Railroad Ties and Timbers

With the retrenchment of railroads and the abandonment of many miles of railroad lines, there is an abundance of used railroad ties and timbers that are being sold by garden stores as cheap materials for landscaping. Thus, in some hilly areas of the Pacific Northwest and elsewhere in the United States, these used railroad ties are used to tier yards, to border flower gardens, and for other landscaping purposes. These ties have been treated with creosote, and most people think they are protected from wood-boring insect infestations. However, not only is this incorrect, but railroad ties are one of the major sources of colonies of carpenter ants infesting structures.

Carpenter ants held in containers in the laboratory with creosote-treated chips from old railroad ties were unaffected. Additionally, when the ties weather and crack open, the penetration of the creosote is only about ½ inch deep. Carpenter ants enter through these cracks and excavate the wood in the interior.

Since the ties are always partially buried in a watered lawn or garden, moisture conditions are usually ideal for carpenter ants. Many areas in the state of Washington are recognized as nearly untreatable for carpenter ant infestations unless the ties are removed. The ants in the adjacent houses can be temporarily controlled with insecticides, but the ants in parent colonies that are in the ties simply establish new satellite colonies in other structures, or even return to the original structure once the effects of the residual insecticide abate.

Unfortunately, treatment of railroad tie and timber landscaping is often difficult if not nearly impossible. Retaining walls and landscaping timbers often abut the house with no space between them. They are also sometimes completely buried, or in the case of retaining walls, have soil on one entire side of the wall. Carpenter ants will tunnel behind the ties through the soil so they are very difficult to treat.

Cement or brick patios and sidewalks also provide access from landscaping timbers to houses, as the ants simply tunnel under them into the house. An additional consideration is that soil tends to bind to most insecticides quickly, so they are not available to kill the ants.

Examples of these types of situations are numerous, but we have picked three typical ones to illustrate our point.

EXAMPLE 1. We received a strident telephone call from a music professor whose office and laboratory were in an older campus building. Carpenter ants had invaded the building in force, and had devastated the professor's handmade piano keys, which were stored in a drawer. We dumped the contents of the drawer, and several hundred ants scurried away.

University maintenance personnel then asked us to treat the ants. The ants were found under the floor of the old building, in a retaining wall, and in a hollow tree about 170 feet away. We agreed to treat the ants, but only under three conditions:

• As the floor was replaced, as part of routine maintenance and repair, we would have to be permitted to treat the subfloor with a dust before the new floor was laid.

• A 4-foot-tall, 12 × 12 inch creosote retaining wall that was adjacent to the building would have to be removed.

• Maintenance personnel would have to furnish us with a hydraulic lift bucket so a large infested tree nearby could be drilled and treated from a height of 10 feet.

All conditions were agreed to, and when the work started on the retaining wall, it was soon discovered that not only was this the site of the parent colony as suspected, but we were even able to collect the physogastric(abdomen greatly enlarged for egg laying) queen. The partly hollow tree contained an enormous satellite colony. Control was effected quickly, and no further problems have emerged.

EXAMPLE 2. The second example concerned a relatively new home with about 800 feet of railroad tie retaining walls in the back yard. We agreed to treat the house by using a power duster to inject the wall voids, supplemented by a perimeter spray of a synthetic pyrethroid using about 3 gallons of material. We did not treat the retaining walls. We cautioned the homeowner that problems would continue, and pointed out two areas in the retaining wall that we thought contained colonies. We were assured that some of the walls would be removed.

Several weeks later, we received an excited phone call. "We are removing the wall where you indicated, and ants are going everywhere. What should we do?" We asked them to vacuum and freeze the ants, which they did.

Two weeks later, the same scene was repeated as the second indicated wall was removed. With these removals and spraying of the area with a pyrethroid insecti cide, no additional ants have been seen. The remainder of the wall is still slated for removal as soon as financially possible.

EXAMPLE 3. The third example was a true horror story. The retaining walls in the back yard of a home consisted of 1,150 feet of 1-to-3-foot-high retaining wall. It was financially impossible to remove the walls. We agreed to treat the house with dust and a perimeter spray, but in addition we drilled into the soil at 10-inch intervals behind all the walls with a ¾ inch × 3 foot bit, and drenched the holes with insecticide. Additionally, the retaining walls were sprayed with synthetic pyrethroid. In all, over 850 gallons of insecticide were used just to treat the walls.

There have been no ants present since our treatment, and the homeowners are advising all who will listen against the use of creosote timbers as a retaining wall material. In a normal situation, no homeowner could afford all the work and insecticide we used to treat this home.

The solution to this problem seems simple the manufacture and sale of 8foot lengths of hollow, cement "railroad ties." The ties should be made square, with two holes per length so a number of ties can be stacked and pinned in place with fiberglass rods.

Cement is an extremely adaptable material, and the ties could be made in any color and in various designs (e.g. simulated wood grain). The ties, cast as hollow lengths, would be lighter than used railroad ties, and would ensure that decay fungi and wood-destroying insects would never be a problem.

Pest control operators who also hold a contractor's license for removing honeybee colonies from houses and repairing the damage might consider replacing the wood ties themselves as part of the treatment. Other PCOs could team together with a landscaping company (possibly for a referral fee) to treat the old infested wood as it is removed for replacement with cement ties.