The Low Down on Leaf Disease
Identifying & Managing the Most Common Leaf Diseases
If you have been consistently watering and fertilizing your lawn, but it still appears yellowish or brown, it could be suffering from one of several common leaf diseases.
What Causes Leaf Disease?
Three factors must be present for leaf disease to occur. A plant (in this case the grass blades), a pathogen (the fungi itself), and the environmental conditions favorable for the disease (wet or humid weather). If any of these are missing, disease will likely not be present. Some of the most common causes of leaf disease include the following:
- Extended periods of humid weather
- Watering at night or significant evening rainfall
- Mowing when the lawn is wet
- Mowing with a dull mower blade
- Cutting the lawn too short
- Nitrogen deficiency
What Are the Most Common Leaf Diseases?
1. Leaf Spot
Leaf spot is identified by small circles of yellow with a dark border. These lesions will appear all over the leaf blade. This disease can be a problem when the weather is warm and humid. Leaf spot often occurs in lawns that are mowed too short.
2. Dollar Spot
Dollar spot is a disease that can occur in lawns during warm, humid weather. The fungus enters the grass plants when they are wet. Large, tan colored wounds appear in an hourglass shape in the middle of the blade. These infected grass blades form rounded damaged patches the size of a silver dollar. Over time, the patches will start to overlap each other causing large dead patches.
3. Leaf Blight
Leaf blight occurs on lawns during hot, humid weather. The disease enters the grass plants after evening mowing followed by excessive night watering. In heavily infested patches, the fungus damages the lawn in circular patches that often form large bleached areas. Closer inspection of the plant reveals individual leaves dying from the tips down with a brownish purple line running horizontal across the plant.
How to Manage Leaf Disease
It’s important to remember that leaf disease is like us having a cold. There isn’t a cure and most strategies work to reduce symptoms. Similar to preventing a cold, you want to make sure your lawn’s “immune system” is strong so that it is less susceptible to disease.
If your lawn is suffering from leaf disease, the best thing you can do is to try and change the environmental conditions. Here are some strategies to do so:
- Avoid evening watering
- Avoid evening mowing
- Maintain a mowing height of 2-3 inches (this is dependent on grass type! Many plant species require lower cutting)
- Sharpen your mower blade 1-2x annually
- Fertilize regularly
- Although out of your control, improved weather conditions can help your lawn recover
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