Berks County Cooperative Extension -

TURFGRASS - FAQ

What is aeration?

Aeration is a remedy for compacted soil. A layer of soil as thin as .25 or .50 inches can severely retard water infiltration. Compaction also interferes with the necessary escape of carbon dioxide from the soil and the capture of oxygen by the soil. Compacted soils are associated with acceleration of thatch accumulation.

Aeration is accomplished with an aerator (aerifier), a machine with hollow tines that removes plugs of soil from the lawn. For best results, run the aerator over the lawn, then make a second run perpendicular to the path of the initial run. Slightly moist soil is desirable since the tines will penetrate farther than under dry conditions, which may cause the tines to ride on or only slightly pierce the surface.

Spring and fall - times of vigorous growth for most turfgrasses - are the recommended times to undertake aeration. Aeration of lawns containing predominantly cool-season grasses, such as Kentucky bluegrass, should not be done during the summer when these grasses are in a semi-dormant state.

Hollow-tined aerators should not be confused with solid-tine spikers, which do not remove plugs from the soil. Solid-tine spikers actually increase soil compaction.

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How can crabgrass be controlled?

Crabgrass is a summer annual grass or, put another way, a weed. Crabgrass is perpetuated by seeds, which are set from mid-summer to frost. Seed production is abundant and can occur at mowing heights as low as .25 inches. Seeds germinate from mid-spring to mid-summer. After it is established, crabgrass withstands drought, high temperatures and compacted soils better than most turfgrasses.

Controlling crabgrass in a lawn with an established population, where the soil contains a significant number of seeds, should be viewed as an ongoing project. The goal of the project is to stop reinfestation by preventing reseeding. If seed production is controlled for several years, the number of seeds remaining in the soil will be reduced to the point where crabgrass can be managed through manual removal of indivdual plants.

Reduction of the number of seeds in the soil to a manageable level is best accomplished by application of a pre-emergent herbicide. This type of herbicide establishes a chemical barrier in the soil that prevents crabgrass seedlings from emerging and developing. As is the case with all chemicals, one should carefully read the label and follow application instructions. Of special concern with this type of herbicide is the long lasting residual effect in the soil which may adversely affect newly seeded turfgrass. If seeding of turfgrass is planned following application, pay particular attention to the recommended interval on the label between application and seeding new turfgrass. For maximum effectiveness, the herbicide should be watered-in within two or three days of application. Consult the label for additional information.

Timing is everything when it comes to application of a preemergent herbicide. While it is commonly assumed that blooming of forsythia signals the time to apply the herbicide, this assumption does not always ring true. Under normal conditions, in this part of Pennsylvania preemergent herbicides for control of crabgrass should be applied between March 15 and April 15.

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What is snow mold?

Snow mold is a fungal disease that attacks turfgrass. While several types of snow mold exist, the most common form in this area is gray snow mold (Typhula Incarnata). Signs of this disease are usually noticed in the spring as the snow melts and typically appear as off-color, crusted, matted leaves of turfgrass. Affected areas may range from several inches to several feet across. Fungal bodies, called sclerotia, are responsible for creating patches of snow mold. If there is no snow cover or if snow rests atop frozen soil, gray snow mold is unlikely to occur.

While a application of a fungicide may be warranted in unusual cases, gray snow mold can for the most part be successfully controlled with the proper cultural practices. Starting in the fall, refrain from applying high nitrogen fertilizers, keep the grass well-mowed into the late fall (uncut grass bends under the weight of snow and mats easily) and thoroughly rake the lawn to remove any clippings that have not decomposed. In the winter, try to avoid making paths in the snow inasmuch as packed snow tends to melt gradually. If making a path is unavoidable, disturb the packed snow to hasten melting. In spring, if symptoms are present, rake the infected area to break the encrusted area to encourage new growth. In the vast majority of cases, gray snow mold affects only the blades of turfgrass and does not kill crowns and roots.

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Sources: The Penn State Master Gardener Manual, Landschoot, Managing Turfgrass Diseases (Penn State University), Burpeenews, Listserv (11/15/99)
Document created: 15 December 1999; Revised: 3 March 2001