Response of Microbial Populations on the Creeping Bentgrass Phyllosphere to Periodic Fungicide Applications

Fungicides are frequently applied on golf course putting greens to combat the myriad of diseases that can affect them; however, it is unknown how these fungicides may affect microbial populations. Plant-associated microbial communities are intimately involved with plant development and soil biological processes. This two-year study was designed to evaluate the impact of five selected fungicides on culturable actinomycetes, fungi, general bacteria, and fluorescent pseudomonads residing in the turfgrass phyllosphere. Fungicides were applied at label rates on a 14-day interval. Four samples, consisting of five individual turf plants, were taken five days post-application. Samples were homogenized in 1 ml sterile deionized water and serial diluted to 10 −3 and 10 −5 . Each dilution was then plated onto four different media (actinomycete isolation agar, acidified potato dextrose agar, nutrient agar + 1% sucrose, and King’s B) for enumeration of microbial populations. Fungicides had both positive and negative impacts on the culturable microbes tested, although population shifts across all treatments were observed with the prevailing weather conditions. These results show that while response to repeated fungicide application appears to be organism dependent, microbes are not completely removed from the environment.