On true firs, which pests are commonly found that produce sooty mold and sticky residues?

• A. Bow-legged aphid and balsam twig aphid.
• B. Pine needle scale and spruce aphid.
• C. European pine shoot moth and hemlock woolly adelgid.
• D. Silver spotted tiger moth and balsam woolly adelgid.

Answer: (A)

On true firs, sticky residues and sooty mold come from honeydew produced by sap-sucking insects feeding on the tree. The pests most commonly associated with this on true firs are the bow-legged aphid and the balsam twig aphid. They feed on young growth and needles, excreting honeydew that supports sooty mold and leaves a sticky film on the foliage. The other options describe pests that either attack different hosts or cause different signs (like defoliation, woolly masses, or needle-scale issues) rather than the honeydew-driven sooty mold you’d see on true firs.