Sensitivity of Sclerotinia homoeocarpa isolates from turfgrass in Italy to demethylation-inhibiting (DMI) fungicides and iprodione

Sclerotinia homoeocarpa F.T. Bennett is one of the most important pathogens affecting high maintenance turfgrass in Italy. Control of this pathogen still relies on the use of fungicides. Twenty nine isolates of S. homoeocarpa collected from 13 different golf courses in northern and central Italy were tested in vitro for their sensitivity to propiconazole, tebuconazole and iprodione, fungicides registered for use on turfgrass in Italy. Three isolates from untreated turfgrasses were use as reference isolates. The tests were carried out on an agar medium amended with 0, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, 100, 300 µg mL–1 of the active ingredient of each fungicide. Most of the isolates showed reduced sensitivity to the tested fungicides, while maintaining their virulence when inoculated on potted Agrostis stolonifera L. Fungicide resistance in this pathogen has increased in Italy compared with the situation 10 years previously