You Are Here: Management Updates 1998 Archive July 16, 1998

Date: July 16, 1998
Category: Diseases
Subject: Summer Stress on Turf, Patch Diseases

Last week, many foliar diseases were still active because of continuing rain. These are relatively easy diseases to control with fungicides applied to leaves. Depending on nitrogen status and stress factors, some turf had leaf spot, Leptosphaerulina blight (minor), anthracnose or brown patch.

Over the weekend, mild but dry weather seems to have set up turf in many areas for stress. This is particularly obvious in golf course fairways and some greens where the plants are growing on very compacted, wet soils. Some of these soils continue to have the strong smell of anaerobic conditions. On many golf courses, superintendents were still trying to dry out some of these areas. Unfortunately, the plants growing on top have no where for their roots to grow except in a thin layer near the surface where they are exposed to various stresses including drought and wear. Poa annua plants in particular are showing stress symptoms. Some Poa has Pythium root rot deeper in the wet soil and summer patch is moving into the stressed shallow roots. It is difficult to determine if stress or summer patch or both are contributing to the Poa decline without a microscope. However, if the shallow roots are brown and decayed looking, it is unlikely that any fungicide will offer significant improvement. It's probably better to overseed and aerate in the fall. Routine aeration of these compacted areas is a necessity to avoid these middle of the summer stress conditions. Syringing may help the plants survive the heat. If summer patch is diagnosed and the roots are not too badly diseased,only thiophanate-methyl and azoxystrobin give curative control.

In lawns, similar stresses are resulting in patch disease symptoms. Again, curative chemical control is difficult. Mid-day stress relief with light watering in addition to standard irrigation may help plants survive until the heat breaks and damaged areas can be overseeded.

- Submitted by: Dr. Gail Schumann