Why does my grass develop yellow patches after I mow?

Improper mowing is probably the cause

You’re probably removing too much of the grass leaf at each mowing.

You should either mow more frequently so you never remove more than one-third of the leaf blade, or you need to level out your yard’s high spots because the mower is cutting too low as it goes over bumps.

My grass blades are turning yellow between the veins, but the veins themselves are remaining green. why?

Iron deficiency

You’re looking a common lawn problem: iron deficiency.

Usually, you’ll find this condition in soils with high pH. That’ s because in acidic conditions, iron tends to form compounds that plants can’t use.

If high pH isn’ t the problem, your iron deficiency may be caused by excess phosphorus, a poor root system, over-watering or use of water that has high levels of bicarbonate salts.

You should spray the lawn with a liquid iron supplement.

If an acidic soil is the root of your problem, drop the pH by adding ferrous sulfate or ferrous ammonium sulfate.

Why do grass patches turn yellow and die shortly after fertilizing?

Fertilizer burn

If the grass bordering these yellow areas is a healthy green color and the yellow areas don’t spread, fertilizer burn is to blame.

Whenever excessive amounts of these materials contact grass, they cause the blades to dry out and die.

You can prevent burn by picking up spilled fertilizer, applying fertilizer according to label directions and thoroughly watering the grass after fertilizing to wash it into the soil.

After the snow melted, pale yellow patches trimmed in pink appeared on my lawn. what' s the problem?

Snow mold

You’ re probably looking at Fusarium patch (pink snow mold).

Generally a problem in late winter or early spring, this grass disease usually attacks lawns wet from snow, rain or poor drainage.

Grass blades are usually light tan and stick together, and a white cottony growth may cover the blades.

By the time you observe Fusarium patch in the spring, it’ s usually too late to apply a fungicide. That’ s why proper lawn management is so important.

To reduce the danger of this disease, keep your yard mowed and aerated in the fall, and avoid excess fall nitrogen applications. Frequent mowing can help control the problem too.

Why are circular straw-brown spots roughly 8-to-10 inches wide appearing in my lawn?


If you’ ve had dogs in the area, you’ re probably seeing dog urine injury.

To correct the problem, water the affected areas thoroughly to wash away the urine.

While this won’ t completely eradicate the brown discoloration, surrounding grass will eventually fill the affected spots.

To prevent further problems, try to keep dogs off the lawn.

If canines can’t be blamed, you may have dollar spot or Fusarium blight.

My yard has large, circular patches of brown grass. the leaves first appear water-soaked, but dry and turn dark brown. what should I do?


If you live in a warm, humid area, you may have brown patch.

This fungus attacks lush, tender growth, so you’ ll usually find it in yards with excessive nitrogen.

Often only the blades are affected and the grass will recover. However, severe infections can kill your grass.

To stop brown patch, you’ ll need a fungicide with chlorothalonil and at least three treatments spaced seven-to-10 days apart. To prevent it, avoid heavy doses of nitrogen fertilizer, keep your thatch under control and aerate your yard regularly.

Why does an orange dust fill the air when I mow?


If your grass blades are covered in an orange powder, and the reddish-brown lesions underneath don’t rub off, you’ve got rust.

The fungi to blame are usually active during humid weather.

Grasses under stress from nitrogen deficiencies, moisture shortages or close mowing are most susceptible.

Rust develops slowly, so in many cases, frequent mowing’s, adequate water and an application of a high-nitrogen fertilizer can stop the problem. Frequent mowing can help control the problem too.

Why is my grass turning gray?

Tip burn

If the tips of your blades are pale yellow or gray, perhaps with red or yellow margins, and you see tiny black dots, you can bet it’s septoria leaf spot.

Also known as tip burn, this fungus can infect most northern grass species. The combination of cool, wet weather and unfertilized lawns usually bring on the disease.

A fungicide with mancozeb will control the problem, but you may need three or more treatments. Frequent mowing can help control the problem too.

Why is my grass pale green in color and growing more slowly than usual?

You need to fertilize

Odds are that a nitrogen deficiency is to blame.

You’ll need to apply a lawn fertilizer to boost soil nitrogen levels.

My lawn has turned a bluish-green color and footprints make a lasting imprint?


If the grass recovers during the evening but darkens and wilts under the daytime heat, your lawn is under drought stress.

You’ll notice drought damage first along sidewalks and driveways (the hottest and driest areas of the lawn).

Water your lawn immediately.

Why does my grass look like it's been dusted with flour?


Powdery mildew is probably to blame.

This fungus-caused disease makes white or gray mold appear on grass blades. As the disease progresses, leaves turn yellow, wither and die.

Slow (or non-existent) air circulation, shade, and high humidity contribute to the problem.

Chemical controls are available, but your best bet is prevention. I suggest you plant shade-tolerant grass varieties, follow nitrogen fertilization guidelines and selectively prune shrubs to increase air circulation.

Why is my grass thinning out?


More often that not, the thinning grass is a sign of heavy thatch.

If your thatch layer is thicker than a ½ inch then it’s probably slowing grass growth by restricting the movement of water, air, and nutrients in the soil.

Remove thatch from your lawn.

Why does my grass become thin and develop bare spots in heavily traveled areas?


Compacted soil is the culprit.

Aerate heavily trafficked areas annually.

A number of circular patches are forming in my yard. the centers remain green, but the edges are dying. what should I do?


This tell-tale “frog-eye” pattern is caused by several fungi.

Called Fusarium blight, this is generally only a problem from June through August.

Two of the most susceptible grass varieties are bentgrass and Kentucky bluegrass.

Lawns are particularly susceptible to the disease when they are under stress from drought. Once these fungi go to work in your yard, you may have trouble stopping them.

Your best bet may be to re-seed with resistant grass varieties. Even then, I’d suggest treating the whole lawn with a fungicide, control is difficult to achieve.