Not necessarily, all it takes is for the mite to walk over an area that has the residue on it and that will kill them. They use it in poultry houses and they just spray it in rows so when the mite walks over it they die, but same with any other bug even flies will die because my whole covered run area I have screened over the hardware cloth so that mosquitoes can’t get at them at night and so I can spray it inside and it sticks to the screening and every insect that comes in contact with the inside of their covered run dies. I try to be very careful with it because of the bees.Glad you mentioned about being careful because I don’t want to kill any of the good bugs like bees and butterflies.. if I have windows in the coop would you recommend maybe putting tint on them to filter the sunlight?