Bacterial blight caused by Pseudomonas marginalis is a minor disease of parsnip that occurs wherever parsnip is grown.
Initial symptoms of bacterial blight include a firm rot of parsnip petioles with associated browning of vascular tissue in both the crown and the root. Brown, sunken lesions develop on petiloes, crown, and root.
P. marginalis survives in infested crop residues and enters the plant through natural openings or wounds during periods of extended leaf wetness. The bacteria are disseminated by water splash from infected residues, the soil, or adjacent diseased plants.
Severe infections can cause complete collapse of petioles and make mechanical harvesting difficult. P. marginalis can cause soft rot in storage.
Cultural Controls & Prevention:
- Control measures are usually not warranted.
- Provide good drainage as the disease is most severe in low areas where water stands.
- Avoid wounding crowns and petioles.
- Crop rotation promotes complete decomposition of parsnip residues and reduces carryover of inoculum in the soil.
Chemical Controls & Pesticides:
For Current information on disease recommendations ins specific crops including information on chemical control & pesticide management, please visit the New England Vegetable Management Guide website.