Effective Management for Fire Blight for Sustainable Apple Production in Illinois

Effective Management for Fire Blight for Sustainable Apple Production in Illinois

Summary

Illinois apple growers produce 39.6 million pounds of apples annually. Fire blight, caused by the bacterium Erwinia amylovora, is a serious threat to apple production in Illinois and other Midwestern states. Apple trees are most vulnerable to fire blight infection at bloom. Streptomycin has been the most effective chemical for control of fire blight of pome fruits in Illinois, as well as nationwide. In 2008 and 2009, severe fire blight occurred in Illinois apple orchards, leading to speculation that streptomycin-resistant strains of E. amylovora might have developed in some orchards. State-wide surveys were conducted in 2010, 2011, and 2012, resulting in the collection of 117, 129, and 170, E. amylovora isolates, respectively, from 19 counties. Of the total 416 isolates examined 0 were determined to be streptomycin-resistant at 50 mg/L.

Objectives/Performance Targets

The main goal of this research is to determine if streptomycin-resistant E. amylovora exist in Illinois and develop alternative control measures for the pathogen. The specific objectives of this study will be to: (i) evaluate Illinois E. amylovora populations for streptomycin resistance, and (ii) evaluate streptomycin alternatives, including kasugamycin, oxytetracyline, copper compounds, and bio-control agents for management of fire blight.

Accomplishments/Milestones

Intensive orchard surveys during 2010, 2011, and 2012 showed that Illinois isolates of the bacterium Erwinia amylovora (causal agent of fire blight of pome fruit) are not resistant to the bactericide streptomycin. This is a significant finding and a huge accomplishment.

Impacts and Contributions/Outcomes

The results of this study showed that isolates of Erwinia amylovora in Illinois are sensitive to the main antibiotic, streptomycin. Thus, failure in effective management of fire blight of pome fruit in Illinois is due to growers’ failure in timely applications of control measures. The necessary procedures for management of fire blight of apple have been provided to the fruit growers.

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