Lemons And Cloves Might Be All You Need To Solve This Common Kitchen Problem - Tasting Table

"Before plug-in repellents and neon flytraps, kitchens kept their own food-safe line of defense. Lemons studded with cloves have been set around and hung in pantries for centuries. They look decorative, almost festive, but they're performing a valid service backed up by chemistry. Citrus peel releases limonene, and cloves contain eugenol, two volatile oils that flies can't stand due to their sensitive smellers, as they use odor to help navigate."

"Recipes for clove-studded fruit, called pomanders, appear in European manuscripts from the Middle Ages, when folks pressed cloves into oranges or lemons to perfume clothing and ward off illness. Kitchens kept the habit long after the plague left town, probably because it's cheap and effective. A halved lemon pierced with a few cloves works in the same way those pomanders did: the volatile oils in the spice slightly preserve the fruit, keeping it fragrant longer."

"Making one of these fly-keep-aways is about as easy as it gets. Slice a lemon in half or into thick rounds, press whole cloves onto the surface, and leave it somewhere that attracts gnats or fruit flies. As the lemon dries, its surface releases limonene vapor, and each clove (wetted and activated by the lemon juice) leaks eugenol. The smell might be strong at first, then mellows to a subtle, resinous, clean background aroma. You'll know it's time to replace it when it shrivels completely"

Lemons studded with cloves function as a natural fly repellent because citrus peel releases limonene and cloves emit eugenol, volatile oils that overwhelm insect olfactory hairs. Flies rely on odor to navigate, and the combined aromas create an aromatic miasma that disrupts their ability to locate food. Recipes for clove-studded fruit, called pomanders, date to the Middle Ages, when people pressed cloves into oranges or lemons to perfume clothing and ward off illness. A halved lemon pierced with cloves remains fragrant and slightly preserved by the oils for several days before drying. To use, slice or halve a lemon, press whole cloves into the surface, and replace when shriveled.

Read at Tasting Table