Yellow jackets can deliver painful stings when you're working in or around your garden and can ruin outdoor events. Natural repellents can help prevent potentially dangerous yellow jacket stings and come in the form of citronella or wormwood. However, you will most likely need to trap wasps to keep the populations down. Citronella oil is typically used as a repellent for flying insects and may be effective against yellow jackets. Citronella can be purchased as a candle and contains citronella extract, a type of plant. The aroma of the citronella will disperse when the candle is lit, keeping many flying insects away. Wormwood is the only plant currently thought to repel yellow jackets, according to Ask the Exterminator. Plant a sufficient amount of wormwood around your home or garden to act as a deterrent. Natural yellow jacket repellents may not always be successful and the most effective way to avoid yellow jacket stings is to prevent them. Yellow jackets are wasps and eat meat during the summer months, so keep meat tightly covered when it's outside. During outdoor picnics, keep eating areas at least 20 to 30 feet downwind of a nest so that the yellow jackets cannot smell the food. Trapping yellow jackets may be the best way to reduce populations since the success of natural repellents varies. Traps can be made out of soda bottles with the tops cut off and then pointed down into the bottle's body, creating a funnel down into the bottle. Place water and meat at the bottom of the bottle, and the yellow jackets will fly down through the funnel toward it. They will then have a difficult time getting back out, trapping them. Some people may think that the best way to get rid of yellow jackets is to destroy their nest. Never tamper with a wasp nest under any circumstances. Yellow jackets are extremely territorial and aggressive. Tampering with their nests will invoke an attack that could result in serious injury or even death. Consult a professional exterminator if you want to remove a yellow jacket nest from your property.