You Are Here: Management Updates 2003 Archive September 25, 2003

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Date: September 25, 2003
Category: Diseases
Subject: Dollar Spot, Fungicides, Gray Leaf Spot in NJ

Dollar spot continues to be a major problem for many turfgrass managers. On golf courses, it seems worse because stress is greater: lower mowing heights, the goal of fast greens (i.e. dry and lean- low N), compaction from greater play and less aeration. This means that the disease is more severe when it occurs and that superintendents are more reliant on fungicides to control a disease that could be controlled by cultural practices. In lawns, fungicides are rarely needed. Dollar spot is a sign that the turf needs more water, more N, and/or compaction relief.

Fungicides are very effective for foliar diseases such as dollar spot, but fungicide resistance is more common for dollar spot than for other diseases. Therefore, rotation among chemical groups and protectant fungicides, such as chlorothalonil, is important. New products and old products with new names are becoming available. It is necessary to know the active ingredient name to determine what chemical group a product belongs to. These are listed on the UMass Turf Fungicide Chart (available in the Online Publications section of this web site). Trade names under which active ingredients are sold are listed on the first two pages. The chemical groups to which the active ingredients belong are on the last page.

A new fungicide from a new chemical group, Emerald™, is now available and gives long lasting control of dollar spot. Repeated use will lead to resistance. A label change on Compass™ (trifloxystrobin) indicates that it suppresses, not controls, dollar spot. It must be mixed with a standard dollar spot fungicide for good dollar spot control. The significance of this label change is that Compass™, a strobilurin fungicide, does not enhance dollar spot as Heritage™ (azyoxystrobin) can and actually suppresses it so that it will assist the dollar spot fungicides in controlling this difficult disease.

Gray leaf spot is active in limited areas in the New Jersey area. The warm, moist weather predicted in the coming week could result in disease in perennial ryegrass fairways. In NJ, a lawn was destroyed by gray leaf spot. Lawn care managers who see unusually severe leaf spot activity should have the problem diagnosed. So far, gray leaf spot has been primarily a disease of golf fairways rather than athletic fields and lawns, but we do not know why.

- Submitted by: Dr. Gail Schumann