Stem miner (Lepidoptera: Opostegidae) in Agastache

Affected stems, observed in mid-July, showed long narrow linear mines up and down their length, as well as localized areas in the upper stems that were more intensively mined. The long narrow linear mines were extremely thin and slightly raised above the surrounding tissue, and they were a greenish color with frass not easily visible. There was a bulging, gall-like distortion to the stem tissue in the more intensively mined localized areas in the upper stem. It appeared that larvae had constructed the long narrow linear mines lower on the plant when they were younger, and finished their development in the localized blisters in the upper stems. Pupation occurred off the plant in an oval, rusty-colored cocoon. I reared adults in mid-August from larvae collected in mid-July.