How to Get Rid of Oleander Aphids

Oleander aphids can be controlled naturally.

The oleander aphid (Aphis nerii) lives on a diet of milkweed, scarlet milkweed, butterfly weed and oleander plants. Oleander aphids are not generally harmful to these plants unless their population is heavy. This insect releases a sticky substance called honeydew that can turn black with sooty mold. This is more of an eyesore to the gardener and less of a threat to the plant. Oleander aphids can be controlled naturally for a pesticide-free garden.

Things You'll Need

• Pruning shears
• Water hose
• Insecticidal soap
• Insecticidal oil

Instructions

1. Trim, water and fertilize your plants less often. These common plant maintenance routines have the affect of encouraging new tender shoots to grow. The oleander aphid prefers young tender shoots over established plant growth.

2. Dislodge aphids with a strong shot of water from the hose, or cut away and discard shoots that are heavily infested. You may not be able to eliminate all the aphids in this manner, but you will reduce the size of the colony.

3. Introduce an oleander aphid predator into your gardens such as the braconid wasp. The braconid wasp (Lysiphlebus testaceipes) will lay eggs inside the aphid, which will eat the aphid from the inside out.

4. Apply insecticidal soaps or oils directly to the pests for natural biological control. Insecticidal soaps have no residual or lasting effect and must be applied directly to the insect. Soap application is thought to break down the protective membrane of the insect, allowing excess loss of water and death. Insecticidal soap will need to be reapplied every four to six days until you are satisfied with the diminished population level. Insecticidal oils tend to suffocate the insect and will evaporate quickly, leaving very little residue.

Tips & Warnings

• Use the appropriate mixture of soap -- about 2 percent soap or 5 tablespoons per gallon of water. An increased concentration may be harmful to your plants and will not increase the number of insects killed.

• According to Colorado State University, commercial insecticidal soaps are preferred over homemade mixtures as they are specifically formulated to protect plants while killing pests.

• Some insecticidal soaps can kill beneficial predatory mites that help control spider mites.

• Insecticidal oil use can be harmful during times of drought when plants are under stress.

• Commercial insecticide or bug spray use is not necessary and can be harmful to plants, pollinating bees and butterflies.

References

• Texas A&M University: Oleander Aphid
• University of Florida IFAS Extension; Oleander Aphid; H.J. McAuslane
• Colorado State University Extension; Insect Control -- Soaps and Detergents; W.S. Cranshaw