Agriview: Tree stress & ants
by Rick Hirsch

Despite all of the water we are dealing with now, the effects of the droughts of 2005- 06 are still being observed on ornamental shade trees in Henderson County. I have received a number of phone calls recently from people who either have lost or are losing oak trees. A majority of these calls originate from the Cedar Creek Lake area. Observations of dead and declining trees indicate that in most cases no single factor, but a combination of factors are involved in the tree deaths. Age and condition of tree, soil environment, root development and cultural practices contribute to poor tree vigor as will applications of weed killers applied around trees. Some of the trees that are being lost appear to already have been in a declining state of vigor to start with. Usually the first symptom noticed by the tree owner is a general browning of leaves from leaf tips and margins inward. This may occur rapidly (2-3 days) on one branch or the entire tree. In a lot of cases the tree is dead in less than a week.

Many of these trees are in the general area of where a new home or other structure has been built within the past 5 years. Heavy equipment has damaged the root system. Digging of water, sewage, electrical, gas or other lines have damaged parts of the root system. Buildings have been built or at least concrete poured over large areas of the tree's drip line. Soil has been removed or added around the tree. All of these items change the tree's environment. Trees are extremely sensitive to the change of their environment.

All of these things create a stress upon a tree. Tree stress results in a couple of diseases - neither of which is controllable - they are only preventable.

Remember that an awful lot of stress is weather related. Just think back at the record hot, cold, dry and wet conditions which have occurred in Henderson County since 1990. All of these record weather conditions can create severe tree stress. The drought of 1996 had a severe impact as well and last year's drought added a tremendous amount of stress as well.

Stress induced tree diseases do not just happen overnight. These diseases may take 6 months or 5 years or longer to kill a tree. "The straw that broke the camel's back" could be a lot of different things for trees already weakened from other causes.

What can you do to keep trees healthy? Proper fertilization, prompt removal of damaged branches, adequate water, control of insect defoliation and leaf diseases, and aeration of soil under drip lines of trees when soil compaction is a problem all help to maintain tree vigor.

Hypoxylon Canker is one fungal disease that is commonly associated with oak trees that are in a high degree of stress. The disease is first evident as a die-back of one or more branches. The foliage of the diseased limbs turn yellow and dies. This dieback continues from branch to branch through the stem until eventually the tree dies. This may require one or more years depending upon the environment and the amount of stress experienced by the tree. Near death or slightly after the death of the tree the outer bark sloughs off, exposing large masses of brown, dusting one celled spores. Within a few weeks these spores are gone and a grayish surface is visible. This is covered with numerous black fruiting structures.

BATTLING HOUSEHOLD ANTS:

Ants are one of the most common household pests you are likely to encounter. They get into trash cans, open food, dog food and other sources of sugar or protein and can be quite a real nuisance around the house.

Probably the most common household ants are the tiny, yellow-to-light reddish Pharaoh ants. These ants have, through time, become well adjusted to living with man and are quite clever in avoiding attempts to exterminate them. They do not form a stationary nest and when anything disturbs them, they move to a new location some distance from the disturbance.

The problem with trying to poison these little pests is that it normally disturbs those which are not killed and they move away from the poison. They are then able to rebuild their populations and in a matter of days, are back causing the same headaches as before.

The solution, then, is to poison them without their realizing they are being poisoned (or without disturbing them). Here is one suggested method: mix one teaspoon of boric acid crystals in 1-2 ounces of hot water. Heat and stir until the boric acid dissolves, then mix the solution with one cup Karo corn syrup. Put this bait out in small amounts at many bait stations. Plastic pill or metal bottle caps will work well to hold the bait. Place baits in and around those areas of the house where ants have been seen. Be sure to keep baits moist by replacing them or adding a drop or two of water every 3-4 days. Boric acid crystals can be bought at most drug stores and many supermarkets. The material is safe to use, but as with all chemical insect control, it should be used with caution and kept out of the reach of children. This method of controlling Pharoah ants is simple and inexpensive, but it does take time. You should not expect complete control for a period of several weeks.

(Rick Hirsch is the Henderson County Extension Agent - Agriculture for Texas Cooperative Extension. Visit web page http:// henderson-co.tamu.edu.)