A Greener View: Sparing a tree infected by carpenter ants
Jun 22,2007 00:00 by Jeff_Rugg

Q: I thought someone had piled some sand against the base of one of my trees, but it turned out to be sawdust from some large black ants.

Are they hollowing out my tree? Do I need to cut it down or how else do I get rid of the ants?

A: Carpenter ants are commonly found in trees and in buildings, so it is advisable that you treat the tree and check to see if they have invaded your house. Satellite colonies can be found in firewood piles, logs and even in just a dead tree limb. They can travel over 100 feet from a tree to a structure, so other houses and garages may need inspections.

They are not especially harmful to most trees. They merely remove the existing soft rotting wood, which is the sawdust you discovered. Something else damaged the tree and decay is breaking down the cellulose.

Once in the tree, the colony is protected and difficult to treat. Apply a powdered or dust version of an insecticide (that mentions carpenter ants on the label) into as much of the tree cavity as possible and around the base of the tree.

It may be necessary to also apply the insecticide around the base of your home. If they are in a building with a food source, they don't have to leave. If there is a queen, the colony will grow indoors.

Don't try to plug the hole in the tree or apply tree paints of any kind. These materials will just seal in the microorganisms and promote more decay. It is possible that the tree needs to be removed because of the decay hollowing it out, but probably not due to the ants. A licensed arborist will be better able to diagnose the potential hazard the tree presents.

Q: I have treated my peach and apple trees for several years with a combination spray that has both a fungicide and an insecticide. This year there appears to be almost no fruit set on the trees. I fertilize and prune the trees properly and was wondering what suggestions you might have.

A: I don't recommend using a combination spray because often you don't have both problems at once. Spraying a fungicide during the time the trees are in bloom is beneficial to prevent brown rot, a disease common in peaches, cherries and apricots. If you sprayed during the midday hours, you may have drastically reduced your bee population, which is necessary for pollination in those crops. All insecticides used on food crops should be sprayed in the early morning and late evening when the bees are less active.

Spraying an insecticide on those trees later in the season to prevent worms entering the fruits is done at a time when the fungicide is unnecessary; it is essentially an application of a pollution that has no benefit to the crop.

Try getting separate sprays for each problem as it arises. It may be that in past years you sprayed during a time that the bees were not around in large numbers, therefore not reducing the fruit set.

Another possible answer to your low fruit set problem is that some fruit and ornamental trees go into an every other year fruiting cycle. The tree needs to store up a large amount of carbohydrates to be able to develop flower buds in the fall and bloom the following spring.

During a summer with a large amount of fruit growing, the tree uses the carbohydrates to produce the fruit and less is left for flower bud production. Many people like to see huge crops from their fruit trees, except for nurserymen. An overabundance in one year will probably be hard to pick and some will go to waste, leaving little fruit to be picked the following year.

The solution is to reduce the amount of fruit during the years where the tree tries to over-produce. While the fruits are small, thin out as much as half the fruit on the tree. The remaining fruit will be healthier and grow to a larger size. The tree will take the extra carbohydrates and then use them to produce more flower buds for the following spring.

For some trees like oaks, the whole forest will get into one of these cycles of producing heavily in one year and poorly for several years later.

Another probable cause is lack of carbohydrate production due to poor growing conditions. Many areas have experienced local droughts that have serious impact on tree health. A tree that with past good health may have enough carbohydrates stored in the trunk to survive drought, construction damage or insect and disease problems that occur in one or even two years; however, the tree's health declines visibly. Extra watering and possibly more fertilization may be necessary to bring the tree back to good health.

E-mail questions to Jeff Rugg at info@greenerview.com.

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