area. As an example, too much nitrogen will cause plants to produce shallow roots, a condition not conducive to athletic uses such golf or football.

Applying unnecessary amounts of fertilizer is not only a waste of money; it can also be detrimental to water quality. Excess fertilizers can wash into waterways, stimulating nuisance weed and algae growth. Excessive plant growth can choke slow moving waters, take up oxygen needed by fish and other aquatic life, and release ammonia which is toxic to fish. Before applying fertilizer, have the soil tested to determine what nutrients must be added. Residential soil testing can be through the Washtenaw County Cooperative Extension Service (971-0079).

To learn more about the University’s use of safe fertilizers, in particular soybeans, please visit the G&WM page Using Soybeans as Lawn Fertilizer.

Apply fertilizer at the proper time. Lawn fertilization programs should begin in early October, not early May. When applying fertilizers, follow the directions exactly and keep fertilizers off paved areas. If a liquid fertilizer is used, be careful to avoid over spray and drift. Sweep granular fertilizer back onto the grass to keep it from being washed into the stormwater drainage system.

Healthy trees and shrubs do not require annual fertilizing. If woody plants appear unhealthy it may be due to poor soils, insects, disease, or current weather patterns. Fertilizers should be applied only when a tree or shrub is growing poorly and the problem can’t be traced to other causes. If trees or shrubs do need fertilizer, apply it when the plants are dormant in late fall or early spring. Fertilizing in early fall or late spring stimulates growth that was previously limited by depleted stored food supplies and the plant’s inability to survive harsh winters and summers. Over-fertilized shrubs will actually produce more growth and in turn require more pruning.