So I'm working on building a raised garden bed in my yard. This bed is adjacent to an area where I have completely killed the grass last year. I had raked off the dead grass and saved it off to the side to use as a top dress. As I was working on the wall around the bed, the top dress stuff was in my way, so I started to rake it out. What I found was about 100 grubs spread out over about 10 feet. They did not penetrate into the soil, just in the topdressing. Needless to say I had fun squishing grubs. The ants got at least one and hopefully the birds got some too.
Why in the world would they only be in the top dressing. Is my soil so hard that they can't get in or is it an organic matter issue.