What Can Take Away Aphids on Shrubs?

Aphids

• Aphids use needle-like, piercing mouthparts to suck the sap from newly emerging leaves and flowers. Their feeding causes deformed and distorted growth as well as yellowing and stunted growth. As they feed, aphids excrete a sticky, sweet substance called honeydew. This substance can trap dust, plant matter, dead insects and other debris, giving the plant an untidy appearance. Honeydew also feeds a fungus called sooty mold. The black, powdery mold covers plants as it feeds on the honeydew, shading leaves and preventing photosynthesis.

Natural Enemies

• Many natural predators eat aphids and are quite effective at keeping their populations in check. The ladybug is perhaps the best known, but other predators include lacewings and a number of syrphid flies. Parasitic wasps are also known to lay their eggs in aphids' bodies. Protect these natural predators by limiting or avoiding the use of broad spectrum insecticides.

Cultural Control

• For small or isolated populations, squish aphids as you see them; wear gloves if you're squeamish. Prune out heavily infested branches and throw them in the trash. Knock aphids off plants with a strong jet of water. They are not good climbers and will die in the soil. This method is also effective at killing eggs. Spray aphids with water in the morning so wet foliage can dry before temperatures cool down at night. Cool temperatures and wet leaves foster fungal growth.

Chemical Control

• If cultural methods are ineffective at controlling aphids, you may need to resort to chemical control. Insecticidal soaps and horticultural oils are generally less harmful for beneficial insects and are recommended by the University of California for aphids. Mix a few drops of mild, unscented liquid dish soap in a spray bottle of water to make your own safe insecticide. Spray plants weekly during the spring and summer.