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Turf disease has always been a consistent adversary across the United States for residential lawns and commercial landscapes alike. With the arrival of summer comes the looming threat of lawn disease outbreaks in cool season grasses.

Though disease outbreaks can occur in warm season turf, it usually happens during the spring and fall months as temperatures shift between winter and spring, or fall and winter. Cool season grasses are more commonly impacted by disease during the summer months (mid-June) and into the early fall. Common diseases found in cool season turf: include brown patch; large patch; Pythium blight (seen below); spring dead spot; and fairy ring.

lawn disease

In addition to chemical fungicide solutions with the ability to cure turf disease, there are cultural methods that help prevent disease outbreaks. Shown here is Pythium blight on turf. (Photo: Sod Solutions)

 

Although certain chemical fungicide solutions have the ability to cure turf disease, there are a few cultural methods that can be performed to keep disease outbreaks from occurring beforehand.

Mowing. Mowing grass at its recommended mowing height improves turf’s ability to fight off disease. When mowing, no more than one-third of the leaf blade should be removed at all times. Removing more than this amount increases the possibility for disease outbreaks since the grass will have a difficult time recovering from stress or damage.

Regular maintenance on mowers also ensures a sharpened mower blade for proper cutting. Mowing with dull blades increases the chance of disease as the mower blades tear the grass instead of neatly slicing them. Once the grass is ripped, it is left open and vulnerable to disease access.

Irrigation. Although turf requires a certain amount of water, the amount of times it’s watered each week greatly depends on how long the system can run before creating puddles or run-off. A good way to see how much water the grass is receiving at various locations is by conducting an irrigation audit.

Start by placing several cups around the landscape that will capture the amount of water delivered to each zone during a single irrigation cycle. The goal is to consistently collect half a ½” of water in the cup for each zone. One inch of water within the week is usually enough depending on the grass type, so a ½” delivered twice a week will meet this requirement. Adjustments to the irrigation cycle can be made once water has been collected.

Overwatering creates water-logged soils, which are ideal environments for disease outbreaks. Provide turf with the proper amount of water required on a weekly basis.

Fertilization. Although nitrogen applications may seem counterproductive when disease is present, regularly applying the appropriate amount of fertilizer promotes a healthy, dense canopy with exceptional disease resistance before disease outbreaks occur. There is a balance when it comes to fertilizer applications though—applying fertilizers with too much nitrogen, especially in a fast-release form, encourages unnecessary growth in the leaf blades. This provides more opportunities for fungal penetration. Collecting and submitting a soil analysis provides information about which nutrients are currently present in the soil and which nutrients are absent. This helps to provide helpful information to select a fertilizer that fits the soil’s needs and prevent unnecessary nitrogen applications. The healthier the turf grass is, the more capable it will be at fighting off disease and recovering.

Soil Aeration and Thatch Removal. Aerating landscapes reduces soil compaction and thus provides more room for roots to expand and deepen into the soil. This in turn increases the grass’s ability to recover from damage and decreases the likelihood of disease, or even insect invasions. It also permits access to an increased amount of oxygen, water, and other beneficial nutrients for the grass. Aeration should be performed during the spring and fall for cool season grasses.

While ½” of thatch actually provides benefits to grass like warmth for roots or a reduction in water evaporation. Too much thatch is an optimal environment for certain diseases like fairy ring, gray leaf spot, or summer patch. Thatch removal in cool season grass in the late summer or early fall is a great prevention strategy.

Compost Application. Organic composts applied to lawns have been successfully used to suppress diseases and are becoming more popular. The best starting materials for organic composts consist of manures, food, lawn wastes, or even sewage sludges. Organic composts also help soils break down chemicals faster than soils without compost applications. Although composts made up of sands or sphagnum peat are more commonly used, especially among golf and sports industry professionals, they are less suppressive materials for composts.

Irrigation. Although turf requires a certain amount of water, the amount of times it’s watered each week greatly depends on how long the system can run before creating puddles or run-off. A good way to see how much water the grass is receiving at various locations is by conducting an irrigation audit.

Start by placing several cups around the landscape that will capture the amount of water delivered to each zone during a single irrigation cycle. The goal is to consistently collect half a ½” of water in the cup for each zone. One inch of water within the week is usually enough depending on the grass type, so a ½” delivered twice a week will meet this requirement. Adjustments to the irrigation cycle can be made once water has been collected.

Overwatering creates water-logged soils, which are ideal environments for disease outbreaks. Provide turf with the proper amount of water required on a weekly basis.

Fertilization. Although nitrogen applications may seem counterproductive when disease is present, regularly applying the appropriate amount of fertilizer promotes a healthy, dense canopy with exceptional disease resistance before disease outbreaks occur. There is a balance when it comes to fertilizer applications though—applying fertilizers with too much nitrogen, especially in a fast-release form, encourages unnecessary growth in the leaf blades. This provides more opportunities for fungal penetration. Collecting and submitting a soil analysis provides information about which nutrients are currently present in the soil and which nutrients are absent. This helps to provide helpful information to select a fertilizer that fits the soil’s needs and prevent unnecessary nitrogen applications. The healthier the turf grass is, the more capable it will be at fighting off disease and recovering.

lawn disease

Overwatering creates water-logged soils, which are ideal environments for disease outbreaks. Provide turf with the proper amount of water required on a weekly basis.


lawn disease

Shown here is brown patch, a common disease found in cool season grasses. (Photos: Sod Solutions)

Soil Aeration and Thatch Removal. Aerating landscapes reduces soil compaction and thus provides more room for roots to expand and deepen into the soil. This in turn increases the grass’s ability to recover from damage and decreases the likelihood of disease, or even insect invasions. It also permits access to an increased amount of oxygen, water, and other beneficial nutrients for the grass. Aeration should be performed during the spring and fall for cool season grasses.

While ½” of thatch actually provides benefits to grass like warmth for roots or a reduction in water evaporation. Too much thatch is an optimal environment for certain diseases like fairy ring, gray leaf spot, or summer patch. Thatch removal in cool season grass in the late summer or early fall is a great prevention strategy.

Compost Application. Organic composts applied to lawns have been successfully used to suppress diseases and are becoming more popular. The best starting materials for organic composts consist of manures, food, lawn wastes, or even sewage sludges. Organic composts also help soils break down chemicals faster than soils without compost applications. Although composts made up of sands or sphagnum peat are more commonly used, especially among golf and sports industry professionals, they are less suppressive materials for composts.

Systemic Chemical Solutions

Cultural methods aren’t always sufficient for disease prevention or treatment. Landscapes that experience a higher level of disease outbreaks may need preventive applications of a systemic fungicide. If a disease outbreak is present, it usually displays itself in a circular or irregular pattern of damage. As mentioned at the start of this article, common diseases found in cool season turf include: brown patch (shown here); large patch; Pythium blight; spring dead spot; and fairy ring. One of the best methods for overall disease treatment is to apply a systemic fungicide at a curative rate. Systemic fungicides with active ingredients like azoxystrobin (Heritage) or triadimefon serve as penetrants that are absorbed into the system of the plant and eliminate disease so that the plant can restore itself back to health.

Diseases in cool season grass typically develop when temperatures increase or when excessive rainfall occurs. When the two are combined, an ideal environment for disease outbreaks is created.

Valerie Smith, Sod SolutionsSmith is a digital content specialist with Sod Solutions, Inc. Based in the Charleston, SC area, Sod Solutions has helped to develop and release more than 20 turfgrass varieties to the market over the past 27 years including Palmetto® and CitraBlue® St. Augustine, EMPIRE® and InnovationTM Zoysia and Celebration®, Latitude 36® and NorthBridge® Bermudagrass. The company’s team of experts offers professional insight about turfgrass disease and fungicide products.

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