Lawn Thatch: Pests and Disease

Lawns face a number of challenges for a variety of reasons, but the easiest way to manage the majority of these problems is to control the thatch buildup.

WHAT IS THATCH?

Thatch is an organic layer that accumulates between the soil surface and green vegetation of your lawn; a loose blend of stems and roots, both living and dead, that host and feed a variety of disease and pests (insects like Cinch Bugs, Sod Webworms and Lawn Grubs that will attract gophers, moles and voles!). Thatch becomes a problem when it gets than ½ an inch and roots grow into the thatch as if it was soil. Thatch dries very quickly in the heat and so those roots are more susceptible to drought.

Thatch builds up when your lawn produces the organic debris faster than it can be broken down. It is made up of the parts of your lawn that are most resistant to decay (stem nodes, crowns, fibers and roots). Although you'll find some leaf clippings in the thatch layer, they usually don't contribute to thatch build up because they’re broken down by the microorganisms in soil.

While you will never eliminate all the harmful bacteria and pests from your lawn, the proper care and watering of your lawn is important for controlling the thatch layer. Maintaining proper steady moisture keeps diseases at bay which can be very difficult if you have a thatch build-up and water can’t do its job. Many diseases thrive in thatch. Fungi is the primary cause of most disease and when a lawn is over-watered or under-watered due to an over-sized thatch layer, fungi appear.

Maintaining a healthy lawn does an enormous amount in itself to attract beneficial organisms and hold harmful ones in check. A healthy organic lawn encourages earthworms, microorganisms, butterflies, and the lacewings, ladybugs, and other insects that eat lawn and garden pests. A thick lawn doesn’t have many spaces in which weeds can establish themselves, and it’s generally able to beat back incursions from the fungi that exist in the soil.

Don’t give pests an opportunity. Make sure your lawn is properly watered and your grass is growing in good, healthy soil.

Selecting the right type of lawn for your climate creates the appropriate condition for its management and leads to healthy growth. For example, don’t install or try to care for a water-hungry variety in a water-starved area. Choosing a lawn that grows well in your climate will also make your lawn more pest resistant. The two types of lawn are grasses and fescues. Grass is difficult to care for and is more likely to develop a thatch layer; it isn’t as durable as fescue and often has to be periodically re-seeded.

Grasses are pretty but they have thinner, softer blades and are delicate. If you are experiencing thatch related issues, choosing a grass lawn may not be suitable for where you live. Fescue lawns seldom accumulate thatch if mowed properly. While fescue is coarser, it also has a thicker blade leaving less room for thatch to accumulate. Fescue tends to be resistant to disease and tolerant to drought. Jefferson Landscape and Design installs a dwarf fescue for our clients which is easy to manage. We highly recommend it for our area.

A good way to prevent potential thatch problems is to rake your lawn at least once a year using a metal-tined leaf rake and work the tines down to the surface. Finally, collect and remove all the debris. It’s highly unusual for a fescue lawn to accumulate more than ½ inch of thatch during the growing season. Fescue lawns don’t typically have thick thatch layers and if they do it’s typically due to improper mowing or excessive fertilizing. (Consider this: lawns grown in the right soil that have regular care and proper watering don’t typically require fertilizing.) Lawns like this will be weak and thin by the end of the summer.

Another way to handle a thatch problem, especially a bad one, is to de-thatch your lawn by renting a vertical mower or “de-thatcher” from a tool rental store. Vertical mowing is a way to cultivate the top later of soil and remove thatch. A de-thatcher should be used on a fescue lawn only if you re-seed immediately afterwards. Even then, be extremely careful. Vertical mowing is tricky and will damage the remaining fescue shoots. Make only one pass across your lawn and thoroughly rake and remove all the debris prior to re-seeding.

Thatch Shelters Grubs

Removing thatch makes your lawn far less hospitable to the unwelcome guest known as the lawn grub. Grubs can do a lot of damage to your lawn all on their own, especially in the fall, but they also attract moles and gophers! Lawn grubs are the larval stage of beetles. The larvae feed on grass roots until cool weather arrives. They spend the winter four to eight inches underground. In spring they surface, feed again, then burrow back into the earth where they pupate before emerging as adults after several weeks.

Birds are Grub predators. They consider these short, fat, white, worm-like things (beetle larvae which dine on grass roots) a delicacy. So, encourage birds to drop in and dine by putting out a bird-bath and change the water on a regular basis. Make the yard unattractive to moles by removing their food supply, make your lawn less attractive to grubs by removing the thatch layer.

Leaving a thatch layer in your lawn can potentially make your problems much worse, and it’s highly likely if you have lawn troubles at all it’s the thatch that brought it on (or your next-door neighbor’s).