Aug 31,2007 00:00
Q: When the cicadas arrived in June, the two sugar maples in my front yard were inundated with them. Once they were gone, small branches with a few leaves on them began falling. They are numerous and continue to fall. I see no end in sight, and the tree is starting to look sparse.
A: This sounds like typical cicada damage. The cicada pruned the tree branches for you, even though the trees probably didn't need pruning.
Take a close look at the remaining branches to prune any stubs back to a live bud or branch. Remove any dead twigs still hanging if you want to, and do any additional pruning to retain a pretty shape. Keep the trees watered in dry conditions and do a fall fertilizing after the leaves have fallen off. Fortunately, it is unlikely that there is any permanent damage.
Q: I need help with one of my Japanese willows, which is about 10 years old and has a trunk about 10 inches across. About four weeks ago it developed a small pea-sized hole about 5 feet from the ground that began to ooze a smelly white substance that looks like shaving cream. It has continued to bleed. Since it smells so bad, I wash it from the trunk every day.
I looked for cracks in the tree trunk, but there aren't any. Then I thought perhaps it's an insect that bored a hole. But the discharge is continuous and I worry that the tree is going to die from this. I noticed that the leaves are a lighter shade of green than the six other Niobe willows I have. I water it often and give it a liquid plant food once a week.
I would be grateful for your advice. I am not sure what to do.
A: There are three possible causes for the oozing white sap. Boring insects create holes ranging from about pinhead size to larger than a pencil eraser in diameter. Some are round and some are flat on one side like a capital D. The insect will create a byproduct of cellulose and droppings called frass. It looks like sawdust or moist sawdust. Sometimes it is found stuffing the tunnel as the insect moves through the trunk, or it is pushed out of the hole and accumulates in piles at the base of the plant.
The natural reaction of the plant is to produce extra sap in an attempt to drown the insect. Some of the sap will be liquid and run down the side of the trunk. In some plants, such as evergreens and pin cherries, the sap will accumulate around the hole in large sticky balls.
If the insect is still alive and eating, you may be able to run a wire into the hole to see how far it goes and to kill it. Many borers have convoluted tunnels, however, so that may be hard to do. Try washing out the hole to see how far it goes.
Woodpeckers tend to create larger visible areas of bark damage around the hole as they widen it out to get to the insect they are after. If there is an insect in the trunk, it is a good thing to have the woodpecker trying to get it out for you. The tree may still react to the damage with a large flow of sap, but it should heal in a few days.
Bacteria can grow on the sap and cellulose inside a tree trunk. The bacteria and fungi that decay wood may get into live trees through insect and animal damage, through cracks created during wind storms and through holes left from dead branches that die naturally on all plants.
Since there is very little oxygen inside a tree trunk, the bacteria grow anaerobically. The result is bad-smelling sap oozing out of the tree due to the pressure that builds up from the created gasses. The sap is often colored white or yellow because of the bacteria. It is kind of like a runny nose in appearance. The colored sap stains the bark, making it obvious the tree has a problem. It is easy to spot elm trees that commonly have this problem because two branches split and the dead bark between the trunks starts to decay.
Boring insect females pick trees that are already weak to lay their eggs since the weak tree has less sap to use in its attempt to kill the larvae. Your tree is notably weaker because the leaves are a lighter shade of green than the other trees. You should keep up the watering and fertilizing, but stop fertilizing four to six weeks ahead of the first frost date in order for the tree to go dormant properly. You might want to try a systemic insecticide if you find borers present.
If the tree can maintain its health, it will compartmentalize that area of the tree trunk from the rest of the tree and it should heal on its own. Willows are all more prone to insects, diseases and shorter life spans than most other trees.
E-mail questions to Jeff Rugg at firstname.lastname@example.org.© Copley News Service