Aphids are also called "plant lice." They infest both annuals and perennials, and their infestations begin in early spring and last until late into the fall season. Garden phlox (a popular perennial and old time favorite among gardeners) are susceptible to aphids. Generally, aphids do not cause much damage to the plants.
Phlox plants are also called garden phlox and tall phlox. Depending upon the variety, they can reach heights from 15 to 48 inches, with a clump size from 24 to 36 inches. They can be planted in sun or partial shade, and they require well-drained soil. The clusters of trumpet shaped blossoms are extremely fragrant and long lasting. Their blooms appear in mid-summer and colors range from lavender, pink, orange, red, salmon, scarlet and white. The flowers of some cultivars are also bicolored. These lovely perennials are hardy from zone 3 through 9.
Pests and Diseases
Aphids are not the only pests that feed on Phlox. Beetles, caterpillars, grasshoppers, leafhoppers, leaf miners, spider mites, and whiteflies may also infest phlox, although they usually do not cause much damage to the plant. Possible diseases include: powdery mildew, fungal leaf spot and stem canker diseases. The most common is powdery mildew, so plants should be spaced far enough apart to allow air circulation in order to avoid the occurrence of powdery mildew. You should also avoid wet foliage. This can be done by watering at the base of the plants and by watering the plants early in the morning so that the flowers and leaves will have time to dry out in the sunlight.
Aphids are about 1/8 inch in length or smaller. They use their sucking beaks to suck the sap out of the plant. These small insects give birth to their young in the spring and summer months. You will find young as well as mature aphids feeding on the same plant. Some species of aphids have wings and others do not. The aphids that attack phlox and most other garden plants are wingless. There is a species of aphid that attacks almost every variety of flowers grown in the garden. Most aphids congregate on the underside of the leaves of the plant.
If the phlox plant is infested with aphids you will notice stickiness on the leaves of the plant and there may even be some leaf distortion. Aphids suck the sap from plants and can cause some of the leaves to curl up, wilt or die. As the aphid feeds, it excretes honeydew (a waste material). Honeydew looks like a sticky substance that is left on leaves. It attracts other insects such as ants, yellow jacket wasps, flies and bees. Honeydew also creates another problem: sooty mold. The honeydew is a base on which sooty mold forms and grows. If there are large amounts of aphids on the plant, then there will be large amounts of honeydew, which may lead to sooty mold growth.
The natural enemies of aphids are lady beetles, flower fly larvae, lacewing larvae and parasitic wasps. In most cases, these natural enemies will take care of the aphid problem, and you may not even be aware of the presence of aphids. Aphids can be controlled by the use of insecticides or insecticidal soaps. You can also remove them from the plant by spraying the undersides of leaves (where they congregate) with a strong jet of water.