This past summer has been an exceptional year for diseases on turfgrass, and home lawns weren’t immune to these diseases either. Dr. Christian’s has mentioned several times this summer that this summer was the worst Brown Patch in Iowa he has seen in 30+ years. Summer temperatures often in the 80’s and lows in the upper 60’s with high humidity and rainfall made the conditions perfect for these summer diseases. The good news is that the temperatures seem to have cooled and repairs can be made to yards.
With the warm temperatures, ample rainfall, and high humidity this past summer, Iowa lawn’s endured prolonged periods of perfect weather conditions for brown patch (Rhizoctonia solani). This disease was noticed in Iowa from June on into September. It is often noticed as circular patches from a few inches to several feet.
Brown patch on creeping bentgrass putting greens at the Iowa State Horticulture Research Station.
The area in the patch can become killed and create a sunken patch, often though this disease will not completely kill the turf, but rather just thin those spots, which can recover with proper care after the weather conditions change. Brown patch lesions on leaves are easy to identify and are irregular tan or light brown in color with the edges of the lesions being a dark brown in color.
A close picture of brown patch lesions on turfgrass leaves.
Another problematic disease this summer was summer patch (Magnaporthe poae) which happens predominantly on Kentucky bluegrass and commonly occurs when temperatures are above 82. It is caused by a fungus that colonizes the roots. These patches often appear suddenly as small yellow patches, since the roots are affected, adding water will not help the declining turf health. As the grass dies it will turn a straw color. These patches often have areas inside of the patch that are not affected and seem healthy. Symptoms of summer patch will not be noticeable when the weather cools. Promoting healthy roots will help to minimize the impact of summer patch by regular aeration in the fall, mowing at proper mowing heights, and improving drainage in the yard.
If these diseases injured your turfgrass the fall is a great time to recover from them, as healthy turfgrass is the best way to combat weeds and disease next year. Make sure your yard is fertilized this fall, aeration each fall to improve gas exchanges to the roots and improve drainage making them healthier can help, follow proper mowing heights for the turfgrass species that are present in the yard, and overseed with more grass seed if large areas of dead turf exist.
Aerators can help improve drainage and promote healthy turf.
One final note, several calls and emails this week have been related to people mistaking disease damage for chemical damage. Remember that typically disease damage will be patchy, while chemical damage would be a complete grass kill or in straight lines.
Below are a couple pictures of disease damage on lawns from the Ames area:
For more information on how to renovate a yard visit: https://www.extension.iastate.edu/turfgrass/search/content?f=im_field_...