Turf diseases - identification and treatment

Author: Stefan Palm   Date Posted: 12 December 2023 

With the uncharacteristic combination of wet, warm and humid conditions present in South Australia at the moment, lawn disease is a realistic possibility for your lawn.

As the sun's rays intensify and temperatures climb, your lush green lawn can become a battleground for survival. Summer brings with it not only the challenge of scorching heat but also the lurking threat of various lawn diseases that can turn your pristine yard into a patchwork of brown and yellow patches.

In this blog, I’ll mention some of the most common lawn diseases that rear their heads during the summer months and discuss effective strategies to keep your lawn healthy and vibrant.

What are they, and what do they look like?

For the record, the most common types of turf diseases in South Australia include:

  • Helminthosporium
  • Rhizoctonia
  • Electrophic root-infecting fungi (ERI)
  • Fusarium
  • Anthracnose
  • Dollar Spot

While there are distinctive differences between different types of lawn diseases, to the untrained eye, they will present as dead and dying patches in your lawn.  These patches can range from small spots on your lawn, to dinner plate size patches through to patches nearly as big as your lawn. You may only have a few patches, or you may have many of them.

For home gardeners, it is next to impossible to accurately diagnose particular types of diseases or, in fact, even turf disease in general, making treatment challenging.

Where do they come from / what are the causes?

Lawn diseases are typically caused by various types of pathogens, including fungi, bacteria, viruses, and nematodes. These microorganisms can be introduced to your lawn through a variety of means, and their development is often influenced by environmental conditions. Here are common sources and factors contributing to the emergence of lawn diseases:

How they are introduced:

  • Most diseases are introduced via airborne spores. These spores can be carried by the wind, from infected plants or lawns to healthy ones, leading to the rapid spread of diseases.

Environmental Conditions:

  • Moisture: Many lawn diseases thrive in moist conditions. Overwatering or poorly drained soil can create an environment conducive to the development of fungal and bacterial diseases.
  • Watering your lawn at night can lead to it remaining wet or moist for extended periods. If the weather is warm, a humid microenvironment can be created in the thatch of your lawn, providing ideal conditions for pathogens to grow.
  • Temperature: Different diseases have specific temperature ranges in which they thrive. Most diseases are more prevalent in the warm summer months.  

Soil Conditions:

  • Compacted soil limits root growth and reduces air circulation, creating conditions favourable for certain diseases. Regular aeration helps alleviate soil compaction.
  • Poor soil health, including imbalances in nutrient levels, can weaken grass and make it more susceptible to diseases. Proper fertilisation helps maintain a healthy lawn.

Key factors in determining if it is disease.

I mentioned earlier that it's difficult for home gardeners to diagnose lawn diseases. Since disease presents as dead and dying patches in your lawn, disease is often mistaken for other lawn problems that also present as dead and dying patches. In fact, just about all problems in lawns present as dead and dying patches so you can see how difficult it can start to get to identify disease. It’s also worth mentioning here that disease is generally less common than other problems that can affect your lawn, so it shouldn’t necessarily be the first thing you jump to.

There are, however, some consistent themes that should raise suspicions when determining whether disease has infiltrated your lawn:

  • Lawn diseases generally come on very quickly. In many cases, overnight. Your lawn can look good one day and then be covered in patches the next.
  • Lawn diseases generally don’t persist for months and years. If you have long-standing dead and dying patches, it may be something else.
  • Lawn diseases generally don’t attack the same areas year after year. If you have a patch that dies off in the same area at the same time each year, it may be something else.  

How to diagnose and treat lawn diseases

Prevention is the Best Medicine. It's definitely worth spending some time considering how to create the least favourable conditions for diseases to spread. Below are some tips:

  • Well-Timed Watering: Water consistently during the summer months – around 25mm per week is ideal, either by rain or sprinklers. Water early in the morning to allow the grass to dry during the day. Watering at night is a key contributor to encouraging disease.
  • Aeration: Regularly aerate your lawn to improve soil compaction and enhance air circulation, reducing the risk of diseases like summer patch and thatch buildup.
  • Balanced Fertilisation: Apply fertiliser at regular intervals during the year to keep your lawn healthy. A balanced nutrient profile strengthens the grass and helps it resist diseases.
  • Manage Thatch: Thatch buildup creates a breeding ground for diseases and pests. Regular dethatching prevents this layer from becoming a haven for pathogens.

If you are doing all of this and still manage to get a breakout of patches in your lawn, enlist the help of a lawn specialist for advice. Soil samples, lawn samples and photographs can all be helpful in diagnosing problems. The most comprehensive way of determining if you have disease issues is to have a soil and plant tissue analysis done in a lab environment. This can be arranged for about $150 and will provide you with a comprehensive report and treatment plan.

Alternatively, you can spray your lawn with a broad spectrum, trans-laminar fungicide such as Tombstone; however, this should not be done lightly. Improper use of fungicides like this can lead to resistant populations of pathogens that become much harder to control in the long term.

A thriving lawn requires a proactive and informed approach to disease prevention and treatment. By implementing the right practices, promptly identifying issues, and taking appropriate remedial measures, you can enjoy a lush and disease-free lawn throughout the seasons.

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