Back to top

Carrot & Parsnip, Bacterial Blight

Root infection of parsnip by P. marginalis. Photo: R. L. Wick

Pseudomonas marginalis

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.

Life Cycle:

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.

Crop Injury:

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.

Crops that are affected by this disease:

Last Updated: 
January 2013

The Center for Agriculture, Food and the Environment and UMass Extension are equal opportunity providers and employers, United States Department of Agriculture cooperating. Contact your local Extension office for information on disability accommodations. Contact the State Center Director’s Office if you have concerns related to discrimination, 413-545-4800 or see