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Many Lawn Diseases Can Be Controlled with Fall Treatments
by Don Janssen, UNL Extension Educator
Many of the lawn diseases that have plagued homeowners this summer can be controlled effectively through sound management practices and timely application of fungicides this fall.
If leaf spot, melting-out, dollar spot or summer patch were present in your lawn this summer, take preventive measures now to prevent further turf injury and recurrence of disease problems next year.
Cooler fall weather may slow or mask the symptoms of some diseases such as summer patch, but heavier dews will promote leaf spot development. These two diseases will be back next season, perhaps in more severe form, unless corrective steps are taken this fall.
Bipolaris (Helminthosporium) leaf spot and melting-out develop during cooler, wet weather in fall and early spring. The fungi causing these diseases survive the winter in the thatch layer and in infected crowns and roots. One or two fall fungicide applications are recommended to reduce the amount of leaf spot and minimize pathogen carryover through the winter. These fall applications will increase the effectiveness of the fungicide program in the spring.
The best preventive measure is to use leaf spot-resistant cultivars when establishing a new lawn or renovation an old one. A blend of three or more improved Kentucky bluegrass cultivars resistant to leaf spot provides optimum protection against this disease and reduces the possibility of costly fungicide spray programs.
Snow molds attack lawns from late fall to mid-spring. Snow mold injury can be avoided or greatly reduced by good management practices. Again, adequate fertilization is important, but do not use high nitrogen content fertilizers after September. For best results, fall fertilizer applications should be timed to coincide with final mowing in the fall. Maintain the lawn at a height of 1 1/2 to 2 inches until growth stops. If snow molds are a recurring problem, the use of preventive fungicide is advised. Time the initial application approximately one month before the lasting snow. A second application may be necessary if a midwinter thaw occurs, followed by a third application in early spring if cool, wet weather persists.
The use of fungicides on lawns can be minimized if homeowners will make a serious effort to follow recommended maintenance practices. Many serious lawn diseases can be avoided or the damage reduced by the use of resistant cultivars, proper and timely fertilizer applications, adequate watering, mowing at the recommended height and frequency and preventing thatch from accumulating. If fungicides are necessary to control severe attacks, their effectiveness is directly related to how well the lawn is maintained.
Following are some fall disease management practices:
-- Use a blend of disease-resistant Kentucky bluegrass cultivars for overseeding to help reduce the need for chemical applications for disease control and to maintain a good grass stand. Overseeding will need to be done over a period of several years to be effective. Blend at least three cultivars of Kentucky bluegrass.
-- Aerify the soil by coring.
-- Reduce the cutting height on bluegrass lawns; do not remove more than 30 percent of the grass at each mowing.
--Maintain deep watering to avoid desiccation problems if we have an open winter.
--Time fall fertilizer applications to coincide with the final mowing. Avoid fast-release nitrogen carrier fertilizers.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
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