Question
We planted a Globe Willow in our back yard - west side of the house - about 3 or 4 years ago.  It's really a lovely tree but today we found the bark on the truck and on some of the limbs were black - upon inspection it is covered in tiny little bugs and a lot of lady bugs.  We sprayed it with Diazionon 25% to kill the bugs - what else can we do to save the tree as we really need it for shade.  Thank you.

Answer
The black is called sooty mold. The bugs sound like an insect called an aphids. These insects suck the plant juices from the plant and secrete a substance called honeydew.

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. Occasionally, aphids may actually kill leaves or small shoots. Since aphids may move from one plant to another, they may transmit plant diseases which contaminate the sucking mouthparts.

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



Controlling the aphids will stop the honeydew and the mold will go away with time. The sooty mold does not hurt the tree but makes it look bad. The Diazinon will kill the aphids but it is a contact insecticide and must be sprayed on the insect for control. Sometimes this is difficult to do with large trees and not all foliage and stems are covered. Aphids have the capability to reproduce quickly and the population will expand fairly fast.

The lady bugs are feeding on the aphids. The spray will kill these also.

Since it is difficult to reach the foliage of a larger tree a new product is also recommended. This is called Bayer Advanced Tree and Shrub Insect Control. This product is applied to the soil around the tree and the roots will transport it to the foliage and twigs and when the aphids suck the plant juices they are killed. This product will protect the tree for the season from these insects. Check with your local nursery for this product. Here is a web link to more information on the Bayer insecticide.

http://www.bayeradvanced.com/product/Tree-Shrub-Insect-Control/concentrate.html