We are now entering the time of the year when we are likely to see the formation of morning dews on our grass surfaces. This generally occurs when evening air temperatures start dropping dramatically, especially when we have clear cloudless nights.

On a clear day, water evaporates from the warm ground into the atmosphere. When night falls, the ground radiates the day's warmth into the skies. Warm air can hold more moisture which precipitates out onto the leaf as the temperatures plummet overnight. The ground becomes much cooler, causing the water vapour to condense. This condensed vapour is dew. When the nights get colder, this dew gets transformed into frost.  

 
The combination of early morning dews, warm and wet weather and diminishing daylight hours increases the risk of fungal disease outbreaks. The right conditions to trigger these disease attacks are weakened or susceptible plants, a disease-producing organism (pathogen usually fungi) and weather conditions which favour the formation of fruiting bodies and spores (moist, mild wet conditions).

Most cool season turfgrass diseases spread via water droplets. Plants also release excess nutrients via their stomata's (gutation) during night hours when there is no sun and rarely any wind to evaporate it. These exudates become mixed with the dew water and become the perfect food source for disease pathogens in their early stages of development.

Many diseases that are occurring now have responded to the unusually warm, autumn weather conditions. Boundary layers around the leaves have stayed moist and humid. Relative humidity is important for spore germination and penetration of leaf tissues and constant wet conditions will allow the development and transportation of active fungi spores.

Most fungi grow well between 10°C - 40°C and function best at a pH range of 4-7pH. The current lack of cooler weather and sharp frosts has not helped in reducing these active pathogens.

The first step in turfgrass disease management is identifying the true nature of the problem. Diseases are only one cause of turf loss, and disease control measures will do nothing to alleviate damage from other causes such as management, wear or plant stress. It is therefore essential to determine whether the problem is disease, and if so, which disease.

Disease Triangle 

The three disease factors: susceptible grass / host, pathogen, and environment, provide the evidence for disease diagnosis. Symptoms are the expression of the susceptible grass to the disease and can take on a variety of forms.

Symptoms may appear on the leaves as small, circular, tan-coloured lesions surrounded by brown or purple borders (leaf spotting); as yellow, red, or tan blotches over most or all of the leaf blade (blighting); stunting; wilting; or as a brown or black rot on the crowns and roots. The appearance of these symptoms will also vary depending on the type of disease, the severity of the attack and the developing stage of the disease.

Fusarium disease 

Early identification of the symptoms is essential for good disease management; however the best form of management is using preventive, cultural turf maintenance methods that reduce the ideal environmental factors that these diseases require for development. E.g. regular brushing/switching of the grass to remove excess moisture, regular aeration to allow gaseous exchange and water percolation.

Turf grass diseases refer to a variety of fungal, bacterial, or viral infections that affect the health and appearance of grass in lawns, sports fields, golf courses, and other turf areas. These diseases can cause discoloration, thinning, wilting, and even death of the turf grass if left untreated. Different types of grasses are susceptible to specific diseases, and the severity of the disease can vary depending on environmental conditions and cultural practices.
Some common turf grass diseases include:

Brown Patch: This fungal disease primarily affects cool-season grasses during hot and humid conditions, causing circular patches of brown or tan grass.

Dollar Spot: Dollar Spot is another fungal disease that creates small, silver-dollar-sized spots on the turf, usually during warm and humid weather.
Pythium Blight: This disease is caused by a water mould and can quickly kill large areas of turf, especially in hot and wet conditions. It appears as irregularly shaped patches of discoloured, greasy-looking grass.

Leaf Spot: Leaf Spot is a fungal disease that causes small, circular spots on the grass blades. It is commonly seen in warm-season grasses during periods of high humidity or excessive moisture.

Rust: Rust is a fungal disease that gives the grass a rusty or orange appearance. It is often found in lawns with poor fertility or during cool and wet weather.

Snow Mould: Snow Mould is a fungal disease that develops under snow cover during winter. It appears as circular patches of matted, straw-colored grass when the snow melts.

Red Thread disease 

Red Thread: Red thread turf disease, also known as pink patch, is a common fungal infection that affects various types of grass, particularly fine fescues, ryegrasses.

Fusarium turf disease: also known as Fusarium patch or Fusarium blight, is a common fungal disease that affects turfgrass species. It is caused by various species of the Fusarium fungus, particularly Fusarium culmorum and Fusarium oxysporum.

Site characteristics and turf management practices have a large influence on disease management. Factors such as air movement, drainage, soil conditions, and the amount of sun or shade, slope, fertilisation and aeration programmes are important in influencing the development of turf diseases.
It is important to remember that pathogenic fungi can survive and remain in a dormant state in plant debris and soil until favourable conditions arrive again to stimulate another disease outbreak.

The Pathogens that cause these diseases are always around lying dormant in the thatch layers waiting for the ideal conditions to become active. Once these spores are activated and have found an appropriate host they are able to grow and reproduce themselves, spreading new spores and infections to other areas of turf. This cycle continues whilst favourable conditions prevail.

Understanding the disease cycle and implementing works that can break up the disease cycle will help reduce the opportunities for disease development and outbreak.

When it comes to disease identification, there is as much emphasis on you as the turf manager to provide appropriate turf samples for analysis as there is for the lab to accurately identify the problem. In most cases, the best place to remove a turf sample for analysis is from the leading edge of the symptoms, where the affected or discoloured plants give way to healthy turf.

However, we must recognise that by achieving good cultural practices to reduce thatch, improve air movement in soils, balanced feeding and correct mowing regimes will play an important part in promoting a vigorous healthy turf that can fight off and reduce the chance of disease attack.

We have also seen in recent years a trend towards more use of alternative products, such as organic fertilisers, compost teas, use of phosphite as well as tonics and bio stimulants to improve turf grass quality and help reduce disease incidence.

Good cultural practices may be the only option for disease control in the future especially as there are moves to reduce the amount of chemicals and fungicides available for use in the coming years. However, at the moment we are still able to reduce fungi pathogen populations by applying fungicides, which either kill off the pathogen or slow down the production of fungal spores.

Again, it is important to have identified the disease correctly, so that an appropriate fungicide can be selected. Using the wrong fungicide or wrong application rates can lead to a number of problems, not only would it be a waste of time and money, but the effect on the disease is also likely to be negative and may well exacerbate the problem by making the disease more resilient to the Active Ingredient applied.

Fungicides can be divided into two broad categories: contact fungicides and systemic fungicides. The contact fungicides generally are applied to the leaf and stem surfaces of grass plants. These materials may or can be washed or mowed off easily, which implies that they often only have a short term active durations, between 7-10 days. These fungicides are usually used to control foliar diseases and not diseases of the root and crown structures of the plant. Contact fungicides are used throughout the twelve months of the year.

Systemic fungicides have a different mode of action; the chemicals are absorbed and translocated within the plant’s tissues. Thus, they are not as likely to be removed from the plant by rainfall and mowing. Therefore, they are active for longer periods and can protect plants for up to 4 weeks. Most systemic fungicides can control both foliar and root / crown diseases. Use of systemic fungicides during colder months is not advised, as the plant is either dormant of slow growing and will not rapidly uptake the fungicide-greatly reducing its effectiveness.

Remember, prevention is key when it comes to disease outbreaks. By implementing these practices and maintaining good turf management practices, you can reduce the risk of diseases and keep your turf healthy and vibrant. If you encounter persistent or severe disease issues, consult with a local turfgrass professional or extension service for guidance tailored to your specific situation.

Please keep in mind that the use of fungicides should be done according to the instructions provided by the manufacturer and local regulations. It's also important to consider integrated pest management (IPM) practices, such as proper mowing, irrigation, and fertilisation, to maintain a healthy turf and reduce the need for fungicide applications.