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Larry Sagers Horticultural Specialist Utah State University Extension Service Thanksgiving Point Office © All Rights Reserved
For more on turfgrass diseases, read my column in yesterday’s Deseret Morning News.
If you are seeing spots before your eyes, perhaps it is time you visit your eye doctor. Then again if the spots are on your lawn, they are coming from one of several fungal diseases that might be attacking your lawn this season.
Of course we can blame it on the rain and temperature. We previously covered a number of different problems afflicting our trees because of the spring rains. The abundant moisture shifted the ecosystem to react like our lawns are in the Northeast or Northwest states and we are now dealing with the same problems they have had in lawns for years.
The major turfgrass diseases are caused by fungi. These pathogens attack both the roots and the leaves of the plants. The symptoms then appear, and these are usually spots of dead grass before your eyes.
Of all of the pest problems, I have dealt with over the years, turfgrass diseases are usually the worst. They often produce symptoms that are hard to recognize and the pathogens themselves can only be identified in a laboratory.
I cannot stress strongly enough that you get the problem identified correctly before undertaking a control program. Even after the diseases are identified, control measures are not always effective and it may take considerable time before your grass recovers.
No fungicide works on all diseases. If you use the wrong product you waste time and money. In some cases using the wrong fungicide makes the disease worse. The following turfgrass diseases are those most likely to show up in your lawn right now.
Melting out describes the symptom of this disease. Your grass starts to grow well in the spring, and then when warm weather comes, it fades or melts away. It appears to need water and yet more water does not help and it often makes the problem much worse.
This disease attacks bluegrass and perennial ryegrass. The fungus survives in plant debris or infected plants. Leaf infections are most common in cooler months and the disease spreads by wind, splashing rain, grass clippings, or by equipment. The problem is aggravated on lawns that are cut too short.
Necrotic ringspot is another aggravating disease that attacks bluegrass and fine fescue. It has become a problem particularly on 2- to 5-year-old Kentucky bluegrass turf established from sod. Turf established from seed also has shown the disease but much less frequently. The fungus infects roots and rhizomes, covering them with dark strands of fungal growth. It overwinters in infected plant material.
The obvious symptoms are dead circles and arcs ranging from several inches to several feet in diameter. These start to show up as soon as the grass gets under stress. Weeds or resistant grass species often grow back in the dead turf area.
Fairy rings are circles of darker-green, faster- growing turf grass often with a ring of thin or dead grass inside or outside. They range from two to several hundred feet in diameter. The fungi may prevent water from penetrating the soil creating the dead ring.
Fairy ring is caused by many soil-inhabiting mushroom fungi that grow very extensively near the ring. Growth usually starts with a germinating spore at a central point, and the fungi grows outward at the rate of a few inches to two feet or more per year.
Mushrooms (toadstools) and puffballs often grow throughout the lawn without being associated with fairy rings. They are mostly annoying although some are foul- smelling and a few are poisonous and a menace to children and pets.
The following cultural control measures apply to most fungal diseases that attack lawns in Utah.
Avoid excess soluble nitrogen through fall and winter and spring. Use slow release fertilizers including sulfur-coated urea.
Raise your mower height to mow bluegrass 3-3.5 inches high and mow frequently enough to not remove more than one third of the grass blade at each mowing.
Aerate your lawn to control excess thatch, to reduce soil compaction and to allow the water to penetrate.
Water your lawns deeply and infrequently. Light, shallow irrigation on a daily basis makes your lawn highly susceptible to fungal infections. Dry warm conditions control most lawn fungi.
Some types of grass and some varieties of grass are more resistant to diseases than others. If problems persist, overseed with resistant varieties.
With time the spots should disappear and your lawn will look good again. Now if only the warm weather would not bring out the insects, we would not have to see these spots in our lawns.
If you are struggling with a spotted lawn, try pulling up on the grass. Most insects chew off the roots so the lawn lifts easily because there are no roots. If you need help identifying the disease, take them into the Utah State University Extension Service Office in your county.
If they are unable to identify the problem, they may need to send them to the USU diagnostic laboratory in Logan. Take in a sample of sod at least 12 inches square and include the healthy turf on one side and the dead grass on the other. Samples of just dead grass are not useful for diagnosing the problems.
For recommendations of pesticides to control lawn diseases in Utah and pictures of those diseases, click onto this website. http://extension.usu.edu/plantpath/turf/turf\_disease\_utah.htm
