Basil downy mildew is back in Maryland gardens

Hurry up and enjoy your basil plants while they are healthy. That insidious disease, downy mildew, is infecting basil across the mid-Atlantic region. I first noticed it in a Howard Co. community garden last week and then in my home garden on July 15th.

Caption: Early, subtle symptoms

Early, subtle symptoms

The initial symptom is splotchy light yellowing of leaf topsides. Those areas eventually turn brown and die. Leaf undersides develop a fuzzy grayish fungal mat with spore structures that appear as tiny dark specks.

Sporulation

Sporulation on leaf undersides

The disease spreads rapidly. You can cut back infected plants to encourage new growth but the young leaves quickly become infected. Planting multiple times in different locations can be a useful strategy. Once plants are infected it’s best to pull them out, harvest usable leaves, and trash the rest of the plant.

The good news is that a Rutgers University team developed four new resistant cultivars available to commercial growers this season. Hopefully, there will be plenty of seed harvested this year so that we can all enjoy the benefits of these new releases.

 

By Jon Traunfeld, Extension Specialist

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