How to Prevent the Top 10 Lawn Pests and Diseases
Lawns can become vulnerable to pests and diseases for many reasons, including restricted air movement, poor drainage, a lack or excess of nutrients, and incorrect soil pH. There are also some grass species that are more susceptible, and some weather conditions that are simply more favorable for attack.
Prevention is better than cure, and with limited chemical treatments available to the amateur it is best to try to reduce the risk of pest and disease attacks wherever possible. Regular mowing keeps the grass healthy and strong, while removing the clippings helps to prevent a build-up of fungal spores. Avoid high nitrogen feeds during the fall — this encourages long, lush growth that is more susceptible to snow mold, rust, and other fungal diseases.
1. Slime Mold
Commonly found in late summer and fall, slime molds don't actually cause harm to the grass, although they are unsightly and unpleasant if sat on. There isn't a cure for the problem, although regular aeration and scarifying reduce the risk of most fungi on the lawn. They can be removed immediately by spraying with a jet of water.
2. Red Thread
Probably the most common lawn disease, red thread causes patches of red-tinged grass, which turn brown and die back. It is often associated with nitrogen deficiency, so feed the lawn with ammonium sulfate as soon as symptoms are spotted; it is usually worst after wet summers and falls. Regularly aerate and scarify to improve air circulation.
This disease can spread rapidly through a lawn, creating yellow patches. Up close, rusty orange pustules can be seen on the grass blades. No chemical control is available, but regular mowing and the removal of clippings will prevent it from spreading. Avoid using high nitrogen fertilizers in the fall. This can cause lank growth, which is more susceptible to disease.
4. Snow Mold (Fusarium patch)
Most commonly seen in the fall or after snow, this fungal disease appears as yellow or brownish patches on the lawn, occasionally with a layer of white or sometimes pink mold that looks similar to cobwebs. Patches can spread rapidly and destroy a lawn. Scarification can help reduce the risk, as can avoiding high nitrogen feeds in the fall.
5. Ant Nests
Ant hills look ugly on a lawn, and if they cannot be tolerated, consider using the nematode Steinernema feltiae as a biological control, which is available from mail order companies. The commercial ant powders and sprays available for controlling ants are usually for use in buildings and not effective outdoors where ant nests can be deep in the soil.
6. Chafer Grubs
These unattractive grubs are the larvae of the chafer beetle and cause problems not only because they feed on grass roots but also because creatures such as badgers and birds often tear the lawn up in order to eat them. Biological control involves watering in nematodes, which are available by mail order, although chemical controls are also available.
7. Fairy Rings
These often appear as irregular dead circles in the lawn or as a ring of toadstools. Effective chemical controls are only available to professionals, so the only possible solution, which is not always feasible, is to dig out the affected area to a depth of 12 inches (30 cm) and replace it with healthy topsoil before seeding or turfing the surface.
These are the larval stage of crane flies, or daddy longlegs, and cause yellow or brown patches on the lawn surface as they eat through the roots below. To make it worse, birds may tear up the lawn as they attempt to dig down and feed on the larvae. To control, cover the lawn with plastic to draw the larvae to the surface, and then allow the birds to feed on them.
The underground tunneling of moles as they search for worms and grubs leads to the creation of mole hills when the soil is deposited on the surface of the lawn. This makes mowing difficult, creates bare soil for weeds to germinate in, and destabilizes the lawn. Placing mole traps in the tunnels is the only effective method of control.
10. Worm Casts
The casts left by worms on the lawn surface are an unsightly mess. They should be brushed off when dry or otherwise they will be smeared during mowing, and this kills the grass underneath them, leaving bare soil for weeds to germinate in. Don't overwater a lawn since worms love moist conditions. Use a switch regularly to remove excess moisture.