Basil downy mildew was identified first in Minnesota in 2012. With the right weather conditions basil downy mildew can spread rapidly and result in complete yield loss. The pathogen that causes basil downy mildew (Peronospora belbahrii) is not able to survive MN’s winters. However, it can be reintroduced on infected seed or transplants or by windblown spores.
Michelle Grabowski, Extension Educator of University of Minnesota, has a few bullets explaining how to identify basil downy mildew:
- Infected leaves first turn yellow in areas restricted by major veins, with time the entire leaf turns yellow.
- Irregular black spots appear on infected leaves as they age.
- Fluffy gray spores grow on the underside of infected leaves.
- Infection starts on lower leaves & moves up the plant.
You can see the full post about Basil Downy Mildew here.