Basil Downy Mildew Developing on Resistant VarietiesMeg McGrath
August 7, 2021
Meg McGrath, Long Island Horticultural Research & Extension Center, firstname.lastname@example.org:
A few growers have reported this season seeing downy mildew starting to develop earlier on resistant basil varieties and becoming more severe than in the past. The varieties are Rutgers Devotion DMR, Rutgers Obsession DMR, and Prospera. This suggests the pathogen has evolved to overcome resistance in these varieties. A new pathogen race able to overcome resistance in Prospera had already been detected elsewhere (Israel). Please contact me if you see more symptoms than expected on these, the other Rutgers DMR varieties, Amazel, or Pesto Besto. It is very valuable to know how widely this is occurring, and a sample may be wanted for research. The pathogen from affected resistant varieties is being examined to identify how it differs genetically from isolates of the pathogen examined in the past.
See basil downy mildew webpage for information about conventional and organic fungicides. Greatest success will be achieved with a preventive application schedule.