This information is quoted from the Turfgrass Management book ,by A.J Turgeon
"Close examination of the turf,especially after brushing accross the shoots
with the fingers,reveals the tiny Chinchbugs where feeding takes place."
"Another diagnostic technique is ti insert an open-ended cylinder,
(coffee can,with both ends cut off) into the turf,fill it with water and add pyrethrin or household detergent:if present,chinchbugs will float to the surface in 5-10 minutes.
Do the "tug test" for Bluegrass billbug damage. If the grass comes out with an easy tug, look at the ends to see if they are hollow and filled with sawdust like material indicating Billbug damage. We had a tremendous amount of damage here in the late spring.