Fertilizer

• Fertilizer is often the root of grass issues. Sometimes it is a lack of fertilizer that causes problems, and other times it is the application of too much. When your lawn does not have enough available nutrients, it can wilt and turn yellow or brown. If you apply too much fertilizer, it can actually burn your grass and damage it. The type of grass you have in your yard will determine what type of fertilizer you should use and how much you should apply. Read the package carefully to make sure you buy the correct type of fertilizer for your lawn and that you apply the correct amount.
  
  

Water

• If your grass is not watered enough, it can turn yellow or brown. In periods of dry weather, you should water your lawn often. Be sure not to overwater. Too much water can make your grass more susceptible to fungal infections such as powdery mildew. The soil in your yard should be moist, but not soaked.
  
  

Rhizoctonia Yellow Patch

• If your grass is mostly green with yellow rings or patches, it might be Rhizoctonia yellow patch. This disease infects Kentucky bluegrass, and it is caused by a fungus. It typically infects plants during periods of cool, wet weather. Avoid using nitrogen fertilizer in the spring and water frequently, but lightly. Deep watering causes excessive moisture, which can make this disease worse.
  
  

Summer Patch

• Summer patch is another disease that can cause yellowing of grass. It is a fungal infection that typically occurs in the hottest months of the year. It causes large yellow patches of grass about 6 to 12 inches wide. This can lead to death of the yellow patches if the weather continues to be very warm. Since excess water can worsen this condition, water grass very lightly during hot weather.
  
  

Powdery Mildew

• Powdery mildew is a fungal infection that can invade many types of plants, including grass. It causes the blades of grass to turn yellow, and you may notice a fine white fungal growth that looks like a powdery white cotton candy. It is especially common in very damp areas where there is little air circulation, shady areas and areas of high humidity. Plant grass varieties that are resistant to powdery mildew, and prune back any trees or shrubs that may be shading your lawn in infected areas.