Evaluation of Fungicides for Control of Summer Patch

March 15, 2005

Summary: In a replicated field trial at Hacienda Golf Club, La Habra Heights, CA, fungicides were tested at various rates, in various combinations and sequences for control of summer patch on a Poa annua putting green. Key results include:

Heavy disease pressure was observed, with summer patch (Magnaporthe poae) causing the most severe damage. Anthracnose (Colletotrichum graminicola) and Rhizoctonia spp. were also present in test plots, and were responsible for turf damage as well.
The best summer patch control was observed in fungicide rotation programs that used azoxystrobin (Heritage) or azoxystrobin and thiophanate-methyl (Cleary’s 3336) in the latter part of the season, and a sterol inhibitor (tebuconazole or propiconazole) in the early part of the season. In addition to providing very good control of summer patch, anthracnose and Rhizoctonia, these programs have the additional merit of rotating among different classes of fungicides, and thus helping to avoid development of fungicide resistance.
Rotations of Bayleton with Heritage, as well as the experimental product Compass (trifloxystrobin) provided some control of summer patch, but the overall control achieved was not acceptable, with these treatments performing significantly better than the check on only zero to two out of seven rating dates. The combination of Compass plus Banner did not perform any better than Compass alone. This may be due to the fact that the mixture was applied monthly, while the unaccompanied Compass (0.20 oz/1000) was applied bi-weekly.
Tebuconazole (Lynx) not only provided very good control of summer patch and anthracnose in this and other trials, but also was effective in selectively removing Poa annua from bentgrass, without damaging the bentgrass. This feature makes Lynx an interesting option for superintendents who are trying to maintain Poa-free bentgrass greens.
All products provided excellent control of anthracnose, and most products (with the exception of trifloxystrobin) provided excellent control of Rhizoctonia spp.

Printable version of full report

Principal Investigators: Wendy Gelernter, Ph.D. and Larry J. Stowell, Ph.D., CPPP, CPAg

Cooperator: Rafael Barajas, Hacienda Golf Club

Sponsor: Bayer, W.A. Cleary’s, Novartis