I have a large tulip tree; the roots of this tree were damaged during a fence installation. Subsequently the tree developed slime flux and many branches died. I have kept the tree well-watered and fertilized, and it appears to be recovering and making much new growth. When would be the proper time to remove the dead branches from the tree? They are unsightly and some are quite large and could damage structures if they fell.

The tulip tree (Liriodendron tulipifera) is not a tree for residential property. Many times we as gardeners just cannot help ourselves and purchase or inherit a tree that struggles where it is planted. The tulip tree needs a large, open area to grow and develop its branches and root system to display its real beauty and remain healthy.

You are taking the correct steps to insure the health and longevity of your tree after its injury. Since there are no curative or preventive measures for slime flux, you are correct in practicing IPM (Integrated Pest Management) to maintain the tree in a state of vigor by using a consistent watering and fertilization program and minimizing future wounds or injuries.

The best time to prune off the dead limbs would be in the tree’s dormant season, leaving less chance to spread the disease. When pruning, use a 20 percent bleach solution in water to dip and wipe your tools when changing cutting areas. This procedure will stop the spread of the disease from infected tools to healthy tree tissue.

Lastly, please investigate all the symptoms of slime flux to confirm your diagnosis, as this bacterial disease does not usually affect tulip trees in our area. Other diseases and insects are more likely to cause a problem showing some of the same symptoms, like aphids, which secrete large quantities of “honeydew” (a clear sticky substance). Unlike slime flux, however, there is a treatment program for aphids.

What is killing the hop hornbeam trees? I have lost mature trees and there are several more that are dying. I have also seen sick trees along 7 Mile in Northville and at Ford Field in Northville. Can this be related to the emerald ash borer?

Hop hornbeams are in the birch tree family. The pattern of destruction is very similar to the emerald ash borer’s (EAB) attack on ash trees. Unfortunately it appears the bronze birch borer has infested and is decimating the hornbeams. Not only are birch borers very similar in size and shape, but their life cycle pattern mimics the notorious EAB. However, birch borers are native to North America, occurring throughout Canada and the U.S. to as far south as Maryland to Utah. They are not an alien introduction.

The first symptom of infestation is the dieback in the upper crown. This progresses to twig and branch dieback. Trees may take several years before dying, although they may die during a single year if conditions are optimum. The tree’s decline may be reversed in the early stages but not likely if more than 50 percent of the crown is damaged. The birch borer also mines extensive tunnels through the inner tree tissue like the EAB. When the weather cools, as is typical in a Michigan autumn, the larvae stop feeding and overwinter in the tree. Because of prolonged adult emergence and the long egg-laying period of this insect, all larval stages can be present during winter, from newly hatched to fully grown.

To reduce the number of adult borers, recently killed or heavily infested trees should be cut down and destroyed. This limits the adults emerging in spring. Prune out dead and dying branches slightly below the point of dead wood. Insecticides can be applied to the surface of the tree bark to kill larvae emerging from eggs. Sometimes as many as three applications are required from mid-May to mid-July to handle the repeated hatchings from the staggered egg laying. Vigilance, control, and integrated pest management are the only real tools against this destructive insect.