While it is a long-term goal of the Scandinavian golf sector to minimize pesticide use, one or two fungicide applications against winter diseases can hardly be avoided on putting greens with a turf cover consisting of Agrostis stolonifera or Poa annua. Thus, fungicides used for this purpose should combine a high efficiency against diseases and a low susceptibility to leaching losses. As earlier projects showed iprodione to be susceptible to leaching from USGA greens, the objective of this project was to evaluate three other fungicides used for turf.
The project was carried out at the Bioforsk research stations Landvik (58ºN, 12 m a.s.l.) and Apelsvoll (61ºN, 250 m a.s.l.) in Norway. Two USGA-spec. golf greens; one of them including lysimeters established without organic matter or with 2% (w/w) garden compost (Green Mix) in the rootzone, were sprayed for two consecutive years with prochloraz (450 g a.i./ha), azoxystobin + propiconazole (200 + 125 g a.i./ha), or trifloxystrobin + propiconazole (187.5 +125 g a.i./ha). Iprodione (2250 g a.i./ha) was included outside the lysimeters due to space limitations. As compared to the unsprayed control treatment, none of the fungicides had any effect on Gaumannomyces graminis at the applied rates, but azoxystobin + propiconazole and trifloxystrobin + propiconazole were more efficient than prochloraz and iprodione against controlling Microdochium nivale and Typhula incarnata. Inclusion of organic matter in the rootzone enhanced tiller density and overall turfgrass quality. Traces of prochoraz or trifloxystrobin were never detected in water samples. Traces of propiconazole were also mostly below the environmental safety limit (ESL). By contrast, azoxystrobin was found to exceed the ESL of 0.90 μg/l on four occasions, the highest value being 2.15 μg/l. However, as soil organic matter efficiently prevented leaching, high concentrations were only detected in leachate from straight sand rootzones. Since azoxystrobin + propiconazole and trifloxystrobin + propiconazole had equal effect on winter diseases, the latter should be the preferred choice for preventive fungicide applications in late autumn. Use of azoxystrobin + propiconazole should be limited to greens with organic matter in the rootzone.