Parsley (Petroselinum crispum)-Bacterial Leaf Spot

Cause The bacterium, Pseudomonas syringae pv. coriandricola, is common; Xanthomonas campestris pv. coriandri and X. hortorum pv. carotae also have been reported. Although Pseudomonas sp. has been severe on cilantro in the Willamette Valley of Oregon, the problem occurs much less on parsley.

Symptoms Leaves, petioles, and shoots develop brown necrotic lesions that look water soaked. Severely infected plants may be stunted and yellowed. Flowers also may be attacked and show similar symptoms. Seed decay can also occur.

Cultural control

  • Plant seed under optimal conditions for quick emergence and vigorous growth.
  • Plant seed that is certified to be free of pathogenic bacteria or treat seed with hot water (122°F) for 30 minutes to kill bacteria.
  • Use sterile soil or potting mix to start seeds. Also disinfect any tools and equipment that might be used and contaminate the media.
  • Avoid reusing pots or trays from a previous crop for propagation. If pots must be reused, then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min.

Chemical control

  • Copper formulations (Group M1) are registered for use.
    • Badge SC at 1.25 to 2.8 pints/A on 10-day intervals. Preharvest interval is 0 days. 24-hr reentry for greenhouse use; 48-hr reentry for all other applications.
    • Cueva at 0.5 to 2 gal/100 gal water on 7- to 10-day intervals. May be applied on the day of harvest. 4-hr reentry. O
    • Cuprofix Ultra 40 Disperss on 10-day intervals at 2 lb/A. 48-hr reentry.
    • Kocide 2000 at 1.5 to 2.25 lb/A or Kocide 3000 at 0.75 to 1.75 lb/A on 5- to 7-day intervals. 48-hr reentry.

Biological control

  • Double Nickel LC at 0.5 to 6 quarts/A on a 3- to 10-day interval. 4-hr reentry. O

References Taylor, J.D. and Dudley, C.L. 1980. Bacterial disease of coriander. Plant Pathology 29:117-121.

UMass Extension. Hot water treatment of seeds. At https://ag.umass.edu/vegetable/news/hot-water-treatment-of-seeds (accessed 20 Dec 2017).