Dealing With Turf Disease

On Feb 5, 2025  91

The most common fungal disease found on UK bowling greens is probably fusarium patch and this autumn and early winter period has been one of the worst for outbreaks of Fusarium for some time (writes John Quinn, our Greencraft expert). Much of the work you have to do to minimise your green’s susceptibility to fungal diseases is just sound greenkeeping and very rarely relies on magic or expensive solutions. The majority of the work required to produce a great bowling green is physical and not chemical. Anyway, back to fungal diseases; they can be devastating to your green and can result in most or all of the turf being killed, if left unchecked. The danger time is largely the winter months and unfortunately this is when the green is likely to get the least attention. For illustration if you only inspect the green once a week during winter, you could conceivably come back to a green devastated by fusarium which wasn’t even visible to the layman on the previous visit.

Why is it a problem?

As you can see from the photo of fusarium above, this disease can completely wipe out the turf on your green if left un-checked. Although the green will recover in most cases, the surface will be un-even for a long time afterwards and a lot of the finer grass will be lost to be replaced by annual meadow grass. This is part of the fine turf circle of decline we have discussed in other articles.

What can I do about it?

Of course, in the thick of an attack of fusarium it is too late to think about prevention and you want to stop the spread of the disease as soon as possible and traditionally that has meant applying a fungicide. However, most turf fungicides fall into the category of broad spectrum fungicides, meaning that they kill most fungi. Furthermore, many bowling greenkeepers don’t hold certification to legally apply these…and of course they can be very expensive.

PotSi: Research has shown that Silicon plays a crucial role in strengthening cell walls, which is vital for turfgrass resilience against various biotic stresses like insect pests (leatherjackets and chafers) and fungal diseases. Silicon is deposited as amorphous silica within the cell walls, increasing their rigidity and making it more difficult for pathogens to penetrate. For instance, studies have demonstrated that Silicon-treated plants show reduced susceptibility to fungal infections such as Dollar Spot and Fusarium, which are increasingly common problems in fine turf. Regular applications of PotSi are cheap, non-pesticidal and can greatly reduce fungal disease outbreaks and an added application at the first sign of an outbreak of disease will elicit a strong immune response from plants. A key point to remember here is that all fungal diseases that affect turf are largely attracted and encouraged by the same short list of factors; namely excessive thatch, compaction, excess surface water (thatch and compaction again), grass being left too long in winter, mild weather, leaf cover, snow cover, obstructed airflow over the turf etc. So again, it is important to look after the basics of fine turf management to help you to minimise the likelihood of an outbreak of disease. This means all the same old stuff as before; thatch management, compaction relief and control, nutrition management, irrigation management and just making sure that all of the regular physical activities are done on time and regularly.

The Disease Triangle

The disease triangle is a fundamental concept in plant pathology that explains the interaction of three critical factors required for disease development: 1. Host 2. Pathogen 3. Environment When applied to turfgrass diseases like fusarium patch (caused by Microdochium nivale), the triangle provides a framework to understand and manage disease susceptibility.

Here’s a detailed breakdown:

1. Host: The Grass Plant: The host refers to the turfgrass species or cultivar. Some grass types are inherently more resistant to Fusarium Disease, while others are more susceptible. Factors influencing host susceptibility include: • Species and Variety: ◦ Fescues tend to be more resistant than perennial ryegrass or annual meadowgrass (Poa annua), which are highly susceptible. • Nutritional Status: ◦ Over-fertilisation with nitrogen (especially late in the growing season) can lead to lush, soft growth that is more susceptible to fungal infection. ◦ Poor nutrient levels can weaken the grass, reducing its ability to fend off infection. • Turf Health: ◦ Stressed turf (from mowing, compaction, or drought) has lower resistance to diseases. ◦ Dense thatch layers can harbour pathogens and promote infection.

2. Pathogen: Fusarium: The pathogen must be present for the disease to occur. Key characteristics of Fusarium Disease include: • Survival: ◦ The pathogen can survive as mycelium or spores in plant debris, thatch, or soil. ◦ In cool, damp conditions, it can rapidly proliferate. • Infectivity: ◦ Fungal spores can germinate and infect leaf tissue under favourable environmental conditions. Microdochium nivale thrives in temperatures between 0-8°C (cool-season fungus) but can remain active even outside this range if moisture is abundant.

3. Environment: Conditions for Disease Development: Environmental conditions often act as the trigger for fusarium outbreaks. Critical environmental factors include: • Moisture: ◦ Prolonged leaf wetness from dew, rain, or poor drainage creates an ideal environment for fungal spore germination. • Temperature: ◦ Fusarium patch is most active in the cooler months (autumn to early spring), particularly when temperatures are in the range of 0–15°C. • Light Levels: ◦ Reduced sunlight (shorter days and shaded areas) increases surface wetness duration, favouring disease. • Poor Airflow: ◦ Stagnant air reduces drying of leaf surfaces, encouraging fungal development. • Management Practices: ◦ Practices such as late-season nitrogen application, excessive irrigation, and scalping during mowing can exacerbate environmental conditions conducive to infection.

The Disease Triangle Applied: Fusarium Patch

For fusarium patch to develop, all three factors—susceptible host, pathogen presence, and favourable environment—must overlap: • Susceptible Host: Lush annual meadowgrass dominated swards, over-fertilised turf with lush growth. Too much Nitrogen applied late in the season • Pathogen Presence: Residual spores in thatch or soil. • Favourable Environment: Cool, damp, and overcast conditions with extended leaf wetness. Poorly aerated or drained soil, excessive thatch build up holding water at the surface. Debris on surface creating a microclimate for spores to thrive in, such as leaf little, worm casts, dew or even long grass. If one of these factors is removed or minimised, the disease cannot occur or will be less severe. For example: • Reducing thatch (host) lowers pathogen harbouring areas. • Avoiding excessive nitrogen discourages soft growth (host). • Improving drainage or dew removal (environment) limits moisture availability.

Practical Implications for Greenkeeping

• Cultural Practices: ◦ Aerate soil to improve drainage and airflow. ◦ Scarify or verticut to reduce thatch in autumn ◦ Use dew removal techniques (e.g., switching and/or brushing). • Nutritional Management: ◦ Avoid high nitrogen fertilisers late in the season. ◦ Apply balanced nutrients to maintain turf health (e.g., low N, high K). • Preventive Measures: ◦ Use fungicides sparingly and responsibly as part of an integrated management plan. ◦ Consider resistant grass cultivars when reseeding or establishing new greens. By managing one or more sides of the disease triangle, the severity of fusarium patch can be reduced significantly. Here to help I’ve been helping clubs to move to a more sustainable and less complex approach to greenkeeping for many years and I am always ready to help anyone who would like to learn more about this path to better bowling greenkeeping for the future.