Wilt diseases: bacterial vs fungal ID

Wilt diseases share a common mechanism: the plant's vascular system is blocked, preventing water from reaching leaves. But the agents behind vascular wilts are very different -- bacterial pathogens, fungal pathogens, and even the physical action of insects -- and the management implications differ.

Wilt diseases share a common mechanism: the plant's vascular system is blocked, preventing water from reaching leaves. But the agents behind vascular wilts are very different — bacterial pathogens, fungal pathogens, and even the physical action of insects — and the management implications differ accordingly. Bacterial wilts have no cure and may require the removal of all host plants in the area. Verticillium wilt kills some plants but many trees survive with good care.

Vascular discoloration: the diagnostic cut

Per Penn State Extension, the confirming test for any vascular wilt:

1. Cut across a symptomatic stem at 4–6 inches above the soil line
2. Look at the cross-section under good light
3. Healthy plant: Vascular ring (xylem) is white to creamy
4. Wilt disease: Vascular ring shows brown, olive-green, or black discoloration — partial ring (one-sided) in Verticillium; full ring in more advanced fungal disease; often streaks along the wood in bacterial wilt