SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/37461
Q&A Unwanted mowing pattern BY DR. DAVID MINNER Professor, Iowa State University Questions? Send them to David Minner at Iowa State University, 106 Horti- culture Hall, Ames, IA 50011 or email dminner@iastate.edu. Or, send your question to Grady Miller at North Carolina State University, Box 7620, Raleigh, NC 27695-7620, or email grady_miller@ncsu.edu. Q We get a lot of nice comments on our mowing pattern but this happened to us last week when it was really hot. What’s up with the wheel tracks and how do I prevent it from happening again? Iowa City The problem is Ascochyta Leaf Blight that is almost always trig- gered by high temperature and rapid drying conditions. The most difficult part of this disease is pro- nouncing the name Ascochyta when you are trying to talk about it to your boss, so it goes like this: “ass-co-kite-a.” Just Google “as- cochyta turfgrass” and you will get lots of good general information that I will pick apart for you in this column. The fungal spores called conidia grow and are splashed around dur- ing periods of frequent rain or irri- gation. The organism may be present from late spring through the summer, but it usually begins the leaf blight phase only after a period of suddenly hot weather. Predicting an Ascochyta outbreak is difficult because the exact condi- tions for blighting are not clearly understood and the disease symp- toms appear haphazardly through- out the summer. When the conditions are right the bleached and blighted leaves will suddenly appear. One day the grass looks fine and then suddenly you have lots of tan grass and clearly defined mowing streaks in just a day or two. The mowing streaks probably abrade the grass allowing easy entry of the infec- tious spores into the plant. Look for bleached leaf tips that are collapsed. It looks devastating because the top part of the plant is severely damaged but the crowns and lower stems are seldom killed. The good news is that you can an- ticipate 80-100% recovery within 3 weeks, but in severe cases some 50 SportsTurf | August 2011 www.sportsturfonline.com turf loss may require reseeding. Taller and less frequent mowing is recommended but most of you are locked into mowing schedules based on field use and perform- ance. It is interesting to note that Ascochyta blight in home lawns will only occur in full sun areas and it stops where the shaded lawn has less heat stress. In my 40 years of messing with grass I have never seen it as bad as it has been in the past 2 years in Iowa. Normally we don’t recom- mend a preventative fungicide be- cause it occurs to haphazardly and a curative fungicide doesn’t help after the leaf tissue is blighted. However, after 2 years of seeing this occur in late June and early July on the same fields I will be ap- plying a preventative fungicide trial next year in mid-June to see if con- trolling the fungus will reduce the wheel tracking injury. I have mowed plenty of grass that is wilted during hot condi- tions without seeing any wheel tracking so I guess it is the combi- nation of fungal presence, hot weather following frequent rain or irrigation, and mowing at the wrong time that all lines up to give a mowing pattern that you re- ally don’t like to see. Even if you don’t have a nice striping mower try to mow nice straight lines… at least you can brag on your mow- ing talent if Ascochyta comes to town. ■