Monday, May 18, 2009

Defending Your Turf from Pests & Problems

Part three in a three-part series on environmental lawn care

A well-established, properly maintained lawn is naturally weed and pest resistant -- for the most part. For the other part, we need to consider a few more issues than just mowing, watering, and fertilizing correctly.

One of the great axioms of gardening is to “use the right plant in the right place.” For lawns, this means selecting a turfgrass variety suitable for your growing conditions and the amount of traffic the area will receive. Trying to establish a healthy lawn using the wrong kind of grass is as frustrating (and pointless) as baking a nonfat cheesecake.

For sunny lawns, tall fescue is the most recommended type of cool season grass, combining heat and drought tolerance with resistance to the most common diseases and pests while also holding its own in areas used for recreation.

In shadier areas, fine fescues perform best, although the thinner, more delicate blades are more sensitive to traffic, and also require well-drained soils. Red fescue is a variety gaining in popularity as it becomes established quickly and requires surprisingly little maintenance. In fact, depending on its use and location, it can provide a lush appearance even without mowing.

The most popular warm season grass is zoysia, renowned for its drought and disease tolerance and low maintenance needs. It is also somewhat infamous for invading neighboring fescue lawns and browning out from October until May. Zoysia needs full sun, loathes shade of any kind, and can take years to become fully established.

Naturally, there are other popular varieties, like Kentucky bluegrass and perennial ryegrass, as well as numerous cultivars and varietal blends. For the best and latest advice on the newest cultivars and guidance on selecting good seed sources, contact your local Cooperative Extension Service office, usually county-based, although you may need to contact the state office. Check the blue government pages of your phone directory, or search online (search cooperative extension service [and add your state or county name]).

One of the goals of cutting grass at the highest possible setting is to shade out many of the noisome broadleaf weeds which need plenty of light to grow, and whose seeds need light to germinate. In addition, providing just the right amount of nutrients and watering properly to ensure deep, dense root development will also help develop a thick mass of turf which can easily shoulder-out most weeds.

Of course, if you are just embarking on this new approach to lawn care, you might still have some weeds needing attention. For some people, simply providing the proper care for a lawn will lead to the decline of most weeds, although it may take a number of years, which is just fine with them. They tolerate a few wild violets, dandelions, and patch or two of clover. It is only a lawn after all.

For the more fastidious, whose lawns are valued gardens of grass, there are several non-toxic approaches worth consideration. One of the most exciting is corn power. Agronomists in Iowa, always looking for new ways to use corn, have discovered that corn gluten is an extremely effective pre-emergent weed control for crabgrass, dandelions, clover, purslane, among others, when applied in early spring. It will not kill existing perennial weeds, but it will prevent seeds from germinating, and also provides a low-dose of organic nitrogen to feed your lawn at the same time.

Some perennial weeds, such as wild strawberry and ground ivy, will thrive only when soils are particularly acidic. Liming will balance the pH of your soil, improving nutrient uptake by grass plants and spelling doom for the weeds. Be sure to conduct a soil test before liming. Soil test kits are usually available for a nominal fee ($5-10) from your local county cooperative extension service; many garden centers and nurseries also provide soil testing, though usually at a substantially higher price ($25-50). (Learn more about soil testing by viewing Putting Your Soil to the Test, April 10, 2009.)

One of the most common problems experienced in our region is compacted soil. Our naturally clay-heavy soils compact readily, which inhibits grass growth, water penetration and drainage, and leads to bald patches and weed growth. Moss is a good indicator of compacted soils in shady areas and plantain of compaction in sunny locations.

You can prevent some compaction by limiting foot traffic across your lawn, never walking on wet grass, and by changing your mowing pattern. Instead of always mowing from north to south every week, alternate with an east-west pattern, or mix in a diagonal or circular pattern.
Aeration is one of the least appreciated measures to ensure a lush, healthy lawn. In many respects, aerating is far more important than fertilizing and liming, and easily worth the investment every several years.

Core aeration is the most effective approach, and you can rent a motorized machine to extract plugs from the soil, although aeration is often best left to professional lawn care services, which can be more cost-effective in the short run. Professionals typically charge 40 to 80 dollars for the average 5,000-10,000 square foot lawn.

Smaller lawn areas can be manually aerated using a spading fork inserted into the soil at a 45 degree angle. Insert tines to approximately four inches and push down, rocking back and forth a bit, and loosening the soil. Repeat this process every 12-16 inches until the entire lawn area is covered.

Aeration also helps to break up thatch, which become problematic when it exceeds a half-inch in depth. Power raking will also eliminate thatch, but requires significant raking and clean-up, while core aeration does it all with a minimum of fuss.

Like many of the weeds we have seen, insect pests are frequently indicators of poor turf conditions, such as a lawn under stress from overwatering, improper watering, and overfeeding.

However, some pests, including sod webworm, chinch bugs, and grubs, may require some additional action. Fortunately, non-toxic organic controls are available, often derived from flowers, fruits, and nuts, in addition to bacterial controls, including Bacillus thuringiensis, (B.t.) a native bacteria commonly found in soil and on plants, and Milky Spore, probably the first and most famous bacterial control agent.

Lastly, some lawns will fall prey to a variety of diseases, from summer patch and fairy rings to rust, powdery mildew, sooty mold, and red thread. These fungal outbreaks and diseases are best controlled by careful attention to nutrient application, soil aeration, and proper watering. In the worst cases, reseeding may be necessary, particularly using a more resistant variety of grass.

Copyright 2009, Joseph M. Keyser

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