Identifying and Controlling Bagworms on Cypress Trees

What Are Bagworms?

The spindle-shaped, camouflaged “cocoons” hanging from your cypress are bagworms (Thyridopteryx ephemeraeformis). Larvae construct bags from silk and plant debris, feeding with only their head protruding. They infest many conifers and deciduous trees.

Control Methods

Mechanical

Hand-pick and destroy bags if the tree is small enough.

Biological

Apply Bacillus thuringiensis (Bt) in late June after all eggs have hatched and larvae are young.

Chemical

Stomach insecticides (acephate, bifenthrin, carbaryl, chlorpyrifos, diazinon, malathion, etc.) work if foliage is thoroughly covered. Spray early when larvae are small.

Bagworms have one generation per year; timely intervention prevents defoliation.