Harmful pesticide residues found in monarch food

A monarch caterpillar feeds on orange milkweed (Asclepias tuberosa) in Illinois. Credit: Deborah Seiler

Milkweed plants are vital for monarch butterflies and their larvae, providing nutrition to power their multi-generational migrations. Many of these plants have declined due to human development, prompting conservation organizations to encourage people to plant milkweed in an effort to boost endangered monarch (Danaus plexippus) numbers. But a study published recently in Biological Conservation has found that many milkweed plants sold in retail nurseries in the United States contain levels of pesticides that could harm the butterflies. Some 38% of the samples that the researchers gathered had levels of chemicals high enough to be detrimental to the ability of the butterflies to migrate and forage.

Read more at Xerces Society.