Q. Something has spoiled the flowers and some of the foliage on my 'Gold Flame' honeysuckle vine. They look black and kind of sticky. Can you tell me what this is and how to get rid of it?

A. Honeysuckle aphids (Hyadaphis foeniculi) are the most troublesome pests of ornamental honeysuckle vines (Lonicera spp.).

Their feeding damage spoils the flowers and causes the leaves to become distorted and curled.

Aphids feed with piercing-sucking mouthparts and inject a toxin or plant growth regulator as they feed that causes the curling and distortion.

Their feeding damage can cause witches' brooms -- an abnormal tight cluster of growth -- to form in some Lonicera species.

The black stuff you see could be sooty mold that is growing on aphid honeydew, a polite term for insect excrement. Because they feed in the plant's vascular system -- specifically the part that takes carbohydrates produced in the leaves through photosynthesis to the roots for storage -- their excrement is sugary and sweet.

Honeydew is an ideal substrate for sooty mold to thrive. Although it is unsightly, sooty mold does no real harm to plants.

Honeysuckle aphids have several generations a year, so repeat applications of an insecticide are usually required to keep them under control.

They overwinter as eggs on the tips of shoots, twigs and stems. The aphids that hatch in the spring as honeysuckles leaf out are all female and are known as stem mothers. They give birth to live young (also all female). These first-generation offspring feed on new shoots and the underside of the leaves.

The second and additional summer generations feed on the upper side of the leaves.

In late summer or early fall, a generation of winged males is produced. They mate with the females and produce eggs that will survive winter. The following spring, the cycle starts over again.

Try a couple of tactics to get honeysuckle aphids under control.

You can prune out infested terminals (ends of stems) where overwintering eggs are found in early March. Seal the cuttings in a plastic trash bag or burn them if permitted.

Once honeysuckle aphid eggs hatch, adults will fly in and re-infest the plant, so pruning alone is not enough to provide effective control.

In late spring before the plants leaf out, apply horticultural oil as a dormant treatment. The oil will suffocate many of the eggs and reduce the population of overwintering aphids. This is NOT dormant oil. Horticultural oil is more refined and less injurious to sensitive plant tissues.

Scout the plant regularly through the growing season and use a summer or growing season rate of horticultural oil (1-1.5 percent) whenever you notice their activity.

Horticultural oil works only on contact, so be sure to get thorough coverage under the leaves where initial colonies develop. Horticultural oil has the added benefit of being soft on beneficial insects and pollinators because it only affects insects in direct contact with the spray. Once the spray dries, it has no residual activity. Avoid applying horticultural oil to drought-stressed plants. You can irrigate thoroughly the night before spraying if necessary. Also avoid applying horticultural oil when temperatures are 90 degrees or above or when humidity is very high to minimize damage to plants.

Other contact insecticides labeled to control honeysuckle aphids include: BioNeem (azadirachtin), Bayer Advanced Power Force Multi Insect Killer (cyfluthrin), malathion and pyrethrins plus piperonyl butoxide. These products will require repeated application to achieve satisfactory control.

Systemic insecticides include Orthene (acephate) and Bayer Advanced Tree & Shrub Insect Control (imidacloprid or Merit insecticide).

While systemic products do not have to be applied as often as contact insecticides, they can pose more of a risk to beneficial insects and pollinators.

First Published: July 2, 2011, 8:00 a.m.