Question and Answer

What is OE (Ophryocystis elektroscirrha)? Why am I seeing adult monarchs with deformed wings?

Ophryocystis elektroscirrha (OE) is a debilitating protozoan parasite that infects monarchs. Infected adult monarchs harbor thousands or millions of microscopic OE spores on the outside of their bodies. When dormant spores are scattered onto eggs or milkweed leaves by infected adults, monarch larvae consume the spores, and these parasites then replicate inside the larvae and pupae. Monarchs with severe OE infections can fail to emerge successfully from their pupal stage, either because they become stuck or they are too weak to fully expand their wings. Monarchs with mild OE infections can appear normal but live shorter lives and cannot fly was well as healthy monarchs. For more information on OE and the higher risk or OE associated with planting tropical milkweed, read our handout Potential risks of growing exotic (non-native) milkweeds for monarchs.

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