The appearance of yellow patches on a lawn is always cause for worry. The cause must be determined quickly in order to remedy the situation. Is the damage due to drought, insects, disease or something else?
Obviously, a lawn that is not properly watered will turn yellow during the summer months. Apart from being visually unappealing, this is completely normal and does not affect rooting. As soon as the lawn receives moisture, it will come back to life.
If, however, the lawn is watered and the patches do not turn green again, or the damage seems to intensify, there is surely a justifiable reason.
Listed below are some of the most common explanations.
1. Frost
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Problem
- Presence of irregular yellow patches on the lawn.
Symptoms
Yellow patches of burnt grass varying in size from small to large.
Appearance
As the ground thaws in early spring.
Cause
Frost
Detection
Small to large patches that do not become green after the ground thaws.
Solutions
- The last mow before winter must be done well before the first frost and the grass should be left at a height of 2.5 to 3 inches.
- In order to keep this height, never mow the lawn after the first frost.
- Keeping the grass longer, allows for greater root development, and thus better protection from frost.
- Topdress and seed the affected areas in the spring.
2. White grubs
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Problem:
- Presence of irregular patches on the lawn.
Symptoms
Presence of brownish irregular patches on the lawn, often accompanied by sections of grass that have been overturned or torn-up by racoons, moles or skunks.
Appearance
Early-spring as well as late-summer and early-autumn.
Cause
White Grubs, which are beetle grub larvae, that later transform into what is commonly known as the June bug.
Detection
You will be able to effortlessly lift patches of grass, without any root resistance. Underneath these patches, you will find c-shaped white larvae.
Prevention
- Choose one of our fertilization programs, which will keep your lawn dense and healthy.
- Keep your lawn height at a minimum of 3 to 3.5 inches.
- Do not use outdoor lighting on your property whenever possible, during the egg-laying period (mid-June to mid-July) because the light will attract the beetle (June bug).
Control
- You may choose to apply nematodes (microscopic worms) during the months of May and August when the temperature of the soil is ideal.
- There is also an effective insecticide that controls white grub.
3. Chinch bugs
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Problem
- Presence of yellow patches on the lawn.
Symptoms
Irregular-shaped, dry yellow patches that spread rapidly.
Appearance
Mid-summer during hot and dry periods, typically late-June to late-July.
Cause
Chinch bug
Detection
Lawn damage shows up as irregular yellow patches, which begin in late-June and spread over the summer, even if the lawn is watered regularly. They start off a bright red and then darken to orange or brown, finally to black with a white band across the back when fully mature. They are approximately ¼ of an inch in size. Look for them in the greener parts of the lawn, near damaged areas. The adult chinch bug does virtually no damage.
Prevention
- Choose one of our fertilization programs, which will keep your lawn dense and healthy.
- Keep your lawn height at a minimum of 3 to 3.5 inches.
- Overseed damaged areas.
Control
- Apply soapy water morning and evening. Repeat for 5-7 days.
- In case of a major infestation, an insecticide is required.
4. Sod webworms
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Symptoms
- Presence of irregular patches on the lawn.
Appearance
Late September to late October.
Cause
Sod webworms.
Detection
The early visible signs are reminiscent of the damage caused by white grub. With sod webworms, however, you will notice patches of lifeless grass that easily detach from the soil, revealing silken masses to which particles of soil and green-coloured excretions will adhere. The silk is produced by the sod webworm caterpillar, a 2 cm long insect with a dark brown head and slightly hairy whitish-coloured body. In late-May or early-June until August, you will notice the presence of small whitish nocturnal moths near the surface of the lawn. This is a sign of a possible infestation, of which damages are likely to appear in autumn. A thick healthy lawn can withstand the presence of a considerable number of sod webworms without suffering.
Prevention
- Choose one of our fertilization programs, which will keep your lawn dense and healthy.
- Keep your lawn height at a minimum of 3 to 3.5 inches.
- Aerate your lawn.
Control
An insecticide is required.
5. Drought
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Problem
- Presence of large patches of dry grass, especially in areas deprived of shade.
Symptoms
Unshaded areas of lawn seem dry and dead.
Appearance
In extended hot periods and heat waves.
Cause
Following an extended dry period without rain, lawns have a tendency to become yellow and dry. It is important to understand that approximately 65% to 100% of a lawn’s water needs are met by rainfall. During dry periods, grass becomes dormant and turns yellow in order to better resist stress. It will, however, return to normal once precipitation begins.
Prevention
- Keep lawn long
- Avoid mowing, especially if grass is dormant, because it will weaken the lawn.
- Aerate the soil so that water can penetrate better.
- The lawn needs 2 to 2.5 inches of water per week, about 1 hour per inch including rainfall. Adjust your sprinklers accordingly, while respecting your municipal regulations.
- If the soil is in poor condition, add compost by topdressing the lawn regularly.
6. Dog urine
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Problem
- Yellow round spots on the lawn.
Symptoms
Presence of yellow burnt spots of grass.
Appearance
All throughout the season.
Cause
Dog urine. Its acidity will create roundish yellow spots, scorching the grass affected.
Detection
The appearance of roundish spots that are greener than the rest of the lawn, because the nitrogen contained in dog urine reacts as a concentrated surcharge in a specific area. Afterwards, these same grass spots will burn and turn yellow.
Prevention
- Have a specific area where the dog is allowed to do his business.
- Pour 2 or 3 cups of water over the area after the dog urinates.
- There are products (pills or bone-shaped cookies) sold in certain pet shops that prevent the affected grass from burning (NaturVet).
Control
Topdress and seed the affected areas.
7. Dollar spots
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Problem
- Presence of round spots on the lawn.
Symptoms
Clearly delimited discolored spots that are green to brown in colour and 2 to 5 cm in diameter, reaching up to 15 cm. In the case of a strong attack, spots may converge. Affected areas clearly stand out from a healthy lawn. A spider web looking mould appears on the lawn when the humidity level is high.
Appearance
Spring and autumn, during the lawn’s main growth period.
Cause
Dollar spots (Sclerotinia homeocarpa).
Detection
The grass stem dries out from the middle. The mold (mycelium) can also produce a toxin that blocks the root system, which causes the plant to quickly dry out.
Prevention
- Choose one of our fertilization programs, which will keep your lawn dense and healthy.
- Keep your lawn height at a minimum of 3 to 3.5 inches.
- Water regularly (once a week).
- Aerate the lawn.
Control
Topdress, sow new grass seed and add potassium.