TURF TIP
5/14/03

Early Season Dollar Spot Control Makes Sense

The dollar spot pathogen is becoming active or is just around the corner in most of Indiana. The excess rain has caused excess growth and infrequent mowing, which in turn forced clipping removal and removal of N from the system. The N in the system may have been further depleted with the excess rain leaching soil N. This combination sets up an ideal environment for dollar spot, which is most severe on N-deficient turf. The standard May fertilization of 0.75-1.0 lb N/1000 sq. ft. with primarily slow release N should help to minimize these diseases now. On golf courses with a long history of dollar spot, first and foremost review the fertilization practices and increase the annual N if possible. Other cultural practices to reduce dollar spot include early morning rolling, syringing and/or mowing to minimize free water on the leaf surfaces. It makes sense to use fungicides early in the season at the first sign of infection, rather than waiting for symptoms to become obvious. Though this seems to conflict with typical IPM strategy to apply only after symptoms approach an intolerable threshold, we feel early applications will reduce inoculum, thus reducing disease pressure and fungicide use over the whole season. If you choose to apply early (or whenever you apply fungicides for that matter), be sure to rotate fungicides and to tankmix systemics with contact fungicides to help minimize the chances for resistance. Though dollar spot is still maybe a month away on homelawns, the most effective dollar spot control is to increase the annual nitrogen (best applied in the fall). Dollar spot appears to be most common on perennial ryegrass, so avoid more than 10% perennial ryegrass in a seed mix when seeding a new turf area. Fungicidal control is generally not recommended on home lawns.

Rick Latin, Turfgrass Pathologist
Zac Reicher, Associate Professor/Turfgrass Extension Specialist

Send corrections, suggestions, and comments to biehlj@purdue.edu