Fungi exist all around us; most of them we never even see. Considering all the different fungi, very few cause turfgrass diseases. Even the most aggressive fungal pathogens require the right circumstances before they can overcome turfgrass defenses and cause disease symptoms. Often, disease-causing fungi are suppressed by beneficial fungi before they cause problems. Beneficial fungi can hinder pathogenic fungi via exclusion or, in some cases, by producing antagonistic natural chemicals that suppress disease-causing fungi.
Fungicides in the strobilurin class were discovered and synthesized by studying natural chemicals produced by wood-decaying fungi that are damaging to other fungi. Similarly, species of Ceratobasidium – a genus of fungi closely related to Rhizoctonia – can compete with and exclude pathogenic fungi like Rhizoctonia solani, the causal agent of brown patch or large patch. Orchid roots are even intentionally inoculated with Ceratobasidium, acting almost like an immunization against disease-causing fungi. Trichoderma is another commonly occurring genus of fungi that areused as a biological control or suppressant of other fungi.
Some fungi are also considered delicacies. Elm, ash and pecan trees often host mushrooms prized by gourmet chefs. Truffles and morels are the fruiting bodies of fungi that tend to be mycorrhizal in nature, growing in association with trees. Some truffles are known as black gold for good reason, as 1 pound of truffles can command prices of $300 to $500 a pound.
So, before you crank up the sprayer, think twice about fungicides and why you are spraying them. You may be hurting beneficial fungi that are helping exclude the pathogenic ones.
Southeast Region Agronomists:
Chris Hartwiger, director, USGA Course Consulting Service - firstname.lastname@example.org
Steve Kammerer, regional director – email@example.com
Patrick M. O’Brien, agronomist – firstname.lastname@example.org
Todd Lowe, agronomist – email@example.com