Fungus gnats are vectors of pythium.
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Plant pathogenic fungi are one of the most common causes of root impairment in ornamental crops. Accurately diagnosing what pathogen has invaded your plants is paramount in both managing the problem and preventing future incursions.

Pythium is a classic “root nibbler” that can kill plants outright, says Mary Hausbeck, a professor of plant, soil and microbial sciences at Michigan State University.

Like pythium, phytophthora favors excess moisture and nitrogen fertility.

“I’ve never witnessed a situation with phytophthora that was not highly destructive,” Hausbeck says. “A grower may see a problem they think is pythium, but it’s not responding to treatment how they thought it would. That’s when we find out it’s phytophthora.”