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Omaha symptom guide

What If I See Insects, Bags, Webbing, or Sticky Residue?

Visible insects or structures can be useful evidence, but presence alone does not show whether the organism caused the tree’s decline or whether treatment is warranted.

Sources checked: 2026-07-26Next source review due: 2027-01-26Independent professional review: not completed

What this page is for

Organize the observation before choosing action

Turn a visible insect observation into safe, useful documentation, not a pesticide recommendation.

This page does not identify the cause, recommend chemical treatment, or determine that pruning or removal is needed.

What to notice

  • Record the host tree, plant part, number and distribution of insects or structures, and whether feeding damage is nearby.
  • For bagworms, life stage and population matter; for bark borers, host and hole shape matter, since emerald ash borer leaves D-shaped exit holes and other ash borers leave round ones.

Plausible categories to compare

These are not ranked probabilities and do not form a diagnosis.

Defoliating or sap-feeding insects

Leaf loss, sticky honeydew, bags, or webbing can come from different insects or mites, so host and life stage matter.

Bark or wood-boring insects

Holes and galleries can help narrow borers, but tree stress and look-alikes still matter.

Non-pest material or secondary activity

Not everything on a tree caused its problem: fungus growing on the surface may be feeding on organic matter and unrelated to the damage, and debris collects in webbing.

What to document from the ground

  • whole tree and host features
  • affected branch or trunk area
  • close-up from more than one angle
  • safe scale reference
  • count/distribution and date first noticed

Safety boundary

Do not climb or spray from this guide. Keep clear and use Hazard first if insects are on a hanging limb, split trunk, moving tree, or near a power line.

Use the Hazard Assessment

Related named references

These names are useful for further research, not confirmation of what is affecting a specific tree.

BagwormsEmerald Ash Borer (EAB)Apple Scab

Sources