With fall weather comes Brown Patch

Brown patch is a common disease of warm season turfgrass, particularly St. Augustine and zoysiagrass in Louisiana. The disease is caused by the fungus Rhizoctonia solani, and is favored by warm, wet overcast weather. It causes circular brown patches of infected grass in an otherwise healthy lawn. The patches start small, but overtime and under conducive environments the diseased patches will coalesce and leave your lawn looking dismal at best. Given less favorable weather for the fungus the turf can recover, and regrowth occurs in the center of the patch leaving a donut appearance in the recovering patch. To properly diagnose the disease, monitor for the indicative “patchy” symptoms and pull a blade of stolon (“running stem”) from the turf, and look for rotting of the crown. Leaf sheaths are easily pulled from the stolon because of the deterioration of the attachment point.

Brown patch development occurs most rapidly when temperature ranges from 70 and 85 degrees F and moisture is high. Fungal activity typically stops when temperatures exceed 90 degrees F or higher.

As with any disease or pest, the key to success is healthy plants. Fertilizer programs should follow the calendar recommendation as mentioned in the LSU AgCenter Louisiana Home Lawns: best management practice fact sheet as seen on www.lsuagcenter.com. Over fertilization, or fertilizing late or early, can lead to more susceptible tissues for the fungus to consume. For St. Augustine grass fertilizer programs should have halted in August.

In addition to improper fertilization, moisture plays an important role in the disease development. Proper drainage in your lawn is crucial to remove excess water from the turf. Watering in the late afternoon will cause the severity of the disease to increase. Lawns should be watered, when needed, in the morning so the sun can evaporate excess moisture from the turf. If your lawn is newly developed, proper establishment by deep waterings and proper fertilizer should have created a network of healthy roots, which should reduce the amount of watering needed in early fall-late spring.

To control this disease fungicides should be applied preventatively beginning about mid-September, with repeated applications as necessary throughout the fall being sure to follow the instructions on the label. As of 2010, homeowners have a new fungicide to add to their arsenal of turfgrass disease control products, Maxide Disease Killer, which contains the active ingredient azoxystrobin. This product is available at Lowe’s, Stine Lumber, Tractor Supply and elsewhere, and is formulated as a granular material containing 0.31% azoxystrobin. However, please be aware that Maxide has a similar product called Maxide Disease Killer Ready to Spray that contains the active ingredient propiconazole rather than azoxystrobin. Other chemicals that are somewhat effective include the active ingredients: maneb, myclobgutanil, PCNB, propiconazole, thiophanate methyl, and triadimefon. Products containing chlorothalonil are no longer labeled for use on residential lawns. Remember to always follow and read the directions on pesticide labels before use.

For more information contact aloyd@agcenter.lsu.edu