Towards the end of summer and into autumn you will start noticing more frequent and heavier dew forming on your turf surfaces.  A heavy dew will reduce the quality of cut and can increase susceptibility of autumn disease outbreaks.  Switching, rolling and use of surfactant dew dispersants can all be used to reduce the effects of dew on your turf.

Condensation is the process by which water vapor in the air is converted into liquid water.  The droplets of water that form on exposed objects as a result of this process is known as dew.

Condensation occurs and dew droplets form when temperatures drop and exposed objects start to cool down, usually at night.  If an object becomes cold enough, the air surrounding it will also start too cool.  Cold air cannot hold as much water vapor as warm air and consequently, water vapor in the air around the cooling objects condenses, forming tiny droplets of water – dew.

The temperature at which dew forms is called the dew point.  The dew point varies widely depending on location, weather, time of day and season.  For example, warm, humid areas are more likely to experience dew than cooler, drier places. The greatest number of ‘dew’ days occur in autumn, and early spring but dew will form whenever the ‘dew point’ is reached.

Should I be concerned about the presence of dew on my turf?

The formation of dew on grass leaves can be problematic for turf managers because it can create the ideal conditions for the formation and spread of fungal diseases such as red thread (Laetisaria fuciformis) and michrodochium patch (Michrodochium nivale).  All pathogenic fungi benefit from ‘free’ moisture on turf leaves, allowing fungal spores to spread across the surface and increasing the opportunity for infection to occur.

A wet turf surface also negatively effects the quality of cut that can be achieved when mowing, therefore impacting on presentation and potentially providing more opportunity for diseases to invade where the cleanness of cut is poor, resulting in a greater level of damage to the grass blades.

Should I remove dew from my turf?

Ideally dew should be removed from turf at the earliest opportunity to minimise the chance for disease spread and infection and to improve the quality/cleanness of cut before mowing.  As dew usually occurs overnight, dew removal should be prioritised as the first job of the day whenever dew formation has occurred.

How do I remove dew from my turf?

There are multiple techniques that you could use to remove dew: 

• The most basic and straight forward approach would be to use a brush or switch to physically remove dew droplets from the grass blade surface, therefore speeding up the leaf drying process. A tractor mounted brush or rubber drag mat, could be used for larger areas of turf.
• Apply a surfactant (wetting agent) designed to prevent dew formation for a given period of time (usually around 3-4 weeks). These products are particularly useful where it is not possible to physically remove dew on a daily basis or for reducing the manpower required to maintain a particular area, allowing turf managers and their staff to get on with other jobs.  This is also a good option for larger areas of turf, depending on the maintenance budget available.
• Mowing an area will also remove dew from the surface, however, as discussed above, this is not always the best option as it will reduce the cleanness of cut and may increase the chance for disease infections to occur.

Is there anything else I can do to minimise the presence of dew?

Improving airflow around turf areas and reducing shade are also important to reducing dew formation/turf leaf wetness.  Minimising obstacles around the edge of a turf area will increase airflow and can reduce the likelihood of dew forming.  Increasing airflow will also aid the leaf drying process subsequent to dew removal.

Similarly, shade increases the length of time grass blades remain wet.  Maximising morning sunlight, particularly to southern and eastern horizons, is particularly important to encourage surface drying as well as for maintaining generally good turf health.  Remember, a healthy turf plant will always be more resistant to disease infection than a weak one!