Question
QUESTION: I live outside Placerville, CA.  We have many cedar trees, (10 or so), and some of the needles are turning brown.  My concern is that for about 2 months now, they all are dropping LOTS of gold colored sap droplets.  The droplets are approximately 1/8"-1/4", and are thick all over the ground around the tree.  Everyday there is lots more droplets of sap.  It has become a problem because it drops on my car, the dog tracks it in the house, but worst of all I fear the trees are dying.  Is this a root rot?  Is it bark beetles?  Do you think the trees should be taken out?

ANSWER: Sounds like an insect called aphids.


Aphids are small (1/16-1/8 inch long), soft bodied insects commonly called plant lice or ant cows. Virtually every plant has at least one aphid species that attacks it. These small insects are masters of reproduction and are often found in great numbers on stems or leaves. Some species even feed on the roots of plants. They range in color from green to brown, red, black or purple. Some species may even have different color forms in the same colony. Most have the soft exoskeleton exposed, but some species produce waxy, cottony strands which cover the body. These are often called woolly aphids.

Aphids are identified by their sucking mouthparts, long, thin legs, long antennae, pear-shaped body and pair of tube-like structures (called cornicles) arising from the posterior of the abdomen. A hand lens may be needed to see the short cornicles of some species. These cornicles apparently are the ducts of glands that produce alarm odors. Aphids may be winged or wingless and colonies often have both forms.

Aphids excrete a sugary liquid called honeydew. This honeydew drips onto plant foliage or other structures and provides a suitable place for black sooty molds to grow. Ants often tend or care for aphids in return for the honeydew. Therefore, if ants are running over a plant, look carefully for aphids.

Each plant reacts differently to aphid attacks. Some plants show no response to the aphids, while other plants produce distorted (twisted, curled or swollen) leaves or stems.

Probably the most common disturbance caused by aphids is their never-ending production of honeydew. This sweet liquid drips onto plant foliage and stems and is soon covered with black sooty mold. Cars, sidewalks, and lawn furniture under trees with aphids are also covered with this sticky fluid. Ants, flies and wasps appreciate the sugary meal and can become a nuisance of their own. Even though plants may look bad from the growth of sooty molds, these fungi do not damage the plant tissues. Once the aphids disappear, the sooty mold often dries up and falls off the plant.

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
These above will need to be sprayed on the foliage and branches for control. This is sometimes hard on large trees. 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  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.
I would recommend that you use the Bayer Advanced this spring. The roots will take the insecticide to the foliage and kill  the aphids when they suck the plant juices. This should last all season.

Check with your local nursery for these insecticides.


---------- FOLLOW-UP ----------

QUESTION: I will consider your suggestions for insecticide next spring.  But from what I hear we are going into a heavy winter.  Do you feel this will effect the integrity of the trees?  We live in an area that does get snow and high winds-is there something we can do now? In your opinion, would these trees be more likely to fall?

Answer
The problem with winter and breakage is ice forming on the foliage. Snow usually will nor break the foliage. The other problem can be sun scald.
During the fall an evergreen tree prepares for winter by going through a process called hardening off. The tree shuts down its growth mechanisms and slows down its rate of transpiration and consumption of nutrients. This process is obvious in deciduous trees as they lose their leaves in the fall. This is less obvious with evergreen trees and shrubs as they retain their leaves throughout the winter. But rest assured the evergreen trees in this region do go through the hardening off process. Winter damage occurs on trees and shrubs such as cedar, during days when the sun provides continuous heat throughout the day. The cells of the foliage of the plant thaw out during the day, even if the air temperature is below freezing. When night comes and the temperature falls, the cells refreeze. This causes the cells in the leaves to burst and eventually die off. This creates the dead foliage you see in the spring. This process can be magnified if the sun reflects off of the snow or the windows of your house, creating an intensified heat, accelerating the death of the foliage. Wind can also cause damage to plants like these as well. The continuous drying cold winds of winter can evaporate any moisture the tree has preserved for the winter months, from its leaves. Over time the foliage will dry out and wither also causing areas of brown and dead foliage.
In winter seasons, when the snow is deep this damage often occurs above the snow line. In winters with little snow, the damage can occur over the full length of the shrub. Trees and shrubs bought at out local nurseries are winter hardy for this area, but we cannot always predict what the winter season may bring. Sometimes we need to assist our shrubs and trees in order for them to maintain their aesthetic quality. To prevent sunburn in future winters I recommend constructing a barrier around the susceptible sides of the tree. You need not wrap it tightly in burlap just create a sun screen by constructing a burlap fence around the shrub. For a cedar hedge you will have to run your burlap fence the length of the hedge on the side that sustains damage. If you have trouble constructing a protection screen then you could wrap the entire tree/shrub. Small evergreen shrubs such a juniper, yew and cedar can be mounded completely with snow throughout the winter. If you are unsure of the amount of snow you will have available in your yard, a coverage of loose leaves will offer protection.
In order to correct the damage from last season you can trim out the dead leaves from the cedar, if the damage is not too extensive. Do not completely trim the damage out if it will create bald spots, or make the shape of the tree lopsided. If this is the case leave the damaged foliage on the trees and see if time will allow for new foliage to develop and replace the damaged foliage. If the evergreen damaged is a juniper or yew, for instance, you can prune the branches as needed to remove the damage. Once you have the tree cleaned up ( June to mid-July is the best time for evergreen trimming) you can apply a fertilizer to the ground around the tree or shrub. Purchase a good quality fertilizer for evergreen trees (this is a fertilizer with a higher nitrogen content). Follow the instructions carefully and reapply throughout the growing seasons as per the recommendations on your fertilizer product. As with your perennial garden, you would prepare the trees and shrubs for winter by making sure the ground is very moist. If the fall season is dry, you may have to water your trees and shrubs with your hose to ensure the ground is saturated with moisture prior to freeze up. By doing this you will ensure that the roots are embedded in the frozen ground for the entire winter and will prevent frost heaving. It is also important that the roots stay frozen completely throughout he winter to prevent damage to the roots from continuous thawing and freezing.
Following these tips will help to ensure that your cedars and other evergreens will look their best summer and winter for many years to come.