Pesticide StewardshipSite Prep/Planting/Maintenance

On Target: Simple Herbicide Practices Help Conserve Monarch Habitat

When it comes to eliminating unwanted plants on farms and in our backyard, there is no single approach. Herbicides are one tool that is very effective when used in the right place, at the right time, and in the right amount. The Keystone Monarch Collaborative outlines some practices for using herbicides to safely and effectively control unwanted plants while conserving the integrity of the habitat for pollinators.

Common milkweed adjacent to soybeans Photo credit: Wayne Fredericks, American Soybean Association

Identifying milkweeds and other wildflowers that support pollinators is paramount. Monarchs depend on milkweed. It is the only plant their caterpillars can eat. There are numerous species of milkweeds native to different regions of the country. The Monarch Joint Venture has created a document that helps landowners identify milkweeds common in each region. The USDA-NRCS Plant Database is another resource available to landowners and the technical guidance is provided for conservation planners and landowners who are working to protect and improve pollinator habitat.

Pollinator habitat next to corn Photo credit: Pete Berthelsen, Bee & Butterfly Habitat Fund

After identifying plants that support pollinators, take the necessary steps to preserve it from weed control measures. Areas such as road-sides, behind buildings, and other unproductive areas of fields are great places to support biodiversity and a flourishing monarch population alongside high-production agriculture. Employ targeted spraying by spot spraying only the problem areas; do not broadcast spray the entire area. Targeted spraying will enable farmers to effectively eliminate the unwanted plants while preventing the incidental transfer of herbicide droplets to other plants you want to protect. The National Pesticide Information Center recommends taking the following steps to prevent drift: 

  • Read and follow the label directions carefully.
    • The label may prohibit applications under certain weather conditions. Apply during calm weather conditions. High winds can increase the risk of drift.
    • Adjust your nozzle(s) and pressure to make bigger droplets. Bigger droplets fall faster, so they are less likely to drift with the wind.
    • Be sure that the product you are using is labeled for the specific area you are targeting.
  • Avoid applications when there is fog hanging in the air. It may indicate that a ‘temperature inversion’ may be taking place. That increases the risk of drift.
  • Applying some herbicides before hot weather can lead to vapor drift. That vapor can seriously damage nearby plants.
  • Direct sprays away from property lines. Keep the wand or hose as close as possible to the target.
  • Use your best judgment, with your unique knowledge of the site and the application equipment to keep the product on target.

By implementing these simple practices, farmers can effectively reduce the number of unwanted plants on their land while also supporting, enhancing, and protecting monarch habitat.