Ventura County Bans Sale of Tropical Milkweed to Protect Monarchs

Published by Anne Russell on

Because of its role in spreading disease among Western monarch butterflies, tropical milkweed

Tropical milkweed

Tropical milkweed is a non-native monarch butterfly host.

(Asclepias curassavica) has been classified as a “noxious weed” by the California Department of Food and Agriculture. That led to a June 1 notice of a ban by Ventura County Agricultural Commissioner Ed Williams on its sale by nurseries and other retailers.

The popular yellow-and-red flowered garden plant is a non-native that doesn’t go dormant during the winter, unlike the native narrowleaf milkweed (Asclepias fascicularis). Tropical milkweed harbors a parasite called Ophryocystis elektroscirrha that preys on monarchs. More commonly known as OE, the parasite’s spores are carried on and spread by adult monarchs as they migrate.

As monarch caterpillars hatch and feed on effected plants, they ingest the OE spores and become infected with the parasite. OE infections are linked to reduction in body mass, diminished reproductive success, and, ultimately, shortened lifespans. The sharp declines seen in the Western monarch population since the 1990s are in part due to OE.

Although the newly enacted ban applies only to the retail sale of tropical milkweed, Jackie Nuñez, a spokesperson for Ventura County’s executive offices, says, “Anyone who wishes to remove this plant from their properties is encouraged to do so.”

Image by Kimberly Frantz/Pixabay


3 Comments

View Betina Loudermilk’s talk about the plight of the Western monarch butterflies and what you can do to help them survive. – Conejo Open Space Foundation · 06/10/2022 at 3:08 pm

[…] captive monarch raising—an important fact to be aware of. Another important legal change is the new ban on tropical milkweed sales in Ventura […]

View the recording of Betina Loudermilk’s talk about the plight of the Western monarch butterflies and what you can do to help them survive – Conejo Open Space Foundation · 08/14/2022 at 11:24 am

[…] captive monarch raising—an important fact to be aware of. Another important legal change is the new ban on tropical milkweed sales in Ventura […]

Native Plantpalooza & Eco Fest Stages a Successful Return October 7; See the gallery of photos! – Conejo Open Space Foundation · 10/11/2023 at 5:36 am

[…] and Ventura County. Sanchez explained to the audience how to grow narrowleaf milkweed from seed and why tropical milkweed is not a good option for supporting the Western […]

Leave a Reply

Avatar placeholder