Fire blight, caused by the bacterium Erwinia amylovora, is a devastating bacterial disease of apples in Ohio (OH). Fire blight is a systemic disease and one of the most difficult diseases of apple to manage. Current management strategies to minimize production losses include cultural practices and the use of antibiotics. Antibiotics, including streptomycin, oxytetracycline, and kasugamycin, are highly effective in reducing E. amylovora populations during bloom, but continuous use of them is not sustainable. For example, resistance to the most effective of the three antibiotics-streptomycin, has been reported in many orchards in the northeastern United States (US). In addition, the use of antibiotics in agricultural has raised legitimate concerns about the future effectiveness of antibiotics to control human diseases through the transfer of antimicrobial resistance genes to human pathogens.
Biological plant disease control can be integrated into fire blight management programs; reducing or eliminating the reliance on antibiotics. Previous studies conducted in northeastern US states have demonstrated that pairing species of Bacillus with antibiotics can minimize fire blight incidence. Currently, the use of biological control agents (BCAs) to manage fire blight is mostly limited to organic producers and backyard gardeners. Commercial and conventional apple producers have shied away from BCAs for fire blight control because of the lack of consistent efficacy data, the number of applications required to achieve a high level of efficacy, and their short shelf life. Despite these challenges, there continues to be an interest in BCAs for disease management, which probably reflects continued consumer concerns about pesticide use and environmental and human health. However, the identification and implementation of microorganisms with biocontrol activity is slow and requires extensive laboratory and field testing before BCAs make it to the market. In this study, we will evaluate the suppression of E. amylovora isolates with newly identified and novel antagonistic microorganisms. The proposed study aims to characterize and evaluate the efficacy of these novel BCAs for biological control of fire blight in Ohio with the long-term goal of providing sustainable alternatives to antibiotics. Laboratory and field studies to evaluate the efficacy of novel BCAs will be conducted. Field days and grower meetings and conferences, will facilitate apple farmers involvement in the learning process and understanding of the use of BCAs as a sustainable alternative to antibiotics.
Project objectives from proposal:
Outcomes of this project will directly benefit apple growers in OH who have continuous losses due to fire blight disease and use antibiotics as the main strategy to combat the disease.
Learning outcomes: We expect to: 1) identify effective BCAs programs to reduce fire blight incidence and spread in the orchard and 2) increase grower awareness of integrating BCAs into a fire blight management program.
Action outcomes: Apple growers will 1) adopt an effective management approach that can include the use of biocontrol agents to manage fire blight and; 2) reduce their dependency on antibiotics (e.g. streptomycin) use for fire blight management.