Common Lawn Diseases

While many strive to have perfect landscaping, occasionally lawn diseases will sneak up and wreak havoc. By learning what to look for and the environment that diseases thrive in, you’ll be able to call the experts at Grasshopper Gardens as soon as you notice an issue.

Common Lawn Diseases

Red Thread

Red Thread is a fungal infection found on lawns and other turfed areas. There are two stages; the first is thin, red, needle-like strands extending from the grass blade. The second is visible as small, pink, cotton wool-like mycelium, found where the blades meet.

What to look For

  • Irregular patches of brown or yellowing grass is the first sign of Red Thread
  • Pink/brown patches 1 to 4 inches in diameter but up to 2 feet

Contributing Factors

Red Thread thrives in cool, wet, spring and fall temperatures. Areas that are mostly in the shade and low in nitrogen are also susceptible to Red Thread.

Dollar Spot

Dollar Spot causes sunken, circular patches that measure up to 2 inches in diameter. The patches start off brown in color before turning to a straw color.

What to look For

  • Small, circular patches
  • Small lesions on leaves that turn from yellow green to straw colored with a reddish-brown border

Contributing Factors

All species of warm and cool season turfgrass are susceptible. The disease is favored by warm days, cool nights, and intense dews. Low nitrogen and dry soil are also contributing factors.


Rust lawn diseases are caused by fungus. The fungi symptoms start as small yellow spots on blades of grass. The spots become elongated and eventually rupture into clusters of rust-orange spores.

What to Look For

  • Light yellow flecks on leaf blades
  • Thinning turf as individual leaf shoots die

Contributing Factors

Rust diseases typically occur around mid-summer through late fall. Rusts favor moist, low light areas with temperatures between 65° and 86° Fahrenheit. It can also occur any time turf is under stress, like during long dry periods.

Powdery Mildew

Powdery Mildew is a fungal disease that can affect a wide variety of plants. The fungal spores are spread to other plants by wind, water, and insects. Those with vegetable gardens should be alert as zucchini, beans, cucumbers, squash, pumpkins, and tomatoes are highly susceptible.

What to Look For

  • The first sign of powdery mildew is individual tufts of fine, white mycelium
  • Leaves will have a grayish-white appearance
  • Dead patches of turf
  • Thin patches of turf

Contributing Factors

Powdery Mildew occurs in cloudy and humid conditions with temperatures between 60° and 72° Fahrenheit. In upstate New York this is typically in the spring and fall. It is also common in areas with poor air circulation.

Pythium Blight

Pythium Blight first appears as small black or purple spots before expanding into a large, irregular areas. The disease spreads rapidly along drainage patterns and can be tracked by equipment. It causes widespread damage to turf very quickly.

What to Look For

  • Greasy, brown circular spots that are initially about 2 inches in diameter and then rapidly enlarge in size
  • Spots are water soaked and dark in color in the morning
  • Form fluffy white masses
  • Irregular areas of dead turf
  • Infected patches may appear orange in color 

Contributing Factors

Pythium Blight appears suddenly during hot and humid weather. It favors night temperatures above 68° Fahrenheit and is found in wet areas of turf.

Pink Snow Mold

Pink Snow Mold is a fungus associated with melting snow or cold, wet periods. The fungus can survive as dormant mycelium in infected plants and plant debris, flourishing once the right conditions occur. For this reason, it’s especially important to have Pink Snow Mold professionally treated so it doesn’t continue to wreak havoc on your lawn year after year.

What to Look For

  • Yellow, tan, or salmon-colored water-soaked patches
  • 1 to 8-inch diameter patches

Contributing Factors

Pink snow mold occurs when temperatures are below 60° Fahrenheit. It is more severe where snow has fallen on unfrozen soil or in cold, rainy weather.

Gray Snow Mold

Gray Snow Mold is a cold weather fungus that primarily affects cool-season grasses. It is particularly problematic when there is a heavy, deep snowfall before the ground has completely frozen. The weight from the snow combined with all of the moisture creates an ideal environment for Gray Snow Mold.

What to Look For

  • Light brown or gray patches that measure than 10 inches in diameter
  • Rust, brown, or black colored sclerotia can appear on infected leaves

Contributing Factors

Snow cover is necessary for Gray Snow Mold to cause damage. It is most severe when snow cover lasts more than 90 days.

Summer Patch

Summer Patch is a highly destructive root fungus that will kill your grass.

What to Look For

  • Circular or irregularly shaped patches that measure from several inches to several feet in width
  • Have an initial appearance of slow growing, thinned, or wilted grass
  • Leaves appear yellow or brown with dark brown roots

Contributing Factors

Summer Patch begins to appear when soil temperatures exceed 65° Fahrenheit. It is commonly found in areas that are sunny, exposed, and with high soil moisture, high soil pH, compaction, poor drainage, and low mowing height.


Mushrooms are the reproductive part of fungi that live in soil. Most of the time the fungi remain underground, breaking down organic material. However, after heavy rain the mushrooms can burst through the ground, becoming visible.

What to Look For

  • Gray, tan, white or brown fungi popping out of the ground

Contributing Factors

Mushrooms thrive in wet, shady conditions. They also prefer compacted soil, which can occur due to standing water. Mushrooms aren’t always bad, though. They help break down organic material and make your soil more productive. If standing water and drainage aren’t issues you can choose to simply knock the mushrooms over and wait for the sun to dry them up.

Common Insects in New York

In addition to mold and fungi, certain insects native to New York can damage your lawn. Keep a close eye out for any of the following and contact us if you’re experiencing an issue.

Sod Webworms

Sod Webworms are the immature stage of several small, tan colored moths. These worms are most common in the summer months. Larvae are grayish brown to dirty white with parallel rows of dark brown spots on the abdomen.

What to Look For

  • Small, ragged brown spots in the turf
  • Large, dead patches of turf
  • Larvae on the patches of dry or dead turf
  • Green fecal pellets in the thatch
  • Small moths flying above turf during the evening

Contributing Factors

Webworms are common from late spring through the beginning of fall. Damage typically occurs in sunny areas. Ensure your lawn is well watered and fertilized so it has the proper nutrients to protect against Sod Webworms.

Chinch Bugs

Chinch bugs are small insects often found at the margin between damaged and healthy grass and will release a pungent defensive odor when disturbed. They can cause serious damage to lawns by sucking fluid from the blades of grass and injecting a chemical that will turn the leaves brown and kill them.

What to Look For

  • Small, black and white insects that move quickly when disturbed
  • Immature Chinch Bugs will have bright orange bodies, no wings, and a white band across their backs
  • Grass that appears to be turning brown and dying from the tip down to the roots

Contributing Factors

Chinch bugs are prevalent from April through October and thrive in sun and heat. They are rarely found in shady areas of lawns.

White Grubs

White grubs are the immature stage of several beetle species, including the Japanese beetle and June beetle. The grubs are white, C-shaped insects with a chestnut colored head and 3 pairs of legs that are clearly visible. They cause damage to turf by feeding on the root systems.

What to Look For

  • White insects with c-shaped bodies
  • Wilting grass that does not recover after rainfall or irrigation
  • Dead patches of turf at the end of summer or beginning of fall
  • Sod becomes easy to pull up, revealing the white grubs beneath

Contributing Factors

Beetles emerge in the early summer, feed on plants in the garden, and lay their eggs in the soil in the lawn. Later in the summer the grubs hatch and begin to feed. Apply a preventative grub control and ensure your lawn is properly maintained.


Ants are very common in New York and don’t typically pose a problem. However, if they begin to build hills in your turf, they can cause root damage. They settle in large numbers and build elaborate labyrinths in the root systems. If the hills get too big, they can be a hazard to lawn mowers.

What to Look For

  • Mounds of what appears to be sand throughout the turf

Contributing Factors

Ants prefer dry, well-drained soil in an undisturbed, low traffic area.


Ticks do not harm your lawn, but they do carry numerous diseases including Lyme which are harmful to humans and pets. Ticks are typically controlled by restricting animals that carry them or by applying pesticides along the yard perimeter.

What to Look For

  • Ticks are small, black, or brown insects with 8 legs
  • Be on the lookout for any white-tailed deer, as they carry the Deer Tick which transmits Lyme Disease

Contributing Factors

Ticks favor habitats in the tall grass and brush of your wood line while they wait for their next host, both animals and people. They also live on rodents and hoofed mammals such as deer. You can build fencing to keep out deer and mow your lawn to eliminate tall grass and brush. We also offer tick control applications to prevent the insects from entering your lawn.

Clover Mites

Clover Mites are a dark, reddish brown pest. They’re smaller than a pinhead and do not pose a threat to human health. They can, however, harm your turf and landscaping. Clover Mites eat leaves and various types of flowers, leaving behind what look like streaky gray marks.

What to Look For

  • Streaky gray marks on turf
  • Large patches of dead grass
  • Flowers and turf with ragged edges from bite marks

Contributing Factors

Clover Mites thrive on moisture and plant materials. Reduce moisture by cleaning leaves around your home, focusing on areas such as wells and windows. River rocks used in landscaping can also trap moisture, so it’s important to clean around these areas.


Mosquitoes are a general nuisance for many come late spring and into the summer. They make lawn work a pain and take the enjoyment out of sitting on the deck in the evening. While they can’t be completely eliminated, there are steps you can take to control mosquitoes in your yard.

Contributing Factors

Mosquitoes thrive in standing water. By reducing the amount of standing water around your home, you will be able to minimize breeding sites and the number of mosquitoes. Places to look include gutters, tree holes, pot holes, bird baths, and any toys left on the lawn that are collecting water.

Other Common Lawn Problems

The following are other common lawn problems many people in New York experience. They can be easily avoided with a little knowledge and preventative action.

Heat/Drought Stress

Heat stress is caused by the heat and humidity when the lawn lacks water. A lawn suffering from heat stress is more prone to disease, insects, bare spots, and weeds. It is important to water your lawn properly in the morning to keep the turf hydrated and avoid heat stress.

Dull Mower Blade Damage

A dull mower blade may cause lawn deterioration and give the turf a brown cast. It also makes the lawn more susceptible to disease by tearing grass and leaving a frayed edge. Mow your lawn consistently, ensuring the blades are 3 inches high after cutting. Mowing to the proper height can reduce weed problems and give your lawn a healthy appearance.

Cutting the Lawn too Short

Mowing removes part of the leaf that is responsible for the plant’s food production through photosynthesis. Removing too much of the leaf affects root growth, draws on stored energy in the roots and eventually starves the grass. If grass has grown particularly long, it should not be cut to three inches immediately. Instead, raise the mowing height and gradually reduce the height over several cuttings to prevent scalping and cutting too short.

Heat Tracking

Heat tracking is damage caused by driving on a lawn when it is wilting. If you notice your lawn is starting to appear blue or you see footprints on the turf, it’s likely that any sort of future traffic will cause heat tracking. Avoid mowing during the hottest time of the day and properly water your lawn.

Shallow Root System

Surface roots make lawn maintenance a challenge and can be a tripping hazard for anyone walking through the grass. They can also grow into sidewalks, causing them to crack and break. Some trees are prone to shallow roots while others develop surface roots under certain conditions.

Surface roots are common in compacted or clay-based soil. When the roots within the first few inches of soil get large enough, they break through the surface. Rain and erosion will further expose the roots. If there is a lack of oxygen in the soil, roots will grow up to the surface to get enough oxygen and keep the tree alive.

If you have shallow roots in your lawn, don’t cut them. Doing so will leave the roots prone to disease and harmful insects. It can also affect the tree’s stability, making it more likely to fall over in a storm. Topdressing the base of the tree or using mulch are effective ways of treating shallow root systems.


Shady parts of your lawn and landscaping are susceptible to moss. It tends to grow during the gray, wet days of late fall and early spring. It won’t kill your lawn, instead filling in the areas that are thin and preventing new grass from growing. The presence of moss is a good indication that there is a larger problem, such as compacted soil, poor drainage, low soil pH, or not enough sunlight.

The best way to prevent moss is to treat the underlying problem. Trim branches or remove other items that are preventing the sun from reaching your lawn. Feed your lawn regularly and keep grass at the proper height to ensure it remains healthy. Lastly, correct any drainage problems to avoid having areas are the persistently damp.