Conservation Practices for Monarch Butterflies

By Rainer Hoenicke

Natural Resources Conservation Service (NRCS) biologist, Jennifer Kubel, presented a webinar on August 26, 2020, on agricultural and horticultural practices that could benefit Monarch butterflies. As many of us know by now, the western population has declined drastically by more than 90% since the 1980s. What can landowners do to help? That was the key topic of the webinar. While the intended audience was mostly agricultural producers that operate on much larger scales than horticulturalists and hobby gardeners, many of the conservation practices are applicable even at small scales.

Key factors related to the decline of Monarchs are overwintering habitat loss along the coast, breeding and migratory habitat loss, as well as direct and indirect pesticide impacts. Master Gardeners can certainly contribute to spreading the word about applicable practices that can reverse at least two of the key factors of butterfly declines. The information resources that NRCS offers via the agency's website are immense. Many of them are on platforms that are map-based and interactive, such as e-Veg Guide at www.calflora.org/nrcs. That guide can show the various plants and their blooming times that benefit Monarchs during their migration times. The NRCS also has easily accessible technical guides with information about the conservation of soil, water, air, and related plant and animal resources (https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/technical/cp/ncps/?cid=nrcs143_026849). Each conservation practice is listed alphabetically and by number. Jennifer provided a brief overview of each applicable practice, among them Wildlife Habitat Planting and Conservation Cover (#420 and #327, respectively), Hedgerow Planting (#422), and Restoration of Rare or Declining Natural Communities (#643). Certain trees and shrubs can provide year-round beneficial monarch habitat for nectar, shelter, shade, and roosting. Coyotebush, e.g., is an important nectar plant from late summer through winter. If concerned about seed spread, you can buy male plants only at nurseries.

She also discussed direct and indirect pesticide impacts on Monarchs. The current generation of extensively used insecticides, called neo-nicotineoids (or “neonics”), have been detected in plant tissues at concentrations that can impact feeding larvae and contribute to their already high mortality rates (https://www.frontiersin.org/articles/10.3389/fevo.2020.00162/full ).

Neonics degrade only slowly, with a half-life of up to 280 days in soil (https://www.researchgate.net/figure/Half-life-in-Soil-of-Neonicotinoids_tbl1_233795128).

An example of indirect pesticide application impacts is that of applying broad-spectrum weed killers that milkweed species are particularly sensitive to (e.g. Roundup).

Jennifer also listed the native California milkweed species and their bloom times. Asclepias californica and A. cordifolia are early-blooming species, unlike the more commercially available species of showy and narrow-leaf milkweeds that bloom mid- to late-season. Asclepias cordifolia and A. eriocarpa are extremely tolerant of dry, rocky terrain and can survive the dry season without irrigation just fine.  The Xerces Society has a milkweed seed-finder on their website, in case you want to create your own milkweed patch in your back yard or get one established in your sidewalk strip, instead of that thirsty Dichondra lawn (https://www.xerces.org/milkweed/milkweed-seed-finder).

Master Gardeners are following recommended social distancing guidelines that keep everyone safe, Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

Photo credits: Courtesy of Idaho Dept. of Fish and Game