Lysol floor cleaner. Not organic, but it is cheap & works fast. I just know it works well for me, & seems stronger than 'lemon dishsoap'. Repeat water diluted spray, at least every week till gone. If you don't do something those chiggars will eat you alive, and they will spread to other areas, and they will come back summer after summer, and as you know, they will ruin your outdoor
experience. Try NOT wearing white clothing, as it attracts them. I have put up 'sheets of white plastic' like a
fence, then spray the
fence. I typically use one of those water hose garden spray applicator and spray the whole
yard with the Lysol. Try to just apply on the surface layer of the compost heap, I think the chiggars mainly hang out on the surface layer. The red cedar around the yard is good, but easily catches fire or smolders if lighted, don't mix it in your compost, it repels the best bugs that you need in the stuff. Perhaps a thick red cedar pathway around your compost pile, probably slow the biters down at least on the pathway, mix a few small stones in the cedar so it doesn't blow away.
james beam;)