Question
I have two 20 year old little leaf lindens that have been dropping honeydew the last few years. One of them overhangs our parking area and makes a mess of our cars. I recently put the Bayer insect product around the base of the tree, but that may take weeks to work. I have sprayed the trees with a hose-end sprayer of "Eight" insect control, but could not reach the entire tree-maybe three quarters of the tree. Still I have honeydew dropping. I don't know what type of insect is causing this, maybe aphids or scales? The leaves on the tree by the driveway are covered in holes. My family wants to cut the trees down but I hope I can find a fix for the honeydew drop. Any suggestions? thanks for your help.
Sue

Answer
Sound like aphids or scale insects. Both will suck the plant juices from the leaves and twigs and secrete a substance called honeydews. Honeydew is high in sugar content and is sticky to the touch. Usually a black sooty mild will grow on the honeydew making everything black and sticky.

You can either spray the tree's foliage or use a systemic insecticide on the soil beneath and the tree will absorb the insecticide through the roots and take the insecticide to the leaves and twigs. Spraying a large tree can be difficult.


Chemical Control - Contact Insecticides 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),  bifenthrin (Talstar), chlorpyrifos (Dursban),  diazinon,  malathion, nicotine sulfate, pyrethrum, rotenone, resmethrin, and tetramethrin + sumithrin.

Chemical Control - Systemic Insecticides 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. Systemic insecticides include: acephate (Orthene)


Certain persistent insecticides that move systemically in the plant may provide control through the fall. 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.  

Since you have tried the spray I would use the bayer product. it will take a week or so to take effect but it has a linger last effect. Here is a web link to this product. http://www.bayeradvanced.com/product/Tree-Shrub-Insect-Control/concentrate.html
Check with your local nursery for the product.