How to Identify and Treat Zoysia Grass Diseases

Introduction to Zoysia Grass

What is Zoysia Grass?

Zoysia grass is a warm-season turfgrass that has dense growth, durability, and a lush green color. Native to Asia, it has been popularized in the southern and transition zones in the US, as it has a high tolerance to drought, foot traffic and moderate shade. It is slow growing and covers well, thus making it a desirable variety for lawns, golf courses and for parks.

The distinctive feature of Zoysia is its fine texture and heat tolerance. It does best in full sun but will more so tolerate some shade compared to Bermuda grass. Zoysia, while giving you the picture perfect lawn, is not not without its problems especially diseases that can turn your beautiful, green lawn into a patchy nightmare.

Benefits of Zoysia Grass Lawns

Zoysia grass is more than skin-deep, It’s the life of the party for homeowners who want an attractive turf that requires little care. Here’s why:

• Drought Tolerant: When it’s established, Zoysia doesn’t require a lot of watering.

• Stout and leafy: It naturally chokes out weeds as it grows close.

• Wear: Good for backyards that are used by kids, dogs and for high foot traffic.

• Slow growth: Translates to less mowing than many other varieties.

• Salt-tolerant : Also good for planting in coastal areas.

But with these and other pluses, it is important to keep in mind that the best turf grass can fall victim to fungal and bacterial diseases. Learning about Zoysia’s illness and why and how it gets sick is the first step in both treatment and prevention.

Zoysia Grass Diseases Explained

Reasons Why Zoysia Grass Gets Diseases

Zoysia is hardy but not invulnerable. Diseases often originate when the environment surrounding the grass becomes too conducive for fungi and other pathogens. Imagine it this way: Zoysia is like a robust athlete, but even strong athletes can be made sick if they’re overworked, malnourished or stressed out. The same goes for lawns.

Diseases will pop up most often with stressed Zoysia. You can stress a lawn in various ways too much rain, overwatering, poor drainage, high humidity, thatch, lack of nutrients. A stressed lawn is an open door for diseases.

Diseases Caused by Common Conditions

Let’s look at the major factors occurring that cause Zoysia grass diseases:

• Too much moisture: Overwatering or ongoing rain provide a place for fungi to thrive.

• Wrong mowing: Letting your grass grow long is dark and cool and not conducive to its general health.

• Bad soil drainage: Stagnant water rots roots quickly.

• Thatch buildup: If dead grass is covering the ground, the buildup can prevent moisture from drying and can cultivate fungi.

• Nutrient imbalance: Too much nitrogen, too little nitrogen, or an excessive application can throw the lawn off kilter.

• Shade and sunlight: Zoysia is a sun lover; in the shade, it remains wet and is disease prone.

Now that we know what makes Zoysia weak, we can drill down into the most prevalent diseases of Zoysia, and learn how to recognize them.

Primary Zoysia Grass Diseases (and How to Identify Them)

Brown Patch Large Patch Disease

Symptoms

• By far, this is the most common disease of Zoysia owners. “Large patch,” which is commonly mistaken for brown patch, is a result of the Rhizoctonia solani fungus. The symptoms appear as large, circular patches of brown, dead-looking grass. These patches can be several inches, to several feet in diameter. You may see a dark, reddish outer ring that is where the fungus is actively growing.

Causes

• Large patch prefers warm, wet weather especially cool nights, such as in spring and autumn, when temperatures drop but soil remains warm. Over watering, excessive thatch, poor drainage are the primary causes of this disease. Furthermore, over application of nitrogen in the Fall can exacerbate the issue.

Rust Disease

Symptoms

• Rust disease is named for the orange or yellowish powder that appears on grass blades. As you meander across the reading lawn and infected lawn, it is likely that this “rust” can rub off on your shoes. Infected grass appears sickly and dull, and, one at a time, the blades will perish to give your lawn a straggly, stringy appearance.

Causes

• Rust appears when the grass is growing slowly this frequently occurs because of low levels of nitrogen or drought stress. It likes the mild, the shade, so you’re most likely to spot it in early fall or late spring.

Leaf Spot

Symptoms

• Leaf spot results in tiny, brownish-purple lesions developing on the leaf blades. They eventually enlarge and coalesce to produce a general blighting and thinning of the turf. You’ll also notice yellowing and even rotting of the leaf tips.

Causes

• Humid weather, as well as wet conditions combined with high levels of nitrogen in the soil, encourages the disease. Too much water and poor air circulation can make the perfect setting for the stinkpot to spread.

Dollar Spot

Symptoms

• This is a disease that will appear as dime-sized to silver-dollar-sized patches of dead or dying grass. The patches may initially look like sunburn or bleach damage. As it advances, it can expand into broader dead zones.

Causes

• Dollar spot likes soil low in nitrogen and dry days followed by nights of high humidity. Bad mowing practices, such as mowing with a dull mower blade, can also result in this concern.

Zoysia Decline

Symptoms

• This is more an extended simmer than a bolt out of the blue. You’ll see the grass turning yellow and beginning to thin out over months to even years. You end up with bare patches that never fill in.

Causes

• Zoysia decline is frequently caused by chronic infection with fungi, and poor lawn maintenance. It can also be caused by compacted soil, bad drainage, or a lot of aggressive thatch. “You tend to have a combination of factors that have accumulated over time,” she says.

How to Diagnose Zoysia Grass Diseases

Visual Signs to Watch For

Identifying a disease early can mean the difference between a simple repair and ripping up the lawn and starting from scratch. For the most part, Zoysia diseases provide telltale symptoms if you know what to look for. Here’s a rundown of some of the main ways to spot when your Zoysia lawn is in poor health: 

• Color changes: Any time parts of your lawn begin to change color from green to yellow, orange, or brown, it’s time to investigate.

• Patterns: Circular patches, rings or spots. The majority of fungal diseases form characteristic patterns.

• Texture changes: Diseased turf may feel slimy, have a dry texture or have a broken surface.

• Powder or residue: Certain diseases, like rust, leave behind an identifiable powder on your shoes or fingers.

• Growth problems: Slow or patchy growth, particularly if they are intermingled with healthy grass, is a telltale sign.

Begin early in the morning, when dew is out it makes it easier to see fungal activity. If in doubt, use your fingers or a magnifying glass to inspect the blades.

When to Call an Expert

If you are uncertain or if the disease is rapidly progressing even after you have attempted some basic remedies, don’t hold off too long give your lawn care service provider a call. They can:

• Get a soil test to determine pH and nutrients.

• If the disease is suspected, correctly identify it with the help of laboratory tests.

• Recommend specific fungicide(s) and treatment(s).

• Ask for tips on preventing further incidents.

• In fact, DIY efforts can sometimes backfire if the wrong treatment is employed. So if you’re not sure, it doesn’t hurt to call in a pro to revive your Zoysia.

Diseases in Zoysia Grass: Learn How To Treat Common Zoysia Grass Diseases

Natural and DIY Treatments

Natural methods are often the first preference of many homeowners before trying chemical solutions. Below, some effective home remedies:

• Neem oil or compost tea: Spraying such fungicides onto the lawn can minimize the activity of fungus.

• Baking soda spray: Add a tablespoon of baking soda to a gallon of water and several drops of dish soap. Spray this mixture on where ever you have fungus.

• Ground cornmeal: There are gardeners that swear by sprinkling ground cornmeal as a method for suppressing fungi.

• Increase air flow: Prune nearby shrubs or trees that produce too much shade or catch humidity.

• Water wisely: Water in the early morning and allow the grass to dry out during the day to prevent lawn-encouraging-disease-producing dampness.

To function, these approaches are most effective early on in infection, or they can be used preventively.

Chemical Fungicide: Uses and Application

Once that disease or pest gets out of control, or if all the natural or chemically innocuous remedies don’t help, then it’s time to face one fact in the garden: the formulaic causes can only lead to one prescription — the big guns. And when I say “big guns,” I mean it: chemical fungicides. Here’s how to do it right:

• Choose the right product: Find a fungicide labeled for the disease (Propiconazole for large patch, Azoxystrobin for leaf spot).

• Read the label: Be sure to follow the directions to the letter, so you don’t apply it too often or endanger your beneficial lawn microbes.

• Timing is key: Apply fungicide when signs of disease first appear or early spring/fall when fungi is most active.

• Rotate fungicides: Don’t use the same fungicide back to back to prevent resistance. Alternate between products with different active ingredients.

• Pro tip: Keep a log of what you did, when, how it turned out. It will also help you better manage future outbreaks.

Aeration and Dethatching Tips

Healthy lawns start from the ground up. Over time, Zoysia grass can develop a layer of thatch, which is a thick layer of dead roots and stem tissue located between the grass and soil. Overly dense thatch can hold moisture and encourage disease. Here’s how to manage it:

• Aeration: Penetrating the soil allows better drainage and permits air, water and nutrients to reach the roots. Do this no more than once a year, in late spring or early summer.

• Dethatching: Anxious to get a frothy froth on? Use a mechanical dethatch rake or a power dethatcher and remove the mat thatch. If the thatch is more than ½-inch thick, it’s time to do something.

• Compost after dethatching: Compost can be lightly applied to help feed the soil and promote good regrowth.

Healthy soil equals healthy grass and fewer diseases.

Zoysia Grass Disease Prevention

Proper Watering Techniques

Fungus thrives on too much water. Zoysia does not require as much watering as you might think. Here is how to become a pro at watering:

• Water deep but infrequently: Provide the lawn with 1 inch of water a week to include rainfall.

• The morning works best: Water from 6 a.m. to 10 a.m. so that the grass will dry out in the day.

• Do not water in the evening: It results in cool, damp conditions, perfect for fungal growth.

• Measure how much water is landing on your lawn each time with a rain gauge or tuna can.

Ideal Mowing Practices

It seems like such an easy task, but mowing incorrectly can leave your grass plant open to stress and disease. Follow these tips:

• Sharpen your mower blades: Dull blades rip the grass, producing wounds that allow disease in.

• Don’t trim too much: Keep Zoysia at 1.5 to 2.5 inches. Cutting too low weakens it.

• Mow at the correct time of day: Wet mowing helps to spread disease and can tear the grass.

• Leave clippings: As long as they’re not clumping or diseased, clippings release nutrients to the soil.

• Frequent: light mowing keeps the lawn healthy and robust.

Fertilization Tips

Properly fertilizing Zoysia helps to keep it vigorous and resistant to diseases. “But if there’s too much or too little, you can shoot yourself in the foot.” Here’s what you need to know

• First, test your soil: Know what your lawn really needs in the way of nutrients.

• Apply nitrogen: Use a slow-release fertilizer in early summer. Do not apply excessive nitrogen in the fall.

• Don’t overdo it: Too much fertilizer results in fast, weak growth fungi thrive on.

Apply a properly balanced fertilizer (such as 16-4-8) according to soil test recommendations.

Best Seasonal Care

The needs are different every season. Follow this seasonal routine:

• Spring: Trim or rake to remove debris and use a leaf blower on garden beds, carefully using a rake to break apart and remove any matting or dead grass that might be killing your lawn (or preventing it from growing). 

• Summer: Practice water wisdom, mow frequently and check for pests or disease.

• Autumn: Water less, dethatch if necessary, and refrain from fertilizing late in the year.

• Winter: Zoysia goes dormant give it a break. Do not fertilize and keep foot traffic away.

Keep ahead of unhealthy by matching your lawn care schedule with the seasons.

Conclusion

Zoysia grass can be the turf of everyone’s dreams, but only if it’s healthy. Knowing the causes, symptoms and treatments of common Zoysia grass diseases puts you a step ahead. Whether it is large patch, rust or decline leaving damage in its wake, early identification and regular care can help prevent it.

Water judiciously, mow properly, fertilize sensibly, and aerate periodically. And if things head south, get out the right fungicides and don’t be afraid to call in the pros.

The secret to a lush Zoysia lawn is plenty of balance, a good deal of patience, and a little bit of know when to show when to go.

FAQs

How often should I treat my Zoysia for disease?

Treat only in the presence of disease or highly conducive conditions for growth of the fungus. Fungicides can be overused and cause resistance and harm beneficial soil organisms.

What is the best fungicide for Zoysia grass?

Fungicides with either Azoxystrobin, Propiconazole, or Myclobutanil work well for common diseases such as large patch and leaf spot. Rotate items so resistance doesn’t develop.

Can I resurrect dead Zoysia grass?

(If the roots remain alive, the answer is yes.) Improve soil conditions, water deep, dethatch, and reseed or plug bare spots if necessary.

Should I dethatch every year?

Not necessarily. Only dethatch if the layer of thatch is over ½ inch thick. Once a year aeration does more for the health of your turf.

Is Zoysia more resistant to disease than Bermuda?

Zoysia tends to have slightly better disease resistance and drought tolerance than Bermuda, but both require proper care to avoid issues.