Question of the Week – Parasitic Wasp Cocoon

This week, the question was: What is this brown oval object on the underside of this napa cabbage leaf?

This is the cocoon of a parasitic wasp (Microplitis plutellae) that attacks and kills diamondback moth larvae. This wasp will lay an egg inside of the caterpillar, where the wasp larva feeds before emerging from the mature caterpillar to spin its cocoon, killing the caterpillar in the process.

This week’s question is from Tom Bilbo, Extension Vegetable Entomologist.