Why Is My Lawn Grass Turning White?

You may have noticed white stripes, spots, or irregular patches on your lawn and wondered,” Why is my grass turning white?” Various factors cause the bleached effect. Diseases are a common cause of grass to turn white. Environmental conditions and physical damage, like incorrect mowing, also cause lawn grass to turn white.

Reverting white grass can involve treating it for disease, correct fertilizer application, supplementing mineral deficiency, or proper fertilizer application. Let’s delve into the main reasons your lawn looks like it was bleached.

Powdery Mildew

Mildew is the leading cause of grass turning white. Powdery mildew is caused by fungi and pops up on the grass as white, dusty patches. The fungi thrive in high humidity (90%), low light, and warm temperatures (60-70⁰ F).

Powdery mildew mainly affects grass growing in shady areas. Young developing grass is also prone. Some grass types, like Kentucky bluegrass, are more prone to mildew.

How do you fix grass infected with Powdery Mildew?

Spray the grass with fungicides containing Triforine, neem oil, and sulfur. These ingredients are effective in combating mildew infection. You can also use an eco-friendly alternative, such as baking soda mixed with horticultural oil.

Gray Leaf Spot

Gray Leaf Spot lawn disease is caused by a fungus and is common in new lawns. Infection appears as white spots outlined by dark edges. The fungus prefers warmth, humidity, over-fertilized and over-watered grass.

Gray leaf spot primarily attacks St Augustine grass but occasionally infects Ryegrass, Centipede grass, Bermuda grass, and Tall fescue grass.

How do you fix lawns infected with Gray Leaf Spot?

Treatment involves applying nitrogen to melt the fungi, but the better option is to prevent the symptoms rather than treat them.

Prevention involves minimizing water retention on the grass. You can achieve this by watering the lawn at sunrise and avoiding watering at night. Watering at these times ensures any extra water on the leaves evaporates.

Iron Deficiency Contributes To Grass Turning White

Mineral deficiency is an abiotic disorder that causes white, yellow, or brown spots on the grass, depending on the deficient mineral.

Nitrogen deficiency turns grass blades yellow, phosphorus deficiency turns them red or purple, and iron deficiency turns grass white. In extreme iron deficiency cases, leaves can turn almost transparent.

How do you fix iron-deficient grass?

First, perform a soil test to detect whether the soil needs more iron or a lower pH. Sometimes the soil may need both.

If there’s iron in your soil, but the soil is alkaline, add sulfur to make the soil acidic. Acidic soil makes iron more soluble and better absorbed by the grass.

If the soil lacks iron, you can add blood meal or chelated iron powder to the soil. Alternatively, spray the leaves with liquid chelated iron powder.   

Note: Don’t add nitrogen if your grass turned white. It will worsen the condition.

Fertilizer Burn

Fertilizer burn is another abiotic disorder. Grass can burn when excess fertilizer is applied, resulting in white stripes. It may also appear as if it was scorched by fire, or you can find dead patches of grass in extreme fertilizer burn cases.

How do you fix a lawn affected by fertilizer burn?

Fixing fertilizer burn involves reducing the amount of fertilizer left in the soil to deactivate the ongoing burning.

You can do this by scooping any visible fertilizer granules on the soil. Next, flush the soil using a garden hose or sprinkler. Apply one inch of water for four to seven consecutive days.

Give the lawn a few weeks to recover and reseed the affected areas if it hasn’t rebounded.

Drought

Drought is not a common cause of white grass because it occasionally happens when there’s inadequate rainfall. But, it applies if you live in a semi-arid area and don’t water your grass adequately.

The grass blade tips will fray and eventually turn white. That’s because the plant sacrifices the leaves for it to survive.

How do you fix drought-affected lawns?

Water deeply, about ½ to ¾ inches of water each session. Apply fertilizer to promote healthy roots that can suck water from the soil and practice core aerating your soil to reduce compaction and allow the roots to absorb nutrients.

Fusarium Patch and Fusarium Blight

Fusarium Patch and Blight are initiated by fungi and cause a bleached look on the grass. Both diseases thrive on heavily thatched lawns.

Fusarium blight starts as green-gray patches that turn white. It prefers warm conditions and attacks Kentucky bluegrass.

Fusarium patch turns leaf blades soggy before they take on a bleached look. This fungal disease prefers cool conditions and attacks Creeping bentgrass, Annual bluegrass, and Kentucky bluegrass.

How do you treat lawns infected by Fusarium Patch and Fusarium Blight?

Follow these tips to treat the Fusarium patch.

• Apply fungicide as soon as the patches appear. Avoid applying fertilizers high in nitrogen, such as urea. The fungi will also suppress if you apply potassium.
• Keep the soil acidic (pH 6 to 7.5) because alkaline soils are more susceptible to Fusarium patches.
• Remove thatch from your lawn because it blocks water drainage and encourages the growth of fungi.

Fusarium blight can be difficult to treat with fungicides. Proper lawn care is the cure. You can start by removing excess thatch to eliminate the fungi, avoid heavy nitrogen fertilizer application, and frequently irrigate to keep the grass moist.

Incorrect Mowing

Grass turns white if damaged during mowing. If you cut your lawn grass too short, the remaining turf can’t photosynthesize and therefore lacks energy. The grass then weakens and fades in color, eventually turning white.

Blunt mowing blades also cause lawn grass to turn white. Blunt blades don’t produce a clean cut. Instead, they fray the grass blades. The frayed edges dry out and turn white.

So, how do you mow correctly? Don’t cut lawn grass more than a third of the leaf blade height. Also, use a sharp mower blade to prevent fraying the grass edges.

Final Thoughts

Grass turning white loses its aesthetic appeal. The bleach-like patches are caused by disease, fertilizer burn, iron deficiency, and Fusarium patch and Fusarium blight diseases.

You can fix the condition by adding more iron to the soil, watering adequately, avoiding too much fertilizer application, and using fungicides.