Fungus Gnat: It looks like cutworm damage, but it is not

Sometimes we like to post questions or concerns that come from the field. Dr. David Shetlar, Professor of Turfgrass Entomology at The Ohio State University shared the following pictures and question that he received from a golf course superintendent in Portugal.

Question: Dr. Shetlar on our greens it looks like we are getting some cutworm damage (Photograph 1), but when we sampled we found the following (Photograph 2), are these different larvae stages?

Answer: Neat!! These are the actually the larvae of one of the fungus gnats! They often get up and move in mass like this after a rain. The clear larvae with white fat inside and black head capsules normally feed on decaying organic matter (like the thatch) and when they are ready to pupate, they often travel several meters to find a dryer location. The little black flies with long legs will emerge 10-14 days later. The adults don’t normally feed, but some may take nectar from flowers. The adults will again lay eggs in moist, decaying plant material.

We have never seen them cause damage to the turf and most entomologists would consider them a beneficial agent for decomposing the thatch.