Answer: Flies are not usually attracted to rocks, unless water is pooling under the stones and the flies are looking for water. There's really nothing you can spray to deter the flies so you might want to investigate the mulched areas to see what is attracting them. If water is pooling and stagnating, you may have to either rinse the stagnate water out, or rearrange the rocks so water doesn't collect beneath them. Hope this helps!
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