Fungus-farming termites can protect their crop by confining weeds with fungistatic soil boluses.

The symbiotic agriculture of fungus-farming termites can collapse if they fail to prevent invading weeds. Previous studies suggest a role for symbiotic fungistatic microbes in bringing about weed control. However, how termites employ these microbes to suppress fungal weeds without affecting the fungal cultivar remains unknown. We show that the fungus-farming termite Odontotermes obesus uses specific behaviors to remove, isolate, and suppress the growth of the fungal weed Pseudoxylaria, primarily by encasing it with soil boluses containing fungistatic microbes. These behaviors efficiently suppress the weed without affecting the crop. This integration of specific behaviors with termite-derived microbes appears to be the proximate mechanism of how microbes are topically used by termites to confine the weed while keeping the crop unaffected. Editor's summary: Like leafcutter ants, fungus-farming termites (Odontotermes obesus) form a symbiotic relationship with a fungus (Termitomyces) that serves as a stable food source. An unknown feature of this relationship is how the termites prevent the nutritional "combs" they produce from being overtaken by other fungi such as filamentous Pseudoxylaria, which have been observed to overtake combs when termites are experimentally removed. Panchal et al. observed termites removing Pseudoxylaria and covering them with soil boluses, and fully encasing Pseudoxylaria successfully prevented its infection of combs (see the Perspective by Goes and Adams). Further experiments showed that soil boluses are effective because of the fungistatic properties of bacteria associated with the termites, which the termites selectively apply to the "weedy," but not the crop, fungus. —Bianca Lopez [ABSTRACT FROM AUTHOR]