Q.Why Are House Flies Eating My Basil Plants.
Flies hate basil, that’s a crock! Just bought 2 basil plant for my kitchen. Both plants have swarms, b/w 5 and 10 flies on each plant, opposite side’s of the kitchen. Holes in every leaf. Why????

Certified GKH Gardening Expert
Houseflies do not normally eat plant leaves so something else is probably eating your plants. Since your plants are indoors that limits the insects. Check the underside of leaves for common insect invaders such as aphids, scale, or whiteflies, that may have come with your plants. Those are sap sucking insects whose holes are likely too small to notice, however. Fungus gnats fly around plants but they are not eating the plants. Sometimes holes are caused by fungal spots that drop out.
You can safely spray basil with insecticidal soap. You also can place yellow sticky traps around the kitchen.
https://extension.colostate.edu/docs/pubs/insect/05502.pdf
https://hgic.clemson.edu/factsheet/less-toxic-insecticides/
https://www.gardeningknowhow.com/edible/herbs/basil/holes-in-basil-leaves.htm
https://www.gardeningknowhow.com/edible/herbs/basil/basil-diseases.htm