Dahlia Aphid Control

Features

• Aphids attack the foliage and stems, sucking juices from the plants. Look for aphids on plant tips and the underside of leaves. A few scattered insects first appear, followed by aphid clusters that stunt the plants, causing curled or warped leaves. As the aphids feed on the juices, they suck out more than their bodies absorb. The excess is secreted as honeydew, a sticky substance that spreads diseases like sooty mold harmful to the dahlias.

Cultural

• Check for aphids when dahlias are young as aphids attack tender plants. At the first sign of aphids, spray them off with water. Most aphids will not return. This forcible removal controls light infestations. Some gardeners vacuum off aphids, whiteflies and other pests. Look for nearby weeds or plants that are host plants for insects. Remove these aphid hosts. Encourage aphid predators such as ladybugs that eat aphids. Natural predators consume hundreds of aphids, but are not effective against large infestations.

Organic

• Use organic sprays for continued infestations. Spray insecticidal soaps that are nontoxic but disrupt the insect's cell functions. These soaps typically contain potassium fatty acids that kill insects on contact without leaving residual poison. Control aphids with insect sprays or powders containing pyrethrins or rotenone. Pyrethrins are organic compounds derived from chrysanthemumlike plants. They attack the insects and have a mild residual effect as the compounds decompose. Reapply as directed on the label. Rotenone sprays, derived from certain shrubs and roots, effectively control aphids. The plant extracts break down quickly in the environment, but should be handled with caution. Follow label directions carefully to avoid skin and inhalation irritation.

Chemical

• Control heavy or continued infestations with chemical insecticides. Some slow-release granules, worked into the soil, provide both fertilization and insect control for the growing season. Many products for roses and other flowers are labeled for dahlia use. Use chemical insecticide sprays and powders by applying them on all surfaces of the plant, particularly the underside of leaves. Check the label to be sure the product is appropriate for dahlias. Used as directed, these insecticides are effective against a broad range of dahlia insect pests.