For the most part the lawns enjoyed the long period of cool, moist weather of May and early June. Unfortunately, these same conditions were perfect for leaf spot disease activity. In most cases the grass plants leaf growth (all that mowing) stayed ahead of the disease. With the change to more stressful hot, humid weather the fungus weakened plants may suddenly brown and die.

Now with the onset of hot humid weather of late June and July, we are faced with another group of fungi. These fungi include melting out, Fusarium blight, dollar spot, and rust, as well as others.

Fungicides are generally more effective if used before disease symptoms appear or at the first sign of activity. Once you notice the damage it is very difficult to control the problem. 

There are of course, other factors that can cause symptoms that may be confused with disease damage. Always take the time to make a proper diagnosis before deciding on the proper treatment plan.

Hot, dry weather can result in activity of lawn damaging insects, such as sod webworm. The worm that does the damage is difficult to spot. It feeds at night and idles away the daylight hours in the thatch. The adult moth is about the size of a quarter and is tan to light brown in color. It can be seen flying in a zigzag pattern across the top of the grass. It flies only short distances and quickly darts back onto the tops of the grass. 

In addition to moth activity, a good sign of insects in the lawn is a large number of birds, particularly starlings and robins, feeding in the lawn. 

Prolonged periods of hot, dry weather favor a rapid buildup of these insects. They may produce as many as 3 generations during this time, resulting in widespread damage.    

Refer to Extension Fact Sheet 2011-95 for more information on how to identify the problem and to determine if treatment is necessary.

If you have not done so, raise your mower height at least one setting or ½ inch.  A good mowing height for the summer is 3 inches. The longer grass shades the soil and reduces moisture evaporation. The taller grass also is able to compete against weeds. It is still a good idea to mow off no more than 1/3 of the leaf at a time. Do not mow short and avoid scalping the grass!

Adequate water is essential to maintain a green lawn. If a quality turf is desired the lawn should be watered as soon as the grass shows signs of wilting. As the grass starts to run out of sufficient water, patches of the lawn will have a smoky tinge and turn a purplish, silvery blue color. The grass loses its bounce so footprints and wheel prints do not disappear quickly. These are indications of drought and will appear in sunny areas, such as south facing sloped areas, first. 

Apply enough water to moisten the soil to a depth of 6-8 inches, usually about 1 inch of water. In our heavy clay soils apply ½ inch of water at a time to avoid wasteful runoff.
That takes about 30 to 45 minutes with a typical sprinkler. Water until runoff is noticed then stop and allow the water to soak in before continuing. 

The best time to water is in the morning. Late afternoon or evening watering is best avoided if possible since it promotes fungus. 

Do I need to water my lawn? Cool-season grasses go dormant and turn brown during prolonged drought. Dormancy is the plants way of coping with a lack of needed water. Dormancy allows plants to survive these conditions for quite some time. A well-established lawn can survive many weeks of drought. While it may look unattractive the grass will usually recover with the return of cooler weather.

A new lawn, one less than one full growing season old, is more prone to damage from drought. If you have a newly seeded or sod lawn, it would be wise to consider watering during the first summer.

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All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Admin. and Director, OSU Extension TDD No. 800-589-8292 (Ohio only) or 614-292-1868

Revised November, 2001