Parsnip Webworm Moths
Many people are familiar with the invasive Wild Parsnip’s (Pastinaca sativa) ability to cause a chemical burn on human skin when the skin is exposed to sunlight. The compound that causes the burning and blistering (furanocoumarin) is in the plant’s sap, and thus is present in the leaves, stems, flowers and fruits of Wild Parsnip.
What is lesser known is that there is a non-native moth (Parsnip Webworm Moth, Depressaria radiella) that was introduced to the U.S. in the 1850’s whose larvae feed on Wild Parsnip. As a result of this herbivory Wild Parsnip upped its chemical arsenal and started producing more concentrated furanocoumarin.
What humans avoid, Parsnip Webworm Moth larvae take advantage of. Most of the plant toxin these larvae ingest is excreted in their feces. Some, however, is incorporated into the caterpillar’s silk webbing which encases the flowers and seeds that they eat, serving to protect the larvae from predators.
The adult Parsnip Webworm Moth is about half an inch long and is brown with black flecks.
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