The dusty blue coating on blueberries is not dirt; USDA researchers say the wax helps defend against disease and prevents the fruit from drying out after harvest

The dusty coating on blueberries is a natural protective wax. This bloom shields the fruit from disease and prevents drying out. Researchers are studying this wax to breed hardier blueberry varieties. Anthocyanins, which give blueberries their color, offer significant health advantages. Washing blueberries just before eating preserves their natural protective qualities.