Basic sod maintenance is the best disease prevention program. Specific maintenance practices include proper fertilization, correct irrigation (watering and drainage), correct mowing height, appropriate maintenance tools, placement in full sun, and use of disease resistant sod. While full sun placement isn't always possible, it is important to keep in mind that a lot of shade isn't ideal as the grass is more thin, weak and prone to stress. Weather also plays a huge part in the outcome of your turf, and it's unpredictability and uncontrollable nature will often work against you.
Diseases in lawns usually start small with a few patches or spots. If a problem is severe and widespread and has occurred suddenly, there's a good chance it is not a disease but another stressor caused by heat, water, mowing, poor drainage, or fertilizer, just to name a few. Irrigation problems are often the root cause of discolored lawns. Providing good soil drainage and maintaining proper irrigation are crucial steps in preventing many sod problems.
If the cause of the turf problem is a fungus, there are different types of fungicides that are meant to be used either preventively or curatively. Preventive fungicides work to activate a plant's natural defenses against infection. Curative fungicides can stop dead or diseased areas from getting bigger, but will not bring a dead patch back to life. It will take time for the grass to fill back in on its own, or it can be re-seeded. It can be helpful to keep a record of where the disease has occurred as fungus often occurs in the same areas year after year, so preventive fungicide can be accurately applied. Prevention is always best, which will include applying preventive fungicide, aerating, proper fertilization and irrigation maintenance.
The most common summer disease found in grasses like tall fescue is brown patch. It creates large, tan-colored lesions on the blade of grass and expands into circular patches up to several feet wide. Brown patch is most aggressive when there's a combination of high humidity and temperatures above 90 degrees, but can also become active when temperatures at night are above 60 degrees, thus being active through summer and well into September. Preventive fungicides are the best option for brown patch when applied in the spring or early summer. Large patch can be found in warm-season grasses like St. Augustine. Tan or red-brown lesions can be seen on the leaf sheath and expands into circular patches, oftentimes 12 feet wide. Large patch attacks when warm-season grasses are growing more slowly, during fall, winter and spring. It becomes active when temperatures drop below 60 degree, which is the ideal time to apply preventive fungicide.
A common type of pest that can be found in your turf are grubs. A preventive insecticide for grubs is best done in June and July as this will protect your lawn through the end of mating season in August. This preventive insecticide should provide control for up to four months. In the spring or fall you can apply curative insecticides that control current problems, but will not prevent future problems.
While there are preventive and curative fungicides and insecticides that will treat turf diseases, it is important to reiterate that proper lawn maintenance and preventive practices are the best approach when caring for your sod.