Garlic mustard is an invasive, exotic herb that is now widespread in North America. Recent research has shown that garlic mustard exudes biochemical compounds that inhibit the growth of entomopathogenic fungi. We investigated how the removal of garlic mustard would affect the abundance of entomopathogenic fungi in forest soils in eastern New York. Using a standard bioassay, we compared the abundance of entomopathogenic fungi in soil with and without garlic mustard both before and 45 d after garlic mustard had been experimentally removed. In soil from which garlic mustard had been experimentally removed 45 d earlier, the abundance of entomopathogenic fungi was restored to levels found in soil with no history of garlic mustard. These results suggest it is possible to increase the abundance of entomopathogenic fungi in the soil in a short time by eradicating garlic mustard plants from an invaded area. Recolonization by entomopathogenic fungi could be beneficial to humans if it increases the mortality of arthropods that are vectors of infectious disease, such as blacklegged ticks, but harmful if it increases the mortality of arthropods that provide valuable ecosystem services, such as bees and ants.
Nomenclature: Garlic mustard, Alliaria petiolata (Bieb.) Cavara & Grande, Beauveria bassiana (Bals.-Criv.) Vuill
Management Implications: Garlic mustard is known to have an inhibitory effect on arbuscular mycorrhizal fungi in the soil. However, less is known about the herb's effects on underground entomopathogenic fungi, or more specifically, about how the soil microbiota responds to the removal of the plant. We investigated how long it takes for the soil to recover natural levels of entomopathogenic fungi once garlic mustard is removed. In this study, we sampled soil for entomopathogenic fungi in areas invaded by garlic mustard and areas free of garlic mustard. We then removed garlic mustard plants from forest plots and sampled the soil again 45 d later. The abundance of entomopathogenic fungi in all areas that had garlic mustard removed from them increased during the 1.5-mo period and reached even greater levels compared with areas which had no history of garlic mustard. Soil disturbance alone did not have an effect on the abundance of entomopathogenic fungi. The ability of entomopathogens to recover shortly after garlic mustard removal can benefit humans because the number of disease-carrying arthropod vectors (e.g., blacklegged ticks) may decline as a result. However, it can also be harmful to us because the number of arthropods that provide valuable ecosystem services (e.g., ants, bees) may also diminish. We conclude that garlic mustard removal might be one of the ways to increase the abundance of entomopathogenic fungi in the soil during a short time and, therefore, a way to restore a natural mechanism for arthropod population control.