P-013 - Evaluating the efficacy of chemical treatments and determining cutting depths for cherry bacterial canker management in young orchards in Washington

Bacterial canker disease (BCD) caused by Pseudomonas syringae pv. syringae and P. amygdali pv. morsprunorum, threatens Washington’s (WA) $800 million cherry industry. A major BCD problem in WA is head cutting infection in newly established orchards in the spring. Copper has long been used for cut-wound protection, but prolonged copper-based treatment has led to widespread resistance. We evaluated the efficacy of lime sulfur (LS), acibenzolar-S-methyl, tetracycline (Tc), latex paint (LP), copper; BadgeX2 (BX2), and kasugamycin (Ksg) in preventing cut-wound infection in newly planted cherry trees. Randomized controlled field experiments with 190 cherry trees were conducted in early and late May, representing hot-dry and cool-humid conditions.  Canker development was monitored at 3, 5, and 8 weeks after pre and post-inoculation treatments. Statistical analysis showed significant differences in canker progression between treatments. Our results showed that Tc exhibited the highest efficacy with shortest canker length (13.83mm) compared to LP+BX2 (32.17mm) in early May. In late May, treatments were less efficient than those of early May, but Tc, Ksg and LS remained the most effective. To assess optimal cutting depths, bacterium was isolated from 1, 1.5, 3, and 5 inches below visible canker and no bacteria were recovered after cutting 5-inches below visible canker. Our findings suggest no current treatments are 100% effective for BCD cut-wound protection. However, chemical application timing, weather conditions, and head cutting time might be crucial in preventing BCD infection.