Brown Patch Fungus hits lawns
Amy Jordan
Thursday, July 12, 2007
Recent weather has been ideal for the development of disease on plants.
Lawns have been especially vulnerable to damage, with a fungus called Brown Patch affecting tall fescue across the state.
According to Megan Kennelly, plant pathologist with K-State Research and Extension, the fungus becomes highly active when conditions are moist and night temperatures are above 65 degrees.
Brown patch symptoms develop in 24 to 48 hours during warm, humid weather. Patches initially are dark purple-green, but then quickly fade to light tan or brown as the diseased leaves dry out. Diseased turf may appear drought stressed even when the soil is moist. The pattern of damage is variable.
Damaged areas sometimes form circular patches of blighted turf from several inches to several feet in diameter. However, damage often develops in a more irregular pattern without formation of circular patches.
The pathogen mostly infects the foliage and makes lesions with a brown border, and the leaves in affected areas are killed. Changes in the weather or applications of fungicides will slow down the pathogen, new leaves will emerge, and the turf will recover in 2 to 4 weeks. In extreme cases the pathogen can infect crowns or stems, leaving weak areas of turf that are susceptible to invasion by weeds. Overseeding in the fall may be necessary in areas of thin turf.
The brown patch pathogen survives for a long time, and most lawns have plenty of fungus already present. Since we can’t eliminate the fungus the key is to manage the turf so that conditions are not favorable for disease. Irrigation is the most important factor to manage. This disease is favored by long periods of leaf wetness. Do not irrigate in the evening—this leads to a long, wet period overnight that extends into the dew period in the morning. Water in the morning instead. Fertility is the second most important factor. Don’t over fertilize, and don’t fertilize if you have active brown patch. Research at K-State has demonstrated that returning grass clippings to the lawn has no effect on brown patch so don’t worry about spreading the disease in clippings.
Chemical controls are available to suppress further injury. Several products available for homeowners are Captan, Myclobutanil, Thiophanate-methyl, and Triadimefon. Repeat applications may be necessary. Commercial lawn care professionals have access to other products that are more effective, and if you demand a very high quality you might wish to contact a lawn company.
In many cases, however, the turf recovers on its own after a couple of weeks, especially after a change in the weather. So, consider whether you really want to treat or whether you can wait for the disease to run its course and go away naturally.
F Amy Jordan is a horticulturist with K-State Research and Extension in Lyon County.