How to Treat Pythium Root Rot in Your Lawn

Pythium Root Rot is caused by several different Pythium pathogens and is most likely to strike already stressed or excessively damp lawns. It’s a fast acting disease and can devastate home lawns within just a few days, so it’s important to be vigilant and act fast if you suspect your lawn to be under disease stress. Alternatively, you can strike pre-emptively if you’ve noticed the weather conditions that could spike a Pythium outbreak.

What are the Symptoms of Pythium Root Rot in Your Lawn?

Pythium Root Rot will initially manifest as discoloured circular patches in the lawn, typically between 2-5cm but can be as large as 15cm. If you feel the leaves of the affected plant you might notice that they’re slimy to touch, and as the disease progresses and inflicts more damage on the plant these slightly discoloured patches will get gradually darker brown as the days go by.

Pythium Root Rot festers in well watered lawns and humid climates, so it’s not uncommon to wreak havoc on lawns that have been renovated late in Spring or Early Summer that would be receiving more water than usual.

It’s also common in regions that are receiving higher than average Summer rainfall or dry areas experiencing high Summer temperatures, and over-compensating for heat stress by over-watering their home lawns.

Pythium is present in all soil types and flourishes in waterlogged soils. Compacted or poor draining soils can increase the chance of a Pythium outbreak as well-intentioned lawn lovers will typically overwater these soil types in an effort to relieve moisture stress from their lawn.

What Turf Types are Prone to Pythium Root Rot?

Pythium Root Rot affects all warm season grasses including Couch/Bermuda Grass, Buffalo, Kikuyu and Zoysia, but can also affect cool season grasses like Rye, Kentucky Blue Grass, Fescue or Bent Grass.

While Pythium Blight and Pythium Root Rot are both caused by Pythium fungi, they are not the same condition. The key difference lies in the stage of the root damage and environmental triggers.

Pythium Blight affects the leaves of the plant and can leave them feeling greasy or covered in white patches that look like a spider’s web early in the morning. Pythium Blight is devastating to the leaves and can cause mild discolouration or even the death of the entire leaf.

Pythium Root Rot, on the other hand, is far more aggressive. It typically occurs in waterlogged or overly saturated soils, where roots become smothered and quickly begin to rot. Pythium Root Rot causes rapid turf decline and is often associated with heavy rains, poor drainage, or irrigation issues.

While Pythium Root Rot can be a devastating affliction, there are several easy cultivation changes that can lessen your chance of a Pythium outbreak, as well as commercially available fungicides that will treat the ailment quickly.

Prevention and Control

1. Improve Drainage and Aeration
   • Reduce soil compaction by aerating your lawn annually, which improves air and water movement in the soil.
   • Address poor drainage areas to prevent prolonged moisture in the root zone.
     
2. Manage Watering Carefully
   • Water deeply but infrequently to encourage deep root growth and avoid constantly wet conditions.
   • Water early in the morning to allow the lawn to dry throughout the day.
3. Monitor Thatch Levels
   • Excess thatch traps moisture and creates the ideal environment for Pythium fungi. Regular dethatching (sometimes referred to as vertimowing, grooming or scarifying) can help keep thatch under control.
4. Nutrient Management
   • Avoid excessive nitrogen fertilisers, as they can promote lush, weak growth that is more susceptible to disease. Use a balanced fertiliser to maintain healthy, resilient turf.

Treatment Methods

Few domestically available fungicides are registered to control. The most commonly available would be Impala. The rates for application are on the bottle, but most ailments can be treated at a rate of 60mL/100sq.m of lawn. Be sure to apply as per the label’s instructions, and by using correct protective equipment.

Pythium Root Rot can come on quickly during wet Australian summers or in regions battling above average rainfall and warmer weather, but fortunately this potentially devastating lawn disease can be stopped in its tracks by some cultivation practices and easily accessible lawn fungicides. Visit myhomeTURF’s online store for a wide selections of fungicides for your lawn care.