Answer: Red thread doesn't generally kill grass. It is a foliar blight. While it can make the grass look bad, the lawn will nearly always recover when growing conditions improve.
Most active during cool wet weather on slow growing grasses, red thread thrives in a low nitrogen environment and in cool temperatures. It also shows up at times in summer on lawns that are under mild drought stress and or low nitrogen fertility.
The disease can affect most grasses, but is definitely worse on perennial ryegrass, red fescue and chewings fescue. It will also attack old lawns that have a high percentage of bentgrass.
Good lawn care techniques, rather than fungicides, are the key to keeping red thread in control. Here are some steps to follow to get your turf back in shape:
Maintain lawn vigor by fertilizing regularly with a nitrogen-based fertilizer. This is particularly important in spring and fall when red thread is most active.
Use a mulching, rotary lawnmower to return clippings, thus returning nutrients to your lawn.
Dethatch your lawn each spring if it needs it. This allows new grass roots to come into contact with the soil, rather than thatch, and promotes vigorous grass.
Water your lawn some during the summer months.
Fungicides are a last resort in dealing with red thread. Since it is almost impossible to predict when conditions will be just right for red thread, you generally end up treating it after damage is already done. The fungicides that really do a good job on red thread are not easy for homeowners to obtain.
Putting your lawn on a regular feeding, mowing and watering schedule will help control red thread.
Best wishes with your lawn.
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