Good to know. How might I have more reasonably reacted?
Cultural control: Bacterial canker is best managed through the use of many different tactics.
1. Plant resistant cultivars and/or rootstocks. For example, F12-1 Mazzard rootstock with scions from virus-tested (and found to be free of all known viruses), canker-free trees has been very useful. Make buds or grafts at least 12 to 15 inches away from the trunk. Mazzard seedling and Gisela 6 rootstocks are also useful.
2. Do not interplant new trees with old trees which are a major source of the bacteria.
3. Locate orchard in an area less likely to be affected by frost. If planting in the spring, plant orchards after frost is likely to occur. Prevent winter injury by painting trunks white and avoiding late season fertility.
4. Test soil for ring nematodes before planting. Also test for pH and other physical characteristics that can be corrected prior to planting.
5. Provide optimal soil conditions for growing cherries including attention to pH and nutrition. Annually monitor for adequate nutrient levels such as nitrogen. Keep irrigation off above ground parts for the first few years.
6. Control weeds.
7. Delay dormant pruning until January or February. Summer pruning should be done after harvest, when weather is dry. Make heading cuts after planting only during dry weather when rain will not occur for at least a week after pruning.
8. Completely remove infected trees or branches girdled and killed by cankers. Do not allow trees to regrow from roots or trunks left after a major trunk canker has been removed.
9. In summer, small cankers may be cut out using the following method. Cut away bark above and around the edges of the infected area. Use sharp tools, and leave wound margins smooth and neat. In nonirrigated orchards, wounds may be left uncovered during summer but should be treated with a wound dressing before fall rains begin. In sprinkler-irrigated orchards wounds may be soaked frequently, so they should be covered with a dressing as soon as possible after cutting. Sterilize all pruning tools between cuts with 10% Clorox (bleach) solution or shellac thinner (70% ethyl alcohol).
10. Cauterizing cankers using a hand-held propane burner has been used with some success in New Zealand.
11. Scoring tree trunks has been practiced by Willamette Valley growers for several years. Grower testimonials point to some benefits but there has been no research on this possible efficacy of the practice. A sharp pocket knife is used to make a vertical shallow cut in the tree trunk. The resulting wound tissue that develops is supposed to resist canker development and prevent trunk girdling. Knives should be disinfected between trees.
Chemical control: Copper-based products have not worked well under conditions favorable for disease development. Bacteria resistant to copper products have been detected throughout our cherry growing regions, which compromises chemical control tactics. In small plot disease control trials it is not unusual to find copper treated trees with more disease than trees without any treatment. Heavy use of copper products is not recommended as concentrations in the soil can build up to toxic levels after several decades of use.
Focus on cultural control tactics first and supplement with chemical control. Traditional recommendations encourage the first spray to occur in October before fall rains, followed by another application in early January. Growers should consider adjusting the timing of sprays to coincide with leaf fall. Thorough coverage is needed. Protecting heading cuts made after planting a new orchard is also important. Protect both orchard and nursery trees (sweet cherry, prune, and plum). Some growers use low rates of copper-based products during bud break to reduce symptoms of dead bud.
1. Bordeaux 12-12-100.
2. Champ WG at 8 to 16 lb /A. Champion WP can be used for organic production. 24-hr reentry.
3. C-O-C-S WDG at 8 to 12 lb/A plus dormant spray oil. 24-hr reentry.
4. Copper-Count-N at 6 quarts/100 gal water. Use only 2 to 3 quarts/100 gal water during bloom. 12-hr reentry.
5. Cueva at 0.5 to 2 gal/100 gal water/A. 4-hr reentry.
6. Cuprofix Ultra 40 Disperss at 5 to 8 lb/A. 48-hr reentry.
7. Kocide 3000 at 3.5 to 7 lb/A plus 1 pint superior-type oil/100 gal water. 48-hr reentry.
8. Nordox 75 WG at 5 to 13 lb/A. 12-hr reentry.
9. Nu-Cop 50 DF at 8 to 12 lb/A. Nu-Cop WP can be used for organic production. 24-hr reentry.
Kennelly, M. M., Cazorla, F. M., de Vicente, A., Ramos, C. and Sundin, G. W. 2007. Pseudomonas syringae Diseases of Fruit Trees: Progress Toward Understanding and Control. Plant Disease 91:4-17.