Cool season turf degree control
1 Sep, 2008 By: Henry Wilkinson Landscape ManagementThe nights are finally cooler and the grass is growing again. It's time to refresh your plant pathology knowledge. You don't want to get caught by a tough disease — or an even tougher customer unhappy about a diseased lawn.
 Gray leaf spot becomes a problem when the weather is hot and humid. |
The key to good turf management (not to mention retaining lawn care customers) is to sustain a consistent quality. This means having a management program that discourages problems like disease.
History as your guide
Perennial patch diseases include take-all patch, summer patch, necrotic ring spot and zoysia patch. If you had these diseases last year, you will very likely have them this year as well. All of these diseases start their yearly development when the soil temperature (at 1-in. soil depth) is about 65°F to 70°F and the soil is moist (irrigation or rain). This is right about now for most readers. However, this is not when you or your customer will see the disease:
- Take-all patch starts about May, and you will it in June.
- Summer patch starts in May, but you may not see it until July, August or September.
- Necrotic ring spot starts in May, but you will see it in September.
- Zoysia patch starts in November and becomes visible in April and May.
Lethal leaf diseases include Pythium blight and gray leaf spot (GLS). If you had either of these diseases last year, you know that they can kill turf. Will they occur this year? That is mainly dependent on the prevailing weather conditions and health of your turf in July, August and September.
 Fairy rings are often more unsightly than damaging. |
Pythium will attack turf that is rich in nitrogen, when the weather is very humid, calm and hot. Until those conditions develop, you can relax — but keep your eye on the weather.
GLS is mainly a problem on ryegrass. If you have ryegrass, you can relax until the weather in late August and September becomes very hot and humid. Be vigilant: GLS is fast and furious once it starts.
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