Question
QUESTION: Hi Jim--I read with interest your answer to someone about aphids leaving a sticky substance from there digestion of oak leaves.  We park our cars in the driveway under an Oak (owned by our neighbors, but overhanging our yard)--and they get covered in a fine sticky mist.  There seem to be a lot of wasps flying around the leaves--but I haven't noticed aphids.  Do you think there are aphids (which I just can't see high above me)--and the wasps are also attracted to this stuff?  Many thanks!  Jane

ANSWER: Yes it sounds like aphids. And wasp will come to the sugar as they will to humming bird feeders. The aphids are small but it could also be scales insects they both secrete honeydew and give the sticky mist effect. Both can be treated with insecticides.

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QUESTION: This is very helpful--and you were so fast!  Thank you--I just gave you a perfect 10 rating.  It didn't occur to me before to ask-but will the aphid problem go away once it is winter and the leaves have fallen?  That is, if we do nothing, will it happen again next spring?  The area around/under the oak has a lot of hostas, day lillies and other plants--will treating the ground soil affect those plants adversely in any way? The tree is quite large--not sure how practical it will be to treat all the leaves.  Are there any other options to deter aphids (planting catnip?--or would that be insignificant)?

Answer
Will it go away in the winter--yes and no. The leaves will fall and the feeding will stop during cold weather but the aphid will over winter as eggs and hatch out in the spring.  Most species of  aphids overwinter as eggs on specific types of woody plants. Eggs hatch in the spring. The following spring and summer, forms of the aphid sometimes move from overwintering plants to other plant species. Summer aphids consist entirely of females that give birth to live young at a rate of one to 20 per day.

The newly hatched aphids can complete their development within one to two weeks, after which they begin to produce more aphids. Consequently, aphid populations may increase rapidly, with several generations occurring during the growing season. At the end of the summer, both male and female aphids are produced. They mate on the overwintering host plant, and females lay eggs.

Many kinds of insects naturally prey upon aphids. Most common are various species of lady beetles (ladybugs), green lacewings, syrphid flies and small parasitic wasps. Under many conditions, these beneficial insects provide effective control of aphids. Before applying any insecticide, check the plants to make sure these natural controls are not already reducing aphid numbers. Sometimes ants interfere with these natural controls. Excluding ants with sprays, sticky bands, etc., can allow biological controls to be effective.

When natural enemies are not abundant enough to provide aphid control, insecticides sometimes are needed to prevent plant injury. For most aphid problems, particularly those associated with leaf curls, insecticides that move systemically within the leaf or plant provide the best control.
Soil-applied systemic insecticides such as imidacloprid and disulfoton will be taken up by the tree's roots and transported to the leaves thereby killing the aphids. Insecticides effect insects not plants so if the hostas, and day lillies have aphids on them they will be benefited by the insecticide control. Other plants will not control the aphids.