What does classifying monarch butterflies as a threatened species mean for farmers?

Anthony Hanson, PhD - Regional Extension Educator - Field Crops IPM

Recently, the US Fish and Wildlife Service (USFWS) announced a proposal to designate the monarch butterfly as a "threatened" species under the Endangered Species Act. This summary of that proposal is meant as an educational aid for understanding what the "threatened" status proposal is suggesting related to farming practices. A public comment period is open until March 12, 2025. After the public comment period, USFWS will make a final determination up to one year later on whether to list the butterfly as threatened after evaluation of comments and any additional information about this species.

Monarch caterpillar feeding on milkweed in Stearns County, MN. Photo: Anthony Hanson

During the winter U of M Extension meeting season, a number of farmers have asked how their pest management planning might be affected by the proposed rules or what those rules entail. What does this mean for farmers and integrated pest management for insect and weeds, especially in Minnesota? The short answer is that threatened status (likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range) has different implications than the much more stringent endangered status (in danger of extinction throughout all or a significant portion of its range). The North Central IPM Center had a good summary of what the current threatened status proposal entails if accepted as currently written:

Under the proposed "threatened" status, these activities would still be allowed:

• Maintenance, enhancement, removal or establishment of milkweed and nectar plants within the monarch's breeding and migratory range
• Implementation of conservation plans developed by state or federal agencies
• Maintenance or improvement of monarch overwintering habitat in the United States when following an approved plan
• Non-lethal collection, possession, captive-rearing, and release of 250 or fewer monarchs per year
• Non-lethal scientific research and educational activities involving 250 or fewer monarchs per year
• Possession of dead monarchs
• Sale of 250 or fewer captive-reared monarchs

Two primary questions I had as an entomologist from the pest management perspective when I first heard about this proposal is how would this affect weed management where milkweed (i.e., both a weed and a host plant for monarch butterflies) is present, and how would the rule affect insecticide use? Below, excerpts from the USFWS proposal are included that help summarize what is proposed specifically for agricultural use. Overall, it appears milkweed can be removed from agricultural fields under the proposal with some specific details about how that is done currently undecided:

(1) Activities that may maintain, enhance, remove, or establish milkweed and nectar plants within the breeding and migratory range that do not result in conversion of native or naturalized grassland, shrubland, or forested habitats.

These activities include the following:

(a) Habitat restoration and management activities, such as mowing and haying native rangeland, that sustain monarch butterfly habitat, including activities to eliminate plant communities that contain invasive plants or noxious weeds as part of site preparations or habitat enhancement activities.

(b) Livestock grazing and routine ranching activities, including rotational grazing, patch-burn grazing, vegetation and invasive species management, other grazing practices implemented to make pasture and rangelands productive, construction and maintenance of fences, the gathering and management of livestock, and the development and maintenance of watering facilities for livestock.

(c) Routine agricultural activities, including plowing, drilling, disking, mowing, and other mechanical manipulation and management of lands already in use for agricultural production ( e.g., conventional row crops, pasture, hay fields, orchards, and vineyards). This also includes other mechanical manipulation and land management activities in direct support of cultivated agriculture, such as replacement, upgrades, maintenance, and operation of existing infrastructure (e.g., buildings, irrigation conveyance structures, fences, and roads), and routine implementation and maintenance of agricultural conservation practices, such as terraces, dikes, grassed waterways, and conservation tillage.

In the proposal, USFWS considers routine agricultural activities on lands already in use for agricultural production as not likely to lead to additional habitat loss and degradation. However, pesticide use is another routine agricultural activity that is not specifically included in the listed examples. Instead, as part of the public comment request, the proposal asks if exceptions for allowing pesticide use should be included:

Whether [USFWS] should include an exception for the use of pesticides and, if so, what measures are reasonable, feasible, and adequate to reduce or offset pesticide exposure to monarchs from agricultural and non-agricultural uses (e.g., rangeland, rights-of-way, forestry, commercial areas, and mosquito control), including measures for specific classes of pesticides ( e.g., herbicides, insecticides), pesticide uses, and application methods. . .

USFWS then asks for specific pesticide uses that may be of concern that may need mitigation or where "take" (i.e., monarch losses) is considered minimal:

We recognize that certain types of pesticide use can have direct or indirect negative effects on monarchs, including aerial broadcast application of insecticides, use of herbicides that remove milkweeds, and use of some biopesticides. However, not all uses and application methods will impact monarchs. For example, insecticide application using hand-held sprayers, soil injection, in furrow sprays, tree trunk drenching, or tree injection, are unlikely to result in pesticide exposure to monarchs. We seek comment on which pesticide uses and application methods result in exposure and adverse effects to monarchs, whether to except take from those uses in a 4(d) rule, and whether the exceptions for those uses should include measures to mitigate the effects of pesticides on monarchs. We also seek comment on whether we should tailor any measures according to the areas and times of the year when monarchs are present and, if so, what is the most feasible method to convey this information to pesticide users.

Other types of pesticide use, especially direct herbicide and fungicide exposure, aren't considered to significantly affect monarchs, and part of USFWS' focus is instead on improved habitat to offset other losses:

For other pesticide classes, such as herbicides and fungicides, our review of the scientific information available indicates a limited number of individual monarchs will experience negative effects from direct exposure to these pesticides. We do not expect the low number of individuals affected from direct exposure to other classes of pesticides to impact the monarch butterfly at a population or species level. Certain herbicide uses, however, have resulted in the loss of milkweed and nectar, which is discussed in the Activities that may maintain, enhance, remove, or establish milkweed and section. As a result, we are considering what mitigation measures, if any, from the EPA's Herbicide Strategy (EPA 2024a, entire) and the agency's other ESA work (EPA 2024b, entire; EPA 2024c, entire), should inform any exceptions for herbicide use in a 4(d) rule for the monarch. Further, the EPA is considering how habitat restoration and other forms of compensatory mitigation may address unavoidable pesticide impacts to listed species. We thus seek comment on whether and how we should consider habitat restoration or creation as an offset for unavoidable pesticide impacts to the monarch under a 4(d) rule. 

The final determination may differ from the current proposal after the comment period, and based on any new information, USFWS may conclude monarch butterflies are instead endangered instead of threatened, or they may decide it does not warrant listing as either an endangered species or a threatened species. 

In short, this is a proposed rule and is not finalized yet. At least based on the current proposal, milkweed can still be managed as a pest, but what isn't clear in the proposal yet is how pesticides may be used in farming where monarchs may be present whether that be for weed or insect management. That will be determined through the public comment process. Portions of the proposal also discuss other factors not discussed in this summary such as climate and other habitat issues monarchs face. The full proposal can be found at: https://www.regulations.gov/document/FWS-R3-ES-2024-0137-0001.