| | Index of diseases
J. Drew Smith, P.Ag., Agriculture Canada, Saskatoon, (retired) and I.R. Evans, P.Ag., Alberta Agriculture and Food (retired)
The most damaging effects of turf grass diseases may often be avoided by good cultural practices such as sound turf establishment, correct fertilization, suitable irrigation, timely thatch removal, adequate soil and air drainage, and snowdrift control. The selection of the most suitable turf grass cultivar or mixture of cultivars is of major importance in minimizing the risk of infection and reducing disease damage. However, the cultivars used are not perfectly adapted to a mown turf environment or to the entire range of climatic conditions that may be met in western Canada.
On the west coast the climate is generally mild, wet, and equable. Most of the Prairies are in the western dry region which extends to eastern Manitoba, with hot dry summers, very cold winters, and lighter snowfall than in eastern Canada. East of Manitoba lies the eastern wet region, for the most part with seasonally well distributed, abundant precipitation. Here the summers are more humid and the snowfall heavier than in the Prairies. But within these greater climatic belts, topography may result in localized climates which differ considerably from the average.
The species of turf grasses that can be used and the range of diseases found, are both determined largely by climate. For example, several different bent grass, fescue, and perennial rye grass cultivars are commonly used in domestic lawns on the west coast. Because perennial rye grass will not survive the prairie winter, lawns there are either of Kentucky blue grass alone or in mixture with creeping red fescue. Bent grasses will not survive in domestic lawns or in golf greens without protection from snow moid attacks, low-temperature injury, and desiccation.
Fungicides are often needed to control both summer and winter diseases. In selecting a fungicide, the fungal pathogen(s) must be identified. It is important to know whether more than one fungus is involved, since some fungicides have a narrow and some a wide range of effectiveness. Often, disease is caused by mixtures (complexes) of pathogens, adverse climatic conditions, and physical and chemical characteristics of the soil. Correct diagnosis is therefore very important.
The efficacy of many fungicides against specific turf grass diseases is known from experimental work in Canada and elsewhere. Although some have had extensive practical usage in other countries, only a limited number of chemicals are registered for certain diseases in Canada. With some materials, registration has been denied or withdrawn because of environmental safety considerations.
Fungicides act most effectively if used to prevent disease and should be applied, if possible, as preventatives before disease appears. Curing a disease already present is more difficult, particularly if plant growth is slowed by unfavorable conditions. Some fungicides act systemically, that is, they are taken up by the plant and act upon the fungus from within; nonsystemic fungicides mainly affect the fungus external to the plant. The usual precautions for storage and use of chemicals should be taken with fungicides. Follow the manufacturer's directions on the label.
For most leaf diseases the recommended dosage of an appropriate fungicide should be applied in 10 to 24 litres of water per 1 00 square metres. Where a shoot base or root drench is r equired, double the volume. With some fungicides the margin of safety is small, which emphasizes the need to adhere to the dosage recommended by the manufacturer. Generally, sprays are more effective than dry powder or granular applications.
In Canada, plant protection materials are registered for commercial (C) or domestic (D) use by crop, and disease or pest. Fewer registered turf fungicides are available in Canada than in some other countries. The professional user has a wider range of turf fungicides available than does the domestic lawn owner.
Further information on pests and diseases of lawn grasses:
Index
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