Install a Pest Pool
Use 4 litre plastic bucket buried with top level with surrounding garden contour,
fill with water to inch below top of bucket,
place 2 parallel sticks ( sticks 1/2 inch wide and flat) place the 2 sticks parallel a couple of inches apart , across the bucket ( sticks to be pretty much even with dirt)
The dirty little SOB's for some reason can't resist falling into the water and they do not paddle water for long,
And it works 24/7 , replace water every few days, even if there is already a " floater in the pool" more others will take the plunge,,,,