When to Spray Grass for Leaf Spot

A well-kept lawn increases the beauty and appeal of the house, and makes the ideal setting for ornamental plants and flower beds. It takes effort to maintain a lush lawn and proper care can help you stay away from lawn problems, like fungi that cause leaf spot. But when leaf spot occurs, you must treat it promptly to conserve the lawn and prevent further damage, like root and crown rot or dead grass.

What Causes Lawn Leaf Spot

Leaf spot is caused by fungi and often affects many kinds of grass. Symptoms show on the sheaths and leaf blades as purplish-black spots, which enlarge and become elongated as the condition progresses. Affected areas turn white or tan at the center, while the outer rim stays dark in color. Other symptoms include die back of leaf blade tips and, when temperatures climb, typically 85 degrees F and above, the leaf spot fungi can attack the overhead causing plant death.

Spraying for Leaf Spot

When leaf spot fungus appears, you should start applying a fungicide immediately. Based on how often you mow the yard and the amount of rainfall received, the applications can range somewhere between each 5 to 14 days. For the fungicide to be effective, it needs to coat the grass blades. Once the leaf spot fungi have evolved to root or crown rot, fungicides are not effective.

Leaf Spot, Seasons and Temperatures

All kinds of fungi that cause leaf spot thrive during high relative humidity and when leaf blades stay moist. Drechslera poae and Drechslera siccans are the two common kinds of fungi that cause leaf spot in the spring. With these fungi, grass is more likely to die in hot temperatures. Bipolaris sorokiniana is a common fungus causing summer leaf spot and thrives in temperatures about 85 degrees F and higher. This fungus can cause root and crown rot. At the rainy portion of fall the same fungi that cause leaf spot in the spring are present, but generally much less severe. However, the fungal spores can stay on the grass and become active in the spring.

Tips to Maintain Your Lawn Healthy

A wholesome lawn is not as susceptible to leaf spot. Good maintenance will help keep the lawn green and verdant. Cutting the grass too close once mowing can weaken the grass, particularly during hot weather, so avoid cutting grass lower than 11/2 inches in cool weather and 2 inches in hot weather. When watering the yard, saturate the yard and allow it penetrate the soil. Over-watering the lawn can cause leaf spot. You should avoid watering during the late afternoon and evening hours.

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