Pacific Northwest 1998 An Online Guide to Plant Disease Control

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Blueberry -- Bacterial Canker
 
Cause: Pseudomonas syringae pv. syringae, a bacterium that survives and multiplies on the stem surface but causes no damage until it enters the stem. Entry is through wounds, natural openings such as leaf scars, and probably through frost- or winter-injured tissues as well. Two common genetic traits increase the bacteria’s ability to cause disease. Most produce a powerful plant toxin, syringomycin, that destroys plant tissues as bacteria multiply in a wound. Bacteria also produce a protein that acts as an ice nucleus, increasing frost wounds that bacteria easily colonize and expand. ‘Atlantic’, ‘Burlington’, ‘Coville’, ‘Chandler’, ‘Darrow’, ‘N15G’ (‘Eberhardt’), and ‘Patriot’ are susceptible; ‘Elliot’, ‘Rancocas’, and ‘Weymouth’ seem more resistant.
Symptoms: Only canes produced the previous season are attacked. A water-soaked lesion first appears on canes in January or early February and rapidly becomes a reddish brown to black canker. Cankers may extend from a fraction of an inch to the entire length of the 1-year-old cane. Buds in cankers die. If the stem is not girdled, buds above the canker grow. If girdled, the cane portion above the canker dies. Leaves turn orange and wilt if death occurs after buds have leafed out. The disease also will attack cuttings in propagation beds. Severe Botrytis infection can cause similar symptoms.

Infections do not generally go beyond one year old wood.

Bacterial canker can occur on leaves, shoots and flowers.

Sometimes Pseudomonas can cause leaf spots.

 
Cultural control:

  1. Prune out all diseased wood as soon as it is noticed and especially before fall rains.
  2. Avoid late summer nitrogen fertilizer applications.
Chemical control: Spray twice, first before fall rains, preferably the first week in October, and again 4 weeks later. Several spring applications are recommended in British Columbia, starting at budbreak and using the lower rates of copper. Bacteria resistant to copper products have been detected frequently in many ornamental nurseries in the Willamette Valley and blueberry fields in BC.

  1. Bordeaux 8-8-100 plus spreader sticker.
  2. Copper-Count-N at 8 to 10 qt/A. 12-hr reentry.
  3. Cuprofix Ultra 40 Disperss at 3 to 4 lb/A. 12-hr reentry.
  4. Kocide 3000 at 1.75 to 3.5 lb/A. Not for use in the spring. 24-hr reentry.
  5. Nordox 75 WG at 6.5 to 10 lb/A plus spreader sticker. 12-hr reentry.
  6. Nu-Cop 50 DF at 6 lb/A. Not for use in the spring. Nu-Cop 50 WP can be used for organic production. 24-hr reentry.
Biological control:
  1. Serenade MAX at 1 to 3 lb/A. Active ingredient is a protein from Bacillus subtilis strain QST 713. Efficacy in the Pacific North-west is unknown. 4-hr reentry.
References:
Scheck, H.J., J.W. Pscheidt, and L.W. Moore. 1996. Copper and streptomycin resistance in strains of Pseudomonas syringae from Pacific Northwest nurseries. Plant Disease 80:1034-1039.
Content edited by: Jay W. Pscheidt on January 1, 2009
 
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