- Fruits: apples, pears, general tree fruits
- Education and Training: demonstration, on-farm/ranch research
- Farm Business Management: agritourism
- Pest Management: biological control, biorational pesticides, chemical control, cultural control, field monitoring/scouting, prevention, sanitation
- Production Systems: general crop production
In 2008 and 2009, severe fire blight (Erwinia amylovora) occurred in Illinois apple orchards, leading to speculation that streptomycin-resistant strains of E. amylovora might be present in some orchards. Statewide surveys were conducted in 2010, 2011, and 2012, and 117, 129, and 170, E. amylovora isolates were collected, respectively, from 20 counties. None of the 416 E. amylovora isolates tested were resistant to streptomycin (Agri-Mycin 17WP) at 50 mg/liter. Seven non-E. amylovora bacterial isolates were collected from E. amylovora-infected shoots that contained both a strA-strB streptomycin-resistance gene and IS1133 on transposon Tn5393, which could be a potential source of streptomycin-resistance for E. amylovora in Illinois in the future. Colony development of all 84 E. amylovora isolates tested was inhibited on LB medium amended with oxytetracycline at 50 mg/L and kasugamycin (Kasumin 2L) at 100 mg/L. Similarly, colony development of the 84 E. amylovora isolates was inhibited on CYE medium amended with copper sulfate at 0.16 mM. In 2011 and 2012, field trials were conducted to evaluate efficacy of oxytetracycline (Mycoshield 17WP), kasugamycin (Kasumin 2L and ARY-0416-06), copper hydroxide (Kocide-3000 41.6DF), Bacillus subtilis (Serenade Max, QST713), and Pseudomonas fluorescens (Blight Ban A506) for management of fire blight in an apple orchard. Only kasugamycin (Kasumin 2L and ARY-4016-06) reduced blossom infection significantly. There was a significant interaction of kasugamycin (Kasumin 2L) with prohexadione calcium (Apogee 27.5DF) in reducing shoot blight incidence in the field in 2012.
More than 300 growers manage approximately 5,000 acres of apple orchards in Illinois. Illinois with a population of 13,000,000 is a huge market for apples, particularly for the rapidly growing “You Pick” operations. 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 apple and other pome fruits. However, streptomycin-resistant (SmR) E. amylovora populations have been reported from several apple growing states. Widespread and severe fire blight occurred in Illinois apple orchards in the past five years leading to speculation that SmR strains of E. amylovora may have developed in some orchards in the state. No previous study has been conducted in Illinois to determine the presence of SmR bacterium in the state. Since, streptomycin is the most effective antibiotic for control of fire blight of apple, it is necessary to identify cases of antibiotic-resistance early, before resistant strains become widely established. 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.
Project objectives:div style="margin-left:1em;">
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.