Diagnose: Arborvitae Bagworms

1. Bagworm caterpillars feeding inside silk cases shingled with the arborvitae's own foliage.
2. Take hold of one of the hanging shapes and pull gently. A bagworm case is tied on with a band of silk and resists, where a cone or a scrap of debris comes away in your fingers. Then measure it. Anything under two thirds of an inch means the larvae are still young enough for a biological spray to work, and anything larger means the window has closed and you are handpicking instead. If the browning has no cases attached to it at all, look at arborvitae winter burn before you treat for anything.

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