Question
Hi Jim,

We are Americans living in  Southern Greece.  About 12 years ago we brought a pecan in the shell over here and planted it.  It is now a very large tree in my driveway.  The tree offers wonderful shade for our vehicles but every year during the summer months it produces a sticky substance that covers all the vehicles parked under it.  Could you enlighten me as to what this could be?

Answer
Pecans are easily attacked by an insect called aphids. These soft bodied insects suck the plant juices from the leaves and excrete a substance called honeydew. Honeydew is very high in sugar content whch makes the sticky feeling. Control the aphids and the honeydew will stop. You will have to spray all the foliage and this maybe a problem with tall trees.  Numerous contact insecticides are registered for aphid control. Since aphids are often placed under considerable pesticide pressure in field crops and greenhouses, they may be resistant to certain categories of insecticides. Therefore, if you do not obtain reasonable control, consider rotation to another insecticide. Contact insecticides currently registered for aphid control include: acephate (Orthene), bendiocarb (Ficam, Turcam)(*), bifenthrin (Talstar), chlorpyrifos (Dursban), cyfluthrin (Tempo)(*), diazinon, endosulfan (Thiodan) (*), fenitrothion (Pestroy)(*), fluvalinate (Mavrik)(*), lindane, malathion, nicotine sulfate, pyrethrum, permethrin (*), rotenone, resmethrin, and tetramethrin + sumithrin.

Several systemic insecticides are useful in aphid control. Aphids have sucking mouthparts and are thus very susceptible to pesticides located in the plant vascular system. Some of the systemic insecticides also have contact activity. Systemics injected or applied to the ground are less harmful to beneficial insects.  Imidacloprid (Bayer Advanced Garden Tree and Shrub Insect Control) is a newly available systemic insecticide that can provide aphid control on trees for several months following application to the soil. Check with your local nursery for this systemic insecticide.