Most birds do very well at eating their share of bugs. Like the birds that eat them the majority of local insects are harmless, but recently the area has experienced an pandemic Lyme Borreliosis or (lymes disease) which is carried by ticks and hosted by you!! Lymes can be FATAL if left un-treated.ground birds like guinea fowl , chickens, turkey, ect... forage all day long looking for small insects to eat. A guinea is a ticks number one enemy and favorite food,birds in general are humans first defense against Lymes wet winters like this past one seem to increase the tick population.
I do not use , recommend or endorse the use any fertilizers or insect repellent around your flock the only thing that is recommended by others is sevins dust which is safe to use around animals . wasp and bee killer can KILL your birds and should never be use around your flock. I've heard guineas sitting outside of bee hives and eating every last bee until the hive is empty. Turkey also do a very good job helping your garden eating slugs and other critters that can be harmful to your plants at the same time providing fertilizer.