Which of the following diseases is known to cause "damping off" in turfgrass?

Damping off is a term used to describe a range of fungal diseases that affect seedlings, causing them to rot and collapse at or just below the soil line. In turfgrass, one of the primary causes of damping off is Pythium blight. This is a water mold that thrives in warm, wet conditions and can rapidly kill turfgrass seedlings, especially when they are stressed. In addition to the typical signs of damping off, Pythium blight can lead to large areas of blighted or dead turf.

While other diseases like leaf rust, red thread, and dollar spot affect turfgrass, they do not specifically lead to damping off in seedlings. Leaf rust and red thread primarily cause discoloration and patchy damage in established turf, whereas dollar spot results in circular spots of dead grass. None of these diseases are associated with the pre-emergence or early-stage seedling mortality that characterizes damping off, making Pythium blight the correct choice in this context.