How to Identify and Fight Common Lawn Diseases

Lawn diseases come in multiple forms, and the best way to rid of them is to identify what the disease is and the what’s causing it. 

Here are some of the most common lawn diseases and how to fix them:

Brown Patches

Brown patches are very common - especially if you have cool-season grasses like in the Pacific Northwest. These patches consist of circles of dead, hollowed grass that are sometimes up to 20 feet wide. The most commonly affected grasses include:

  • Bentgrass
  • Bermudagrass
  • Perennial ryegrass
  • Tall fescue
  • Kentucky bluegrass
  • Fine fescue grasses
  • St. Augustine grass

Brown patch lawn disease becomes prevalent in late spring and throughout the summer when it gets hot and humid. It’s caused by overwatering, overfertilizing, or by allowing your thatch to become thicker than ½ an inch. Mowing your grass too short also leads to brown patch lawn disease, because the grass blades won’t be long enough to shield the soil from burning. 

Red Thread

Red thread is also common in the PNW and affects most of the grasses listed above. This disease is most common in nutrient-poor soils and can be identified by their thin, red hairs extending from the grass blades. 

The easiest way to treat red thread is to fertilize your lawn with the proper amount of nitrogen, which is prominent in grass clippings. You can avoid or cure red thread by keeping your soil nourished, but be aware that it can take up to two years to fully eradicate. It’s also treatable with chemicals, but that’s not recommended unless you’re a lawn-care professional. 

Gray Leaf Lawn Disease

Gray leaf occurs when your grass blades develop tiny, bleached spots with dark brown edges that turn gray when wet. It most often affects tall fescue grasses and perennial ryegrass, and is caused by a combination of too much shade, overfertilizing, overwatering, and poor air circulation. 

Gray leaf occurs most often when there’s both high temperatures and high precipitation, it’s also pretty common in the PNW. 

Rust Diseases

If you begin to notice yellow or light green patches on your lawn, take a closer look. If there are orange-yellow rust spores on the individual blades of grass, your lawn has a rust disease. 

Rust can appear as early as spring if your lawn isn’t properly fertilized, but you’re more likely notice it towards the end of summer/early autumn, especially in areas that get a lot of shade. The best way to prevent a rust disease is to properly feed your lawn throughout the year. 

Snow Mold

Snow is more common in the PNW than you’d think. Symptoms of snow mold include seeing pinkish, circular spots on your lawn, which can be a foot in diameter or longer. The blades get their pinkish color from turning reddish brown when overly watered or rained on, then tan, and finally pinkish when fungus appears. 

Cool, wet climates are prime targets for snow mold, especially if it gets covered by a blanket of snow. If you lawn has too much shade or if you’re not draining it, it can exacerbate the problem. 

Combating Lawn Disease

The best way to fight or prevent lawn disease is to practice excellent lawn care. Don’t overfertilize, overwater, or fail to give your lawn the nutrients it requires. Dethatch when needed, and mow high and mow frequently.