Fruit flies and their larvae do not damage the coffee seed. The fruit fly adult pierces the coffee berry skin and lays her eggs between the skin and parchment of the seed. The piercing and resulting maggots causes damage to the skin and pulp, but does no damage to the parchment, or green bean/seed.
Pre-mature ripening and berry drop can occur, but as a whole, fruit flies do not cause significant damage and do not typically warrant control unless neighboring edible crops are affected.
Fruit fly management: