As if this summer’s drought conditions in Maine were not hard enough on lawns, recent rain and humidity have created the perfect conditions for a fungal disease that’s not been seen in the state for at least three decades. The fungus is turning those lawns a startling shade of black and has homeowners calling plant experts looking for solutions.
Unfortunately, there are none.
In the last week alone plant experts at University of Maine Cooperative Extension have received dozens of calls from homeowners wondering why their lawns were suddenly becoming patchworks of black and green.
“We are seeing this across the entire state,” said Dr. Alicyn Smart, plant pathologist with Cooperative Extension. “I’ve never seen it before, and a landscaper told me it’s the first time in 30 years he has ever seen it, and some landscapers in the state report not encountering it at all throughout their careers.”
What people are seeing are the black spores of the pathogen Cladosporium creating a condition known as black lawn. And according to Smart, any part of a lawn that the spores turned black was an area already in trouble.
“It’s a parasitic fungus that takes advantage of dying tissue,” she said. “A lot of lawns around Maine were dying or already dead due to being stressed by the drought conditions and this opportunistic fungus took advantage of that.”
And just because few people have ever actually seen black lawn disease in Maine does not mean it hasn’t been here all along just waiting for the right conditions to multiply and spread, Smart said. The drought, combined with recent humidity and reains created those perfect conditions.
“The spores are always present but we just don’t see them,” Smart said. “There are really a lot of pathogens like that.”
The spores of Cladosporium are dispersed by the wind or on water droplets which Smart said making them a very efficient traveler.
Because the black grass is already dead, the only solution to having a green lawn again is reseeding it once the drought conditions are over. Since the fungus is the result of an environmental issue, Smart said there is no purpose to applying a chemical fungicide.
The only way to prevent it in the first place is to keep the lawn’s environment stable with the proper amount of moisture to prevent it from drying up and dying off.
“It does not have to happen,” Smart said. “You can water your lawn so it does not get stressed out but you do need to consider your water levels in your well and that is a personal call.”
The good news is other than being somewhat unsightly, the fungus is not dangerous to humans, pets or vegetable and flower gardens in Maine, Smart said.
The cooperative extension has published an online black lawn resource page that can be accessed by going to www.extension.umaine.edu and selecting “Insect Pests, Plant Diseases & Pesticide Safety.”