Diagnosing Lilac Decline: Root Rot and Herbicide Injury

A 5-year-old lilac shows yellowing, curling leaves with brown spots, bark splitting, and bark loss after spring bloom. Nearby rose and Japanese maple died; white fungus found in soil.

Primary Suspects

• Root/wood decay fungus: White fungal growth in soil suggests root rot pathogen (possibly Armillaria or similar). Pale foliage and bark loss support vascular collapse.
• Herbicide injury: Sharp cuts on stem in photos indicate possible mechanical or chemical damage. Drift from lawn treatments or contaminated compost/manure can cause delayed symptoms.

Prognosis and Next Steps

Bark loss on main stem often indicates terminal decline. However, before removal:

• Test soil for herbicide residues and nutrient status.
• Contact county Extension for on-site evaluation.
• If replacing, solarize soil or select resistant species.

The healthy neighboring lilac suggests localized soil issue rather than regional epidemic. Prioritize soil testing before replanting.