Pesticide use
MnDOT is committed to using effective strategies to manage pests on our property. MnDOT uses pesticides on MnDOT property as an important part of Integrated Pest Management (IPM) in accordance with Governor Walz’s Executive Order 19-28. IPM is an economic and ecosystem-based strategy that focuses on long-term pest control and prevention. MnDOT ensures safe environments by controlling dangerous and unwanted pests on its roadsides, building structures and building grounds and must balance public health risk, ecological risk, and effective property management.
Within MnDOT, we typically limit pesticide use to include
- Fungicides, used to control fungi and mold;
- Herbicides, used to control dangerous or unwanted vegetation including but not limited to species listed under Minnesota’s Noxious Weed Law;
- Insecticides, used to control or repel insects from vegetation at high risk on infestation or to control insects that pose a threat to the public;
- Rodenticides, used to control rodents.
Herbicides
MnDOT manages vegetation on approximately 175,000 acres across Minnesota. Unwanted woody vegetation (brush) and noxious weed management on this scale requires MnDOT to seek cost effective solutions. Herbicides often provide that cost effective solution to provide weed control efficiency that more labor and time intensive solutions cannot match.
Labor intensive solutions do not always provide the best outcome nor are they always cost efficient. One visit and one application of herbicide, for example, can often prevent plants from maturing to flower and seed development. Mowing on the other hand would likely require multiple, frequent visits to provide the same level of control in regards to stopping seed production.
MnDOT herbicide applicators are trained, many are licensed through the Minnesota Department of Agriculture (MDA). Training occurs in-house for all applicators. In-house training includes integrated pest management, pesticide labeling, personal hazards and first aid, personal protective equipment, storage, incident management, impacts pesticides have on the environment, proper application, and record keeping. Licensed applicators have passed required exams administered by MDA. To maintain their licensure, applicators are required to attend additional on-going training courses.
Insecticides
MnDOT does not regularly use insecticides on our rights of way. Seldom, MnDOT uses insecticides to protect high value vegetation at risk of infestation, such as large ash trees within an Emerald Ash Borer quarantine near MnDOT buildings have been treated for Emerald Ash Borer. We also use insecticides on insects which are a threat to public health such as wasp nests on rest area buildings. MnDOT does not use neonicotinoids if other insecticides are available.
Pollinators and pesticides
Native pollinators depend on native wildflowers and flowering shrubs and trees for food. Many invasive species, including buckthorn, wild parsnip, spotted knapweed, Canada thistle, and leafy spurge, degrade pollinator habitat by crowding out native wildflowers. Some of these plants even release a chemical to inhibit growth of other species near them. Controlling weeds along roads can improve roadside habitat and can also prevent infestations from spreading beyond the roadside where they could harm much more habitat.
Although herbicides are not directly toxic to insects, both herbicides and mowing can remove wildflowers (forage and shelter) and should be used carefully. Weed control efforts balance the short-term impacts to pollinator habitat with the long-term benefits of reduced invasive species infestations and improved wildflower populations. MnDOT limits the use insecticides to areas where there is potential harm to humans or structure (ie rest areas). When insecticides are used, they are used in small quantity and applied only to the spot needed.
MnDOT has created a weed identification book that is heavily used by our maintenance forces to make sure they are controlling the correct plant. This booklet provides pictures and descriptions of the state listed noxious weeds and also some of their look-a-likes for comparison. We also have a number of people within the department who are very good at plant identification to assist if the booklet doesn’t answer their question.