Question
We live in Riverbank California, in the San Joaquin Valley. We have a raywood ash that is 18 years old.  It overhangs a wood deck and concrete pavers the deck(s) are always covered with sticky sap.  Examination doesn't reveal any aphids or signs of borers but all the leaves appear to have drips of sap on them.  Is there another pest that could be causing the "drip"?  Is there some treatment that would help as a broad spectrum cureall?

The tree appears healthy with lush vigorous growth.  Colors in October and loses it's leaves in late November or early December.
It normally flowers in late January or early February. One year we had shot holes in the leaves.....but that isn't happening now.
The sap problem has been going on for a lot of years requiring frequent washing of the wood deck and concrete pavers.
Any suggestions would be welcome.

Mary Lou Rice

Answer
Sounds like the problem is a scale insect. Scale insects are so prolific that they quite often cover twigs and branches. The insect lives under the shell like structure and sucks the plant juices from the twig. And secrete a substance called honeydew which is high in sugar content and sticky. A sooty mold may also grow on the honeydew.
Large numbers of these soft scales may give an infested twig a warty appearance. One of the first indications of an infestation of this pest is the abundance of honeydew (sticky, sugar-rich material) secreted by developing soft scales during the growing season. Ant and wasp populations that seek the honeydew are often found in association with this soft scale insect. These ants may need to be managed since they protect this scale insect from predators and parasitoids. The honeydew is a substrate on which black sooty mold grows. The sooty mold may turn the leaves, twigs, and other surfaces beneath an infestation black. Feeding by this pest may weaken young trees by removing plant fluid. Bees and ants feed on the honeydew.

The scales are difficult to control after the insect has constructed the scale. Systemic insecticides are absorbed and moved within plants. If the plant is infested with a scale species susceptible to systemic insecticide, systemics are particularly useful where it is not practical to spray because plants are large or spray may drift to unintended areas. Depending on the product, systemic insecticide may be applied by spraying foliage, or applying on or into soil beneath trees and shrubs, where the insecticide is absorbed by roots.

There are some newer insecticides that will control the scales that are applied to the soil and the roots transport the insecticide to the branches and leaves and when the scale sucks the juices it kills the insect. Certain persistent insecticides that move systemically in the plant may provide control through the fall. Imidacloprid (Bayer Advanced  Tree and Shrub Insect Control) is a newly available systemic insecticide that can provide scale and aphid control on trees for several months following application to the soil.  


I would use the Bayer Advanmaced Tree and Shrub Insect Control. Apply to the soil around the tree and the roots will carry it to the twigs and leaves and when the scale insects suck the plant juices they are killed. It may take a couple of weeks for the insecticide too reach the top of larger tree. But it is easier than the spray. Here is a web link  to this product. check with your local garden type store for this. http://www.bayeradvanced.com/tree-shrub-care/products/12-month-tree-shrub-insect...