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Effect of Spring-Pruning Method, Copper Sprays and Training Systems on Bacterial Canker of Sweet Cherry 2010

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Project Leaders: Carroll, J. E.; Burr, T. J.; Robinson, T. L.; Hoying, S. A.

Abstract: Activities: Pruning techniques and bactericides (copper, COCS or Cuprofix Ultra at 4 lb/100 gal, phosphorous acid, Agri-Fos at 2.5 qt/100gal, applied in March and April, or no treatment) were evaluated in bacterial canker field experiments in replicate sweet cherry orchard blocks at the NYSAES, Geneva, NY and the Hudson Valley Lab, Highland, NY (2009 only; no bactericides). In 2008, trees were pruned and inoculated in April. In 2009 and 2010, another experiment was conducted with pruning and inoculation in March, April, May and post-harvest. Pruned branches averaged 3.5 cm diameter and cuts left a stub, average 20-cm-long. In 2008, flush cuts were compared to stub cuts in a separate experiment. Cut surfaces were inoculated with copper-sensitive Pseudomonas syringae pv. syringae (Pss) (10 to the 8th cfu/ml). In 2010, the impact of natural and induced freeze events on canker progression was examined. Canker progression was assessed during the growing season. In 2008, bacteria were re-isolated from inoculated cuts and Pss identified with biochemical and PCR assays. In 2008, the efficacy of phosphite or copper against leaf scar infections generated by inoculating branches at 80 percent leaf drop was tested and bud blast assessed. In the 2008-2009 dormant season, six sweet cherry orchard planting systems and five cultivars were assessed visually for incidence of cankers to rate relative susceptibility. Laboratory experiments with detached shoots and green cherry fruit were conducted to determine pre-infection and post-infection activity of labeled or specified rates of copper hydroxide (standard), phosphite, Pentra Bark, kasugamycin, biological MOI-106, biological yeast in proprietary buffer, oxytetracycline, urea, Bacillus subtilis, and hydrogen dioxide against Pss, compared to untreated. The isolate of Pss used for inoculum in the field experiments (Ps34 collected by Burr from sweet cherry, Wayne County, NY) was submitted for genome sequencing. Three naturally-occurring, streptomycin resistant isolates of Pss were recovered from apple buds in Geneva, NY. Events: A 2009 Sweet Cherry Field Meeting and a 2010 Summer Fruit Tour held at NYSAES, Geneva, NY featured our research, reaching over 240 sweet cherry growers, nurserymen, industry personnel, consultants, educators and faculty. Services: We ruled out bacterial canker outbreaks at three orchards and verified bacterial canker at three orchards. Products: Copper and phosphite are essentially ineffective against bacterial infections of pruning cuts, pruning stubs may effectively contain canker infections, and cankers progress least when pruning is done after harvest. Flamout and Kasumin show activity against Pss infection in sweet cherry. We have a collection of contigs for the Ps34 genome and a physical collection of 420 Pss isolates. Dissemination: Carroll provided research results to Cornell Cooperative Extension for summer and winter fruit schools for farmers and presented project results to scientists at the American Phytopathological Society, the Great Lakes Fruit Workers, and the Cumberland-Shenandoah Fruit Workers meetings.