Wax Myrtle Stem Growths: Disease Complex Requiring Pruning and Monitoring

Symptoms

Don (Brevard County, FL): small black growths on wax myrtle stems, rough protrusions. Scraped: wet, purplish. Sprayed 50% malathion (3 tbsp/gal) — some drying of growths. Infected branches have black mold on leaves but not dying.

Disease Complex Identified

• Pests: Caterpillars, webworms, mites (webworms common — prune out)
• Lethal diseases: Avoid unnecessary pruning (wound entry)
• Cankers: Ptychogaster canker on old branches/trunks → kill tree
• Fusarium wilt: New in central/south FL — Fusarium oxysporum/spp.
• Sphaeropsis gall: East FL — wet weather spread, branch dieback
• Control: Prune infected branches to clear wood
• Inonotus heart rot: Decays oldest xylem
• Mushroom root rot: Causes decline
• Short-lived species due to disease susceptibility

Malathion Note

Partial drying of growths after spraying suggests insect component (scale?) but diseases dominate. Malathion won't control fungi.

Management

• Prune dead/diseased branches to healthy wood
• Minimize wounding
• Monitor for wilt/canker progression
• Accept limited lifespan