1/9/2024

Pythium blight, also known as “grease spot” or “cottony blight,” can wreak havoc on golf courses, leaving behind large, dead areas that are an eyesore for golfers and a nightmare for maintenance crews.  

In this article, we will uncover the causes, symptoms, and, most importantly, the proven strategies to combat Pythium blight. Whether you're a seasoned golf course professional or a novice greenkeeper, our expert tips and techniques will equip you with the knowledge and tools you need to control this devastating disease.  

What is Pythium Blight? 

Pythium blight is caused by the pathogen Pythium aphanidermatum, a fungal-like organism in the oomycete kingdom. It is well known for attacking and killing many different plant species including turfgrasses found on lawns, athletic fields, and golf courses.   

The disease thrives in warm, wet, and humid conditions, making it particularly problematic in regions with hot summers, and leads to unsightly areas of tan or brownish, dead grass.  

Pythium blight is most prevalent on golf courses with poorly draining soils or excessive thatch build-up. The disease spreads rapidly, especially during extended periods of high humidity, excessive rainfall, or after a heavy snowmelt. Therefore, understanding the prime conditions for and early signs of Pythium blight can help prevent its spread and minimize its impact on high-value stands and playing surfaces. 

Identifying Pythium Blight 

Often identifiable by active mycelia that appear purplish gray or white and cottony, Pythium blight can be observed in the early morning or during periods of high moisture. The disease usually starts as small, reddish-brown spots with infected leaf blades appearing water-soaked or slimy in the morning dew.

If hot, humid conditions persist, the disease progresses into irregular patches of damage, often becoming more pronounced. These patches can quickly expand, “track,” or streak with mowing patterns or surface water drainage, leading to widespread damage if left untreated. Early detection and prompt action are crucial in effectively managing Pythium blight and minimizing its impact on aesthetics and playability. 

Factors That Contribute to Pythium Blight 

Several factors contribute to the development and spread of Pythium blight on golf courses. Understanding these factors is essential in implementing effective preventative measures and treatment strategies.  

High soil moisture, especially combined with warm temperatures, creates the ideal environment for Pythium blight to thrive. Poor drainage or compacted soils exacerbate this problem by retaining excess water and promoting prolonged leaf wetness. Golf courses with excessive thatch are also more susceptible to Pythium blight, as thatch provides a favorable habitat for Pythium spores, allowing them to survive and infect the turfgrass. Additionally, cultural practices such as over-irrigation and inadequate air circulation can contribute to the development and spread of Pythium blight.  

Lastly, the introduction of Pythium-infected plant material or contaminated equipment can introduce the disease to previously unaffected areas of the golf course. By identifying and addressing these contributing factors, golf course professionals can significantly reduce the risk of Pythium blight outbreaks.

Preventative Cultural Measures for Pythium Blight 

Prevention is the first line of defense against Pythium blight on golf courses. Implementing proactive measures can help minimize the risk of disease development and reduce the need for intensive treatment.  

First, a balanced approach to turfgrass management is essential in preventing Pythium blight and other damaging diseases. The use of excessive nitrogen fertilizer during periods of hot, humid weather, especially in the absence of balanced nutrition, can weaken the turfgrass and make it more susceptible to disease. Instead, employing a controlled-release fertilizer like POLYON® allows for more consistent and predictable nutritional feeding. Additionally, it is important to maintain proper soil pH and to avoid mineral deficiencies.

Proper irrigation management is crucial in preventing Pythium blight. Avoid over-watering, especially during periods of high humidity or when the weather forecast predicts prolonged rainfall. Regular monitoring of soil moisture levels can help ensure that irrigation practices are optimized for the specific needs of the turfgrass species. 

Improving soil drainage is another critical preventative measure. Cultivation practices such as venting, coring, or deep tining to alleviate compaction and promote air/water movement can significantly reduce the risk of Pythium blight. Golf courses with excessively compacted soils may benefit from the installation of drainage systems or the incorporation of sand-based topdressing materials to improve water infiltration.  

Finally, it is also essential to address thatch accumulation through regular verticutting or dethatching to minimize the potential for Pythium and other fungal diseases that thrive in excessive organic matter accumulation. 

Chemical Treatments for Pythium Blight 

Fungicides are the primary means of chemical control for Pythium blight. When selecting a fungicide, choosing products specifically labeled for use on golf course turfgrass is crucial. Fungicides containing active ingredients such as propamocarb, Cyazofamid, mefenoxam, strobilurin chemistries, or potassium phosphite have been shown to control or suppress Pythium blight effectively.  

In some cases where Pythium is a chronic issue, resistance to fungicides can be a concern. It's important to consider rotating chemistry using a programmatic approach with different modes of action to keep populations in check. Harrell's has some excellent reference tools and fungicide program recommendations that can help with product selection and application timing. Our programs rotate through best-in-class products from top-tier industry manufacturers like Envu, Syngenta, BASF, FMC, Nufarm, and others. To get a copy of the program for your region, reach out to a Harrell's Rep or find our free fungicide guide poster here.

Top performing solutions include: 

1.                   ProtectMAX® Cyazo

2.                   Subdue Maxx®

3.                   Banol

4.                   ProtectMAX Title Phyte®

With the active ingredient Cyazofamid, Harrell’s ProtectMAX® Cyazo is the industry-leading preventive and curative Pythium control option in an SC formulation with excellent tank mix compatibility. The product offers familiar use rates and is labeled for golf courses, sod farms, residential lawns and landscapes, professional and collegiate athletic fields, ornamentals in landscapes, greenhouses, and nurseries. 

How Harrell’s ProtectMAX® Cyazo Works 

Cyazofamid works within the inner mitochondrial membrane's respiratory system. As the “powerhouse” of the cell, this generates energy (ATP)​. Cyazo interrupts the respiration chain and halts the growth and development of many different Pythium species and other plant pathogenic oomycetes as well.  

Cyazofamid is in the FRAC 21 class of fungicides. It enters plant tissues and accumulates in the waxy cuticle. With translaminar movement, it can suppress existing infections (curative use)​. 

ProtectMAX® Cyazo is labeled to control turf diseases, including Pythium blight, Pythium damping off, Pythium root rot, and Pythium dysfunction. On ornamentals, ProtectMAX ® Cyazo controls Pythium crown, Pythium root rot, Pythium damping off, Phytophthora crown, root rot, and foliar blight, as well as downy mildew. 

Proper application timing and rates are critical for maximizing fungicide efficacy. Consult with your Harrell’s rep to determine the most appropriate fungicide and application schedule for your specific golf course conditions and agronomic situation. 



Best Practices for Managing Pythium Blight on Golf Courses 

It is important to remember that Pythium blight management is an ongoing process that requires consistent monitoring and adaptation to changing environmental conditions. 

Regular communication and collaboration with your Harrell’s rep and Harrell’s Directors of Agronomy can provide valuable insights and support in managing Pythium blight.  

Reach out to your Harrell's Rep to discuss combatting Pythium and how Harrell’s ProtectMAX® Cyazo can work for you.