Symptoms and Cause of Dry Patch
Dry patch disease occurs during long hot, dry spells and tends to be more of a problem on free draining light sandy soils. The disease should not be so much of a problem on heavier soils.
The disease occurs when the soil becomes hydrophobic (water repellant) after a prolonged dry period where the soil has dried out completely. The soil particles become coated with a waxy substance which gives the dry patch its hydrophobic nature, and it isn’t easy to re-wet. Often it does not recover properly until the winter months when there has been substantial rainfall.
The first signs of the dry patch are irregularly shaped patches that show signs of drought stress. If you take a soil sample, you will notice that it is completely dry below the surface where these dry patches appear.
Treatment and control of Dry Patch
As with most problems that occur on lawns, preventative is better than cure. Try not to let the lawn dry out too much during periods of drought. If it does become a problem, the infected areas can be spiked to try and get the water down into the soil profile.
A wetting agent can be used to treat the hydrophobic area, which is the type of detergent. Wetting agents are widely used in the golf and sports turf industry to combat dry patch problems. Wetting agents help reduce surface runoff and help the water move through the root zone to where it is most needed.
Any aeration before applying a wetting agent would be very beneficial and increase the effectiveness of the wetting agent.
The dry patch would only be a severe problem during arid summers on lawns with light sandy soil. It should not be a problem during a normal wet British summer.