Leaf Miner on Arborvitae and Junipers

Leaf miners (Argyresthia cupressella) attack both arborvitae and junipers. The miner tunnels into the growing tip and kills it. Heavy infestation can make the entire plant look brown and dead. The adult is a moth. It is a silvery tan and is out only in the spring and early summer. Eggs are laid on the branch tips that are one or two years of age. Upon hatching the larvae tunnel into the leaf scales and mines/tunnels until winter or even the following spring. Once the larvae are finished feeding, they leave the mine and spin a cocoon (pupae stage) in the dead or still living foliage. Weeks later, adults emerge, mate and lay eggs to start another cycle of feeding.