Bank on Pythium when the weather gets hot

It’s time to protect against Pythium diseases when the hot, humid, dogdays of summer are in the forecast.

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For a long time Pythium diseases in turf weren’t well understood. Previously golf course superintendents often blamed dead turf in mid-summer on general summer decline, but in reality were suffering from undiagnosed Pythium issues. Our understanding of Pythium diseases has improved significantly through research over the past 20 years. The turf industry is better at identifying the true culprit causing turf to die or struggle… and has found ways to fight back.

Pythium is a big tent covering multiple turf diseases that can occur all throughout the growing season. Contrary to what many may think, Pythium are not true fungi and is why most conventional turf fungicides prove ineffective in controlling Pythium diseases. They are actually classified as Oomycetes, organisms more closely related to brown algae than fungi, and are primarily decomposers of organic matter in soil. However, under certain conditions, Pythium can become plant pathogens causing destructive diseases.

Oomycetes such as Pythium are often called water molds, which is helpful in understanding the environmental conditions in which they thrive. Pythium doesn’t do well without ample freely available water. The one common weapon against all Pythium diseases – whether it’s foliar blight or root rot – is improving subsurface and surface drainage and airflow.

Pythium foliar blight

Pythium foliar blight, caused by Pythium aphanidermatum, thrives in hot, humid days when it doesn’t seem to cool down that much at night. Daytime temperatures above 28 °C and nighttime temperatures that don’t drop below 20 °C are the perfect breeding ground for Pythium. Combine that with high relative humidity and long periods of leaf wetness and the disease really starts to take off.

The disease appears as sunken, water-soaked patches and streaks on turf that can take on an orange to dark grey colour. Affected turf is often matted and will turn straw brown and shriveled under dry conditions. Cottony flocks of mycelium can also be found on the turf when the disease is active, usually during periods of heavy dew in early morning.

Planning a preventive fungicide application when hot, humid temperatures are in the forecast is the best strategy for protection against Pythium foliar blight. Curative control once Pythium foliar blight strikes can often be inneffective because the disease moves so quickly that within a couple of days the damage is done, leaving very little time to spray. You have to get out ahead of Pythium foliar blight.

Pythium root rot

There are over 40 different Pythium species that have been documented to cause Pythium root rot. Each of these species can thrive under different temperature ranges but the main driving factor for all of them is high soil moisture in the rootzone.

Pythium root rot can rear its head almost anytime through the season. Pay special attention to native soil putting greens and low-lying areas with bad drainage where water ponds. High-traffic areas that are compacted are also at risk.

Pythium root rot can be difficult to diagnose just looking at turf symptoms. Irregular areas of declining and chlorotic turf aboveground can be an indicator of Pythium root diseases causing havoc underground. Roots suffering from Pythium root rot are often tan in color, necrotic, and are shorter in length than surrounding turf. Microscopic examination of roots is needed to accurately confirm diagnosis.

Once you identify Pythium root rot you can get on a regular, preventive program that includes improving drainage and airflow and the use of a preventive fungicide before hot weather hits. Banol® has reliable preventive and curative activity on Pythium root rot when watered into the rootzone.


Pythium root disfunction

Pythium root disfunction is primarily associated with creeping bentgrass on sand-based putting greens and is caused typically by a single species, Pythium volutum. High moisture in the root zone allows for infection of the roots during the spring and fall shoulder seasons at soil temperatures between 10 and 24 °C. However, symptoms of the disease may not show up until you hit the heat of the summer. The lack of functioning roots results in the plant not being able to draw in water and nutrients properly, allowing aboveground symptoms of the disease to show up in periods of drought and extreme heat.

To effectively control Pythium root dysfunction, preventative control measures need to happen in spring and fall when the pathogen is active in the soil. Those measures include preventative fungicide applications and improving soil drainage and airflow.

Damping off

New plantings and turf in the seedling stage are at risk of damping off, another disease caused by Pythium. The disease thrives under wet conditions that are typical in new turf plantings and can quickly wipe out weak seedlings. Turf that is affected by damping off rarely recovers and reseeding of the areas will need to be performed. Applying a preventative fungicide to these areas during early establishment is recommended to protect seedlings.

Controlling Pythium

Pythium is best controlled through a preventative fungicide program combined with effective cultural practices that improve drainage and airflow. If you wait until you see symptoms of these diseases, the turf might already be weakened to the point that it can’t withstand other stresses.

Signature XTRA Stressgard® provides strong preventive activity against Pythium diseases. Since it is fully systemic, there is no need to water in applications and provides protection from Pythium foliar and root diseases. Signature XTRA Stressgard also activates plant defenses, has unique Stressgard Formulation Technology, and should be used as part of a seasonal disease control and plant health program.

Banol® has reliable preventive and curative activity against Pythium diseases. For Pythium foliar blight, applications should target complete coverage of the foilage. For Pythium root diseases, Banol should be watered into the rootzone for root uptake to be most effective.

Utilizing Signature XTRA Stressgard and Banol separately or in combination are excellent solutions in providing ultimate Pythium protection during the toughest stetches of the growing season.

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Bayer, the Bayer Cross, Banol®, Signature XTRA Stressgard® and Stressgard® Formulation Technology are trademarks of Bayer Group. Used under license. Bayer CropScience Inc. is a member of CropLife Canada. ©2022 Bayer Group. All rights reserved.