It’s not so much the flies themselves that cause the problem, but the larva they lay inside the young, immature berry. These berries rarely grow into the full luscious berries we all love. In case you’re wondering though, Don Miles said even if you eat these berries with the larva, it will not harm you. They are very small, and usually only seen through a magnifying glass. Riggs said the best way to test for them is to pick berries near the ground, put them in a black plastic container, fill with salt water and squeeze the berries. The salt water will draw the larva out.