Dew dispersal – all you need to know

Dew is a common problem at this time of year but dealing with it can be time consuming. Peter Corbett from Origin Amenity Solutions details the chemical products that are available to help golf clubs manage this more efficiently – and the robots that might be deployed to do this in the future.

What is dew?

Dew is formed when the surface temperature of turf and air falls. When the foliage becomes cool enough, the air around the object will also cool. Colder air is less able to hold water vapour than warm air. This forces water vapour in the air around cooling objects to condense and to form droplets on the turf, hence the formation of dew.

Dew must not be confused with guttation, which is produced directly by the turf which exudes vascular sap from the xylem. During the night grass does not transpire so the stomata are closed, during periods of high soil moisture water enters the roots creating root pressure, which forces water up the plant and out via specialist pores known as hydathodes. This creates droplets on leaves which can be confused with dew.

Why reduce?

Remember the classic disease triangle or pyramid? The concept of the host-pathogen-environment interaction has been known in plant pathology since the 1840s. Disease modelling is not a new concept; it was discovered nearly 200 years ago and we are still working out the complexity to produce accurate prediction models.

Background

Dew and guttation removal has been shown to reduce disease levels for many foliar diseases such as microdochium and dollar spot in a wide range of trials and in commercial practice. Removal of these droplets is now included as a critical element of any integrated pest management (IPM) systems and with the loss of truly curative synthetic fungicides, it is an important component in any good practice fungicide programme.

How to remove or reduce dew and guttation

Water is a unique liquid; its properties are a result of its chemical structure and surface tension. It is this surface tension that creates droplets, that is dew, guttation, frost.

1. Physical removal by disturbance – water or guttation drops can be disturbed breaking down the surface tension to remove them from the leaf surface.

This is very effective but time consuming, and dew or guttation can reform very quickly if suitable conditions prevail . Your options are:

• Manual or mechanical switching using brush, roller, rope;

• Use of GPS autonomous robots has been trialled by Origin Amenity Solutions (OAS) at our research centre since the autumn. This technique is very cost effective and can be timed to occur at optimum timing for removal.

2. Chemical prevention – reduction of surface tension.

To break down the surface tension of water we can either add surfactants to water or transform the leaf surface with surfactants to break down surface tension. This causes droplets to collapse, consolidate and fall to the soil leaving the leaf dry. This creates an environment less favourable to development of foliar diseases.

Chemical surfactants

There are a wide range of molecules that have the ability to break down water surface tension. In order to be an effective dew or guttation dispersal agent, the molecules require certain characteristics:

• When carried in water, that is as a spray, they have the ability to stick to leaf surface and dry. Once on the surface of the grass they have the physicochemical ability to break down surface tension. Ideally the molecules need to be photostable and persist in an active form for two to four weeks.

On the left, treated with Dewcure, on the right, untreated

• To get best results all dew dispersal products need to be applied:

– Evenly using a suitable droplet spectrum for the target leaf;

– To a dry leaf which has not been treated by any other surfactant product for at least five days.

Dew should not be confused with guttation

There are many dew dispersants (surfactants) available on the market. Origin Amenity Solutions has two specific products for this use containing different active ingredients, Dewcure and Dew T. In addition, the company has a penetrant product which also provides dew suppression in most situations, called Penetr8-R.

For more information or advice on dew management products, contact Origin Amenity Solutions on 0800 138 7222 or email sales@originamenity.com