Answer: What you describe sound like fungus gnats. They are living and breeding in decomposing organic matter at the soil surface. They thrive in moist places so beneath the decorative rocks the soil is damp. Generally the rocks will serve as a barrier between the gnats and the soil so perhaps you should add more decorative rocks to the area to make a thicker barrier. The gnats do not feed on plants or lawn and they won't bite you but if they are bothersome you can use an insecticide to kill them. Bayer Advanced? Complete Insect Killer For Soil & Turf is one of the treatments you can find in your local garden center. Mosquitoes are also attracted to standing water so the additional rocks should control mosquito breeding in the area. Good luck with your landscape!
Q&A Library Searching Tips