Purdue News

June 26, 1998 It's too wet for some lawns, Purdue expert says WEST LAFAYETTE, Ind. -- The rain doesn't always make the grass grow faster -- sometimes an overabundance of water causes lawn problems, says Zac Reicher, Purdue University Cooperartive Extension Service turf expert. Reicher said wet weather can bring turf diseases, but the most serious problem is caused by standing water. "Turfgrasses can easily withstand submersion for up to 60 days when water temperatures are 50 degrees or less, but they can be killed in as little as one day when water temperatures are 86 degrees or higher," Reicher said. "The injury is greater if the turf is under stagnant water instead of moving water." According to Reicher, the amount of damage will vary with the type of turfgrass. "Of cool-season turfgrasses used in Indiana, creeping bentgrass is the most tolerant of submersion, Kentucky bluegrass is less tolerant, and annual bluegrass and perennial ryegrass are the least tolerant," he said. To improve recovery of flooded turf, Reicher suggested removing the water as quickly as possible by pumping it off the lawn, cutting drainage swales, or pushing it off with squeegees. Reicher said that after the water is moved off of the lawn, the homeowner should immediately remove any debris, silt, or sand. "Consider raking the lawn regularly to keep any remaining crust broken up throughout the season." he said. "If the grass is not green after the water recedes, and does not green-up within a week or two, consider vigorous aerification followed by reseeding." In addition to problems with submerged turf, Reicher said these lawn problems also may occur during wet summer weather: Yellow patches: "With the monsoon-like weather that we have had in Indiana the past two weeks, yellow patches two or more feet in diameter are beginning to show up in turf areas," Reicher said. "Although there might be a number of causes for this, the likely cause is saturated soils with no oxygen available to the roots." Reicher said there are no-short term solutions for this problem. "To help prevent this and other water-related problems in the future, try to improve surface drainage to move water off site," he said. "Improving underground drainage with tile can also help." Reicher added that after the soil dries, aerification will help by reducing soil compaction, improving oxygen movement in the soil and improving drainage. Mushrooms: Extremely wet weather combined with warm soil temperatures will cause mushrooms to sprout in the lawn. Reicher said these fungi come in many sizes, shapes and colors. "These mushroom are naturally occurring, and unfortunately there is no good way of controlling mushrooms other than regular mowing," he said. "No fungicides are labeled for mushroom control." Reicher said that mushrooms thrive in wet areas, so improving drainage and air flow over a turf area (by cutting shrubs, pruning trees or cutting weeds) should help to prevent mushrooms over the long run. Red thread and dollar spot: With the saturated soils and humidity, the plant diseases red thread and dollar spot are appearing in lawns in Indiana, Reicher said. Red thread appears as small spots on the grass leaves that are the size of a quarter or a golf ball and colored purplish-blue, eventually turning tan. A distinctive red or coral colored "thread" is often seen growing from tips of infected leaves. Dollar spot shows up as small, light tan lesions on the grass blades, usually shaped like an hour-glass with reddish brown margins. "Often you may see what looks like spider webs or cotton candy on infected leaf blades in the morning, especially after a very warm, humid evening," Reicher said. Both diseases can kill the grass plants that they infect. As with all diseases in home lawns, he said, the most effective way to control the two disease is with good lawncare practices. Reicher suggested mowing the lawn 3 inches high or more, watering deeply and infrequently, and applying proper fertilizer, with the majority of fertilizer applied in the fall. "These are the best ways to prevent any lawn diseases," he said. Reicher said that red thread and dollar spot are indicators of low nitrogen, and homeowners who spot these problems should consider applying nitrogen fertilizer to the lawn if it has not already been applied in the previous month. To combat these diseases, Reicher said to apply three-quarters of a pound of nitrogen per 1,000 square feet of lawn. "However, there are other diseases that will thrive under high nitrogen, so do not over-apply," he said. "You should use mostly slow-release nitrogen, which on the label will appear as sulfur- or polymer-coated urea, urea formaldehyde, methylenediurea, dimethylenetriurea or natural organic nitrogen." For the majority of homeowners, fungicides are not recommended. "If a fungicide application is desired, contact a lawn care professional to do the job," Reicher said. Source: Zac Reicher, (765) 494-9737; zreicher@dept.agry.purdue.edu; https://www.agry.purdue.edu/agronomy/turf/zjr-bio.htm Writer: Steve Tally, (765) 494-9809; tally@purdue.edu; https://www.agcom.purdue.edu/AgCom/homepages/tally/ Purdue News Service: (765) 494-2096; e-mail, purduenews@purdue.edu To the Purdue News and Photos Page