Summertime Lawn Care and Problems

Robert J. Souvestre  |  7/18/2011 10:07:59 PM

Take-all Root Rot is a summer disease that can be quite destructive. Affected areas allow weeds to invade the lawn.

Lawns and the people who maintain them face a number of issues in mid- to late summer. A variety of lawn-care activities and pest problems need to be dealt with this time of the year.

Whether you are repairing damaged areas of your lawn where grass has been lost or establishing a whole new lawn, this is a good time to lay sod. When laying a new lawn, kill off existing vegetation with glyphosate herbicide. Remove the dead vegetation because sod should be laid on bare soil. It’s best to lightly till or rake the area to break up the top crust before laying the sod. And work out a rough grade to move surface water away from buildings, especially the house.

If you are laying the sod yourself, select fresh-cut Louisiana-grown sod (or grown as close to Louisiana as you can find). Lay sod pieces tightly touching each other in a solid coverage pattern resembling that of a brick wall. A lawn roller (available at local rental companies) will level the lawn if it appears lumpy.

After installing the sod, water it for about 20 minutes daily for the first week to 10 days if it doesn’t rain. During the second week to 10 days, water about 30 or 40 minutes every three days as needed.

Wait until the grass looks like it needs to be mowed before mowing. Mow with a mower setting of 2 inches for centipede grass and 3 inches for St. Augustine. Healthy sod should not need immediate fertilization. About four to six weeks after installation may be a good time to apply a half-rate of fertilize.

Several lawn diseases are active in summer. Most are encouraged to attack when weather is hot and wet. A common lawn disease called brown patch (or large patch) is more active in spring and fall, but can sometimes occur during summer.

Take-all root rot, caused by the soilborne fungus Gaeumannomyces graminis var. graminis (Ggg), is a summer disease of all warm-season turfgrasses we grow. As the name implies, this is a root disease that can be quite destructive. The following information is provided by Don Ferrin, an LSU AgCenter specialist in the Department of Plant Pathology and Crop Physiology.

Initial symptoms of take-all root rot are a general yellowing, thinning or drought-stressed appearance of the turf. The overall density of the root system is greatly reduced. As the disease progresses, irregular patches of dead grass develop, and diseased roots appear dark-colored and tend to be short and brittle. Careful examination of stems that grow along the surface of the ground and the bases of the leaf sheaths with a good hand lens will usually reveal the black, fungal fibers Ggg on their surfaces.

The management of take-all root rot relies primarily on the use of good management practices to reduce stress on the turf and alter the soil environment to make it more suitable for root growth and less suitable for the pathogen. The first step is to alleviate the stresses that triggered the disease. These stresses can include soil compaction, improper watering, improper soil pH, improper mowing height and the overuse of herbicides.

None of the fungicides that are readily available to homeowners are particularly effective in controlling this disease by themselves once the disease has become established. However, commercial products like the strobilurins (azoxystrobin and pyraclostrobin) and to a lesser degree the triazoles (triadimefon and propiconazole) may aid in control when they are used as part of an integrated management program. Current recommendations are to make two applications in the fall (mid- to late September and again in mid- to late October) and one application in the spring (mid- to late March). Each application should be watered in with at least 1/4 inch of water to move the fungicide into the root zone where it is needed to protect the roots.

Many of the herbicides we use during the cooler spring or early summer period are more likely to discolor lawn grasses if they are used when weather is hot. However, Dan Gill, LSU AgCenter Consumer Horticulturist, offers these options.

You can use any of the selective lawn weed killers now if you spot treat (make sure the label states it is safe to use on the type of grass you have and will control the particular weeds that are in your lawn). That means applying the herbicide spray just to patches of weeds rather than the entire lawn. It may take more than one treatment for effective control. So if needed, make sure you do followup applications following label directions.

If weeds are generally scattered throughout the lawn, applying the herbicide over the entire lawn will give best results. Two that can be applied despite the heat are imazaquin (Image – controls a variety of broadleaf weeds and sedges like nutgrass) and penoxsulam (Green Light Wipe Out for Tough Weeds in Lawns or Ferti-loam Dollarweed Control Plus – labeled to control a variety of broadleaf weeds).

Providing the proper care for your lawn will keep it looking its best and go a long way in preventing problems with diseases and weeds. “Louisiana Lawns Best Management Practices” is a for-sale publication ($5) produced by the LSU AgCenter. It has detailed information on proper fertilization, watering and mowing. And it includes an excellent pest management section with photos of common weeds, insects and diseases to help you diagnose problems. You can purchase it online at the LSU AgCenter Online Store.
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