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Bagworms and Sap Flow on Green Giant Thuja

Sap After Pruning Is Normal

Conifers bleed sap from fresh cuts during active growth. It seals the wound and stops within days. No treatment needed.

Bagworm Management

Hand-pick bags (easiest on small trees) or spray Bacillus thuringiensis (Bt) in early June when larvae are small. Contact insecticides (spinosad, permethrin) work on larger larvae. Pruning infested branches is unnecessary and causes sap flow.

Sap from Unpruned Areas?

If sap appears where no cut was made, suspect a twig borer or canker. Apply systemic imidacloprid (Bayer Advanced or Merit 75WSP) as a soil drench for borers. For cankers, prune 6 inches below symptoms and improve tree vigor.

Treatment Frequency

One soil drench of imidacloprid in spring protects all season. Contact sprays may need reapplication per label (usually 2–4 weeks).

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