While examining my milkweed, I noticed an unsightly black, sooty mold exclusively on the underside of leaves on my common milkweed plants. I knew immediately that aphids, a small 1/16- to 1/8-inch insect, commonly called plant lice or ant cows, had invaded.

Quite common and found on most plants, they cause little or no damage to the plant itself. However, with an aphid infestation, leaves become stunted, twisted and curled, with ants noticeably present.

Aphids are not easily seen but can be identified with the help of a magnifying glass. With a wide range of colors, long legs and antennae and a pear-shaped body, the most distinctive feature is a pair of tubelike structures called cornicles from the posterior of their abdomen, which produces an odor when alarmed.

Their sucking mouthparts ingest the leaf sap, causing the leaf to curl, producing a liquid called “honeydew,” a sweet substance that attracts ants, which eventually produces a black, sooty mold on leaves.

Because honeydew provides the sweetness for the ants, they in turn, care for the aphids. This is an example of symbiosis, in which two species provide a beneficial relationship. Other insects such as flies and wasps also enjoy the sweetness of honeydew, yet they do not damage the plant tissue.

Aphids can reproduce actively either sexually or asexually, giving birth to live nymphs many times during the spring and summer months. These nymphs will go through many instars (shedding of skin) during their growth period, which takes place in only 10 to 14 days.

Winged or wingless, they live on one plant or groups of plants, continuing the life cycle until fall, at which time they will lay eggs that overwinter and emerge once again in spring.

Living a somewhat complex life, the females that hatch in the spring are referred to as “stem mothers,” giving birth to live females that can reproduce asexually. Some aphids will reproduce throughout the summer, both laying eggs and giving birth to additional male and female aphids.

Aphid-infested plants are not usually damaged by their activity, but controls can be used safely without harming beneficial insects in the process.

The Ohio State University Extension recommends the following:

 A hard jet of water from a hose to dislodge aphids from the leaves;

 Select flowers and shrubs for your garden by observing which ones are resistant to aphids;

 Biological control with lady beetles, green lacewings or parasitic wasps, which are just a few suggested;

 If using chemical control, refer to the website below to ensure all directions are followed carefully, using integrated pest management practices.

Milkweed isn’t the only thing aphids attacked this year. The very dry conditions in late spring and into early summer allowed their populations to explode!

I hope next year’s gardens will not have as many aphids as this year. I can hope, but I will not plan on a totally aphid-free garden.

To see photos, control options, natural predators and more, check out this recent post: http://go.osu.edu/aphids .

Kane Shipka is a Master Gardener Volunteer for The Ohio State University Extension in Mahoning County.