Monthly Spotlight: Leafspot Part 1

Monthly Spotlight: Leafspot Part 1

Ah yes, February. It’s starting to warm up and we’re looking forward to the joys of spring. Unfortunately with the rising temperatures leafspot season is coming. A lot of plant pathogens start becoming active when temperatures get between 50 and 70 degrees Fahrenheit. They thrive in high humidity situations that come with near constant spring rain here in Washington.

This month I’ll be talking about fungal leafspot.

As you might expect, fungal leafspot is the most common of the two seen in landscape plants. Still, when deciding control steps it’s important to identify the type first. When considering fungal infections look for what’s known as the bullseye.

Fungus spread by hyphae, small filamentous fungal root-like structures. There will be a site of infection, for leafspot it’s usually a stomata on the underside of the leaf but it may also be via direct epidermis penetration.

From there the hyphae spread outward killing then eating plant tissue. The bull’s eye shows the stages of infection as the hyphae spread. Often drying out in the middle when the fungi has extracted what it can.

Once you’ve identified a fungal issue it’s important to remember that curative solutions are difficult. If you must treat, treat early and rotate your chemical, look for different modes of action. If you know that a certain crop often has fungal leafspot disease, spray preventatively, it’ll save you time and energy in the long run.

The good news is most plants recover fairly quickly from cold damage and a few quick prunes in spring prior to flush will help with aesthetics and reduce disease concerns.