How To Control Lawn Diseases

Even we can be sick at some moments, especially when the season changes, as our bodies haven’t got familiar with the new weather conditions yet. This can also happen in some kind of plants, including grass. When the season changes, the conditions, which affect grass the most, such as the humidity level, precipitation, temperature will change suddenly. To make sure that you do not mistakenly think that brown spots on your green grass are just a small stress due to lack of water, let's learn about grass diseases and how to prevent them.


In fact, microorganisms exist in virtually every yard and garden. We usually call them fungi – a friend and foe of every lawn.

Actually, fungi is one of the important factors for healthy soil. It helps grass absorb nutrients existing in the soil. However, not all fungi are good. There is a pathogenic group which causes lawn disease. This group could develop at any time and widely spread when it rains or there is strong wind. It is also strong enough to survive through winter and stick to the soil for a long period. Here are some common diseases caused by the fungi that belong to this group:

Dollar Spot

Symptoms of this disease are small and circular spots with 1 to 5 inches in diameter. That is why they are called dollar spot. These spots may concentrate in a large area. They usually appear first in the early morning as a white and fine cobweb and then develop to a circular spot. After a few days, the area around this spot will become brown. The best conditions for this disease to develop are:

  • The temperature between 60 and 80 degrees F
  • Exceed moisture or water stress
  • Fog
  • Hard soil

To treat dollar spots, the fungicides should be used such as Bonide Liquid Copper – a natural formulation for many kind of plants, or Physan 20 – a common fungicide that is usually recommended for turf and grass.

Red thread

This disease is called red thread because you can find pink fungal crusts in the grass leaves. This disease appears first with a pink web of fungal thread, then spreads into patches 2 – 8 inches in diameters. The affected turf will initially turn into orange, yellow or light brown colors. It’s usually seen in cool temperature (60 to 70 degree F) and wet areas.

When red thread occurs, fungicide is definitely recommended. However, before using it, try to improve fertility (Nitrogen and Potassium) and the drainage system first. This method can be applied before August only. If this doesn’t work, then use fungicide which has trifloxystrobin for controlling red thread.

Fusarium Blight

This is one of the most common grass diseases in California. You can recognize it by seeing small, circular and grayish areas (from a few inches to one foot of diameter). At the dead part of the grass blade, it has a reddish, hard and tough rot. The perfect conditions for this fungus to develop are:

  • Frequent temperature of 85 to 95 degrees F
  • Full sunny day which leads to drought area
  • Thatch and grass residues

To treat this disease, the only solution is to apply fungicide during spring or immediately right after you see symptoms of Fusarium Blight.

Pythium Blight (Grease spot)

This disease could happen to every type of grass. Its symptoms are very easy to know: small circular spots continuously show on an area, just like footprints. Also, the grass leaves will wither quickly and turns into reddish brown. Once you take a grass root, you may find that the root is brown too. If the humidity reaches to a certain level, fungal mycelium might appear. Unlike the diseases above, this type of fungus love humidity.

Pythium Blight can be first be treated by watering, mowing and fertilizing. These natural methods may take time, but it’s safe for your lawn and yourself too. Fungicides are also the last option.

Rhizoctonia large patch

Rhizoctonia has symptoms which are quite different from the others. Firstl, it shows a small spot of grass is stressed. However, when it develops, it will enlarge to many feet in diameter in a short term. This fungus does not affect total grass roots, so after it happens, the center of brown area recovers, making this spot look like a ring. However, the plants become weak and easy to be pulled out. Though this fungus doesn’t infect roots, it reduces the quality of the soil. This disease loves cool temperatures, between 60 and 70 degrees F, with high humidity of soil.

To treat this Rhizoctonia, fungicide might be applied to receive a fast and direct result.


Normally, common grass diseases will not last for a long time. When the favorable conditions of these diseases are absent, the lawn can recover by itself. However, in most situations, the weather conditions allow these diseases to develop and become long-term. At this moment, it is hard for your lawn to recover. Therefore, we should manage and prevent these diseases from spreading widely and causing damage to our grasses.

Choose the right type of grass


From the beginning, we should choose the right grass type that is suitable to the local weather. This is an important factor to help you save your healthy lawn. For example, turf grass that is compatible with the local climate has better resistance to disease and has enough capabilities to adapt when the season changes. On the other hand, the right grass type will offer better growth and healthy lawns in the future.

You can identify the suitable types of grasses by checking the local weather conditions on the internet. Then compare it with the suitable growing conditions of grass seeds that are printed on the cover of packages. Alternatively, just ask the local farmers, specialists and sellers for more details.

Fertilizing correctly


Fertilizing is a common and simple way to enrich the nutrients in soil. When the soil has enough energy and “food” for the plants and grasses, the plants can grow up healthier and resist diseases better. Two times per year is a recommended feeding schedule for lawn health. If your children and pets often use the lawn as their playground, then you should feed the lawn 3 or 4 times per year. Fertilization is always needed, not only for the growth of grass seeds but also for the disease resistance and weather tolerance.

Make sure that you fertilize properly with the right amount and on the correct schedule. To know more about how to fertilize lawn, please check the article “How to fertilize your lawn” on our website.



Just like fertilizing, watering is not only required for the new seeded lawn, but it also influences the growth of the lawn and fungi! When the grass blades are wet, it is a good condition for diseases and pests to develop. Therefore, choose the right moment to water in order to make sure that it has enough time to absorb into the soil and leave no water drops on the grass blades later on. The best moment for watering is from 6 am to 9 am. To find out more about watering properly, please check the article “How to water your own lawn” on our website!



With a lawn mower or a reel mower, beside the aesthetic appearance, we can improve the disease resistance of the lawn because tall grasses offer good conditions for pests and fungi. Therefore, mowing to the correct height of grass will help reduce the development of bad microorganisms.

Normally, the recommended height of grass is between 5 and 9 centimeters. The mowing schedule should depend on the growth rate of each type of grass.



Preventing your lawn from disease is always better than healing it when the fungi have already occurred. Even if we can use fungicide to clear fungi and help our lawn recover, this solution is not always recommended as it also affects the health of your grass too. Although it’s hard to avoid lawn diseases, we are still able to control it effectively by applying these simple tips above. Besides that, please take time to observe your lawn everyday to detect the unusual symptoms of your lawn and have a proper reaction to treat it on time. Then, you will have a beautiful and healthy lawn yard.

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