With cool, wet weather, expect to find brown patch in lawns.

Brown patch is caused by the fungus Rhizoctonia solani. The disease is characterized by the development of somewhat circular patches of diseased turf that can become quite large if not treated.

The brown patch fungus does not usually kill the grass, but it will attack the base of the leaf sheaths, causing them to rot. This results in thinned areas of turf that will allow the invasion of weeds. Brown patch generally develops first in areas surrounded by trees, shrubs and fences that reduce air movement or in low lying areas that delay the drying of the grass following rain or irrigation.

It develops most rapidly when nighttime temperatures range from 60-75°F and daytime temperatures do not exceed 85-90°F.

If areas of your lawn were affected by brown patch in the fall, you can expect to see it again this spring. Applications of fungicides can limit damage to the turf until conditions become unfavorable for disease development.

When fungicides are being applied to prevent disease in areas where it has not already become established, the use of granular formulations of fungicides is appropriate. Once the fungicide has been applied, it must be watered to activate it.

However, if fungicides are being applied to areas where brown patch is already active, it is better to use sprayable formulations of the fungicides, as these will give better coverage. In this case, the material should be allowed to dry before additional water is applied.

Two applications about a month apart are preferable as long as the grass is actively growing.

Fungicides available for homeowner use include those with the active ingredients myclobutanil (Spectracide Immunox Lawn Disease Control, Ferti-lome F-Stop, Green Light Fung-Away, etc.), propiconazole (Bonide Fung-onil Lawn & Garden Disease Control, Ferti-lome Liquid Systemic Fungicide, etc.) and thiophanate-methyl (Ferti-lome Halt Systemic Rose, Flower, Lawn, Ornamental Fungicide, Bonide Infuse Systemic Disease Control Lawn & Landscape Granules, etc.) all of which do a good job of controlling brown patch.

Follow label directions for proper use.

Craig Roussel, is a Horticulture Agent for LSU AgCenter covering Ascension and St. James Parishes. He can be reached at 225-562-2320 or 225-621-5799.