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 susceptible
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
honeysuckle 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, so that they can 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 the honeysuckle aphids under control.
You can prune out infested terminals (ends of stems) where
overwintering eggs are found in early March. Seal the cuttings up 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.
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 of honeysuckle aphids.
Systemic insecticides labeled to control honeysuckle aphids 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.
A READER COMMENTS...
Using a systemic
insecticide on honeysuckle vines is like serving poison
to all the hummingbirds and butterflies that are
attracted to it. Hosing vines down regularly with a
fairly strong jet of water, or using a few drops of soap
in a sprayer is a much more responsible, kind solution.