I’ve been reading about your chicken’s beetle problem and I’m wondering if beneficial nematodes would help. If the beetles have a life cycle stage in the soil they should kill the beetles in the larval stage in the ground.
Available from arbico organic.
I have used the nematodes on my property and had good results. Fewer Japanese beetles and ticks. They also kill flea larva and a large group of soul borne pests. They do not harm earth worms.
The nematodes infect the larvae and reproduce inside the host, then come out and look for another victim. I propagated them in wax moth larvae.
When I got the nematodes I suspended the nematodes in non chlorinated water (a gallon or more trying to keep temperature of water and nematodes similar) then putting them into a quart spray bottle and squirting them over the ground. Have the spray mechanism wide open and spray in an arc. Shake periodically to keep the nematodes suspended.
It is best to apply them in the rain so they get washed into the soil and can go right to work. If you have a sprinkler or garden hose, water them in well after application.