What’s Causing Those Brown Patches in the Lawn? Brown patches can be a common sight in the summer lawn, brought on by causes ranging from bugs and drought to “self-inflicted” maladies such as dog-urine spots and fertilizer spills. But especially when summer heat joins with humidity or frequent rain, conditions are ripe for a variety of lawn-damaging diseases. The good news is that the arrival of cooler, drier weather often shuts down diseases and gives grass a chance to recover. A little reseeding in the fall might be all that’s needed. The downside is that diseases can recur year after year, sometimes killing the grass crowns as well as the blades and leading to larger-scale die-offs. This lawn suffers from lawn infestation - either induced by insects or fungus. Nycshooter / iStock / Getty Images Plus Where do lawn diseases come from? The fungi and other microscopic organisms that cause lawn diseases spread by wind, foot traffic, and shared lawn equipment. They lie dormant until the right weather comes along, which in the case of the four most common summer lawn diseases (dollar spot, brown patch, summer patch, and pythium blight) means damp, humid air and days above 85 degrees. Brown patches can pop up seemingly overnight. They’re usually irregularly round in shape, a few inches to three feet across, and can grow together to cause widespread brown areas. What to do about lawn diseases There’s not much you can do about humidity and hot weather, but you can take steps to make your lawn less inviting to disease. Avoid wet grass by a.) watering the lawn only when necessary; b.) watering deeper and less often (i.e. three to four days apart instead of daily); c.) watering in the morning instead of evening when the blades dry quicker, and d.) monitoring automatic timers so they don’t come on even when rain has done the deed for you. Planting or overseeding with grass varieties that are naturally more vigorous and disease-resistant, such as the types selected for GreenView Fairway Formula grass mixtures and blends. Apply good practices that keep the lawn as healthy as possible, including mowing high, keeping mower blades sharp, aerating and top-dressing to improve soil drainage, controlling thatch, and asking mowing services to disinfect equipment before mowing your lawn. Brown patches like these in the summer lawn are often caused by one of several heat- and moisture-loving diseases. George Weigel Adequate fertilizer also is important, but keep in mind that more isn’t better. Although lack of nitrogen is a key factor behind outbreaks of dollar spot, excess nitrogen can encourage summer patch, brown patch, and pythium blight. The trick is to give lawns enough fertilizer to encourage good growth without over-doing it. One way to do that is leaning toward slow-acting fertilizers that break down gradually and feed over a longer period of time, such as those in GreenView’s lineup of lawn fertilizers. Or sign up for a GreenView Annual Lawn Plan in which the right products for your lawn are shipped at the right time throughout the growing season. What about bad outbreaks? Lawn fungicides are available to slow the progression of lawn diseases, but they’re primarily effective at preventing outbreaks and their spread rather than curing diseases. Different ones are more effective than others, depending on exactly which disease you have, and they have to be applied correctly to work best. That means researching to identify the cause of your patches and reading labels before applying any product – or calling in an expert. If dollar spot has infected your lawn, fertilizing with a high-nitrogen product will often fix that as opposed to using a fungicide.