Question
Oak tree limb
All of the oak trees in the surrounding area are raining sap when the sun is out. Also the small limbs are covered with bumps that are filled with some type of clear liquid. Some have dried up and are filled with powder now, but the trees have very little leaf growth so far and it is almost July. Some of the smaller trees seam to be dead. Is this a natural cycle in the trees or is it a wide spread disease or insect? It looks like some kind of an insect feeding on the tree to me
Thanks,
Steve Haver
AnswerSounds 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.
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.
Here is a link to more information on this product.
http://www.bayeradvanced.com/product/Tree-Shrub-Insect-Control/concentrate.html
