Effect of Pathogen Isolate, Potato Cultivar, and Antagonist Strain on Potato Scab Severity and Biological Control

Abstract

Antibiotic-producing Streptomyces spp. have shown potential in biocontrol of potato scab caused by Streptomyces scabies. However, results have been inconsistent among field trials. Pathogen isolate, antagonist strain and potato cultivar were investigated as potential sources of variation in the efficacy of potato scab biocontrol. Biocontrol success varied significantly among pathogen isolates and was not correlated with in vitro sensitivity to antibiotic inhibition. Antagonists also varied in their effectiveness as biocontrol agents, and the relative effectiveness of different antagonists varied among growing seasons. Finally, biocontrol varied among potato cultivars in the field. The diverse origins of significant variation in potato scab biocontrol suggest that consistent control in the field is likely to be difficult to achieve.

Keywords:

• biological control
• antagonistic Streptomyces spp
• potato scab
• Streptomyces scabies
• potato cultivar

Acknowledgments

This work was supported by USDA North Central Region Integrated Pest Management Grant 99-EPMP-1-0635, and by a grant from the Minnesota Department of Agriculture. The technical support of Ms. Kyoko Shimizu contributed significantly to the work.