This mystery comes from a putting green in Spain. The grass is Penn A-4 creeping bentgrass. One can see at the corner of the green a mark from the triplex mower as it makes the cleanup pass. And diagonally across the green, there is this line of damaged grass. Here is a closer look at the mysterious line.
Can you identify the cause of this line on the green?
Greg Austin was the first to identify this as an ant trail across the green:
@asianturfgrass if animal damage is close, my next guess would be damage from insects. Possibly ant damage. From a trail?— Greg Austin (@bcgolfsuper) December 16, 2013
Steve Agin also correctly identified the cause of this line. Getting closer to ground level on the green, one can see that this is an ant trail. Thanks to David Bataller for sending the photos for this turfgrass mystery.