Development of an Integrative Two-tiered Systemic Approach to Manage Bacterial Canker of Sweet Cherry by Targeting Critical Environmental Infectious Periods

View the project final report

Commodities

• Fruits: cherries, general tree fruits

Practices

• Crop Production: application rate management, biological inoculants
• Education and Training: on-farm/ranch research
• Pest Management: biological control, cultural control
• Production Systems: general crop production
• Sustainable Communities: sustainability measures

Pseudomonas syringae pv. syringae (PSS) causes bacterial canker in sweet cherry (Prunus avium L.) resulting in severe crop reductions, loss of fruiting limbs, and even tree mortality. Environmental conditions strongly influence bacterial canker populations and infectiousness, making it difficult to get repeatable results when testing potential control measures in the field. Fundamental work is required to discover the parameters that contribute to infection event success and to develop testing protocols that will assure repeatable results. One of the prerequisites to infection is a susceptible tree compromised by a wound event. Two key infection points for bacterial canker occur 1) during leaf drop (senescence) in which the leaf scars are entry points, and 2) during pruning in the spring. Proposed work includes experiments under controlled conditions to characterize the effects of temperature, free moisture, and inoculum load on plant infection and to create a repeatable infection system that will enable rapid testing of potential control measures with consistent results. The goal of the project is to achieve 100% infection under inoculated conditions and 0% without inoculation. Efficacy of control measures will be evaluated by the reduction of infection from the inoculated controls. Ultimately, the outcomes of these tests will be transferred to field tests of potential control measures in a grower orchard. This work will enable us to instruct growers on when the environment will be most conducive to infection, and allow them to accordingly time sprays and/or other control measures to reduce pesticide use. Potential control measures include pruning at times when the bacterial population is low, and spraying antibiotics or bio-controls only at points when the population might grow. Only copper sprays are available for control of bacterial canker and copper resistant PSS have been documented in Michigan. Continued use of copper sprays will select for the resistance, reducing copper’s efficacy in the future. This work will allow for selected use of spray products, reducing selective pressure for resistance and also save time and money for growers. Infection of pruning wounds will be tested in the field and the effectiveness of biocontrols and pruning timing evaluated. The development of alternative or supplemental control measures to chemical antibiotics and the identification of the environmental and horticultural conditions for their effective application, will improve and expand sustainable sweet cherry production in the Midwest, and increase the availability of regionally-produced cherries for consumer markets in the region.

Objective one: To develop a rapid repeatable infection system for leaf scar and pruning infections which will allow for rapid testing of new potential controls.

Objective two: To help determine the conditions that make sweet cherry more susceptible to bacterial canker infection to allow growers to try to prune when trees are less susceptible or spray to reduce leaf scar infection at key infectious periods.

Objective three: Test hypothesis from previous pruning experiments in the field to test pruning timing and effectiveness of a biocontrol at reducing infection.