Gulf Construction Online - Masa slams the door on pests

Chemicals in Construction

Masa slams the door on pests

With termite infestations being a major concern with property developers in the region, Masa Establishment for Pest Management Services outlines the pros and cons of the various control practices that are in vogue.

01 September 2005

Subterranean termites are a severe problem in structures worldwide and property developers and homeowners need to consider the benefits of prevention of termite attacks as opposed to the risks likely associated with remedial control.

Soil insecticide applications represent the most widely accepted method of creating a barrier to termite infestation. Even under the desert environmental conditions, where heat promote insecticidal degradation, the cyclodine soil insecticides such as chlordane and aldrin, could provide 25 years of structural protection. However, these materials are no longer available for the use by pest control industry in most part of the world, and their replacements require more frequent reapplications.
Other alternative methods for termite control have gained importance as a result of the discontinuance of most of the long lasting cyclodine soil insecticides and increasing environmental awareness over possible ill effects from the application of large quantities of liquid insecticide for termite control. But soil insecticide application is still remained as the most effective control methods due to several operational functional properties.

Chemical barriers
For chemical barriers to be effective, there has to be a continuous and uninterrupted layer of the chemical beneath the entire structure. Which means that all foundations should be surrounded by, and in contact with an insecticide treated layer of soil.
The preparation of chemical barriers after completing all site works – leveling, excavation, filling and compaction; and after the installation of ground located electrical conduits and plumbing pipes – is a sure mode to check termite infestations. This could be done immediately before laying the floors – in buildings with suspended floors – or before placement of waterproofing membranes – for buildings with concrete floors.
Correct installation of a chemical termite barrier involves at least two separate treatments. Following the formation of the major barrier under the concrete slab, final treatment has to be made to the outer perimeter of the foundations after all service connections have been completed and all the backfill is in place. An initial treatment to the foundations is also required where these are poured separate to the concrete slab.

Barriers for existing buildings
Where the sub-floor area cannot be reached, a trench extending down to the top of the foundation and 150 mm wide around and outside of the building is an option. Dig the trench in contact with the foundations and then backfill it with treated soil using 100 litre /cu m of insecticide emulsion.
Another application method for external barriers is to pump insecticide emulsion through a specially designed perforated pipe. The pipe is driven into the ground around the perimeter of the building, close to the foundations, to a depth of 300 mm at frequent intervals so that insecticides from adjacent injections meet. Care should be taken to avoid planting trees close to the treated buildings as their roots can breach through the insecticide barriers.

Chemical baits
Wood or cellulose favoured by termites can be impregnated with a toxicant and/or insect growth regulator (IGR). Termite workers feed in the treated substance and carry it back to the nest, reducing or eliminating the entire colony. Termites normally grow by molting (shedding their exoskeleton). The bait hexaflumuron is a "chitin synthesis inhibitor" that prevents termites from growing by stopping the molting process. As a result, the colony is eliminated over time.
Soil-applied termiticide as a termite bait to control subterranean termite is one of the latest techniques. Although baiting for termite is not a new idea, this technology, which is relatively new, has been commercialised and number of bait products and baiting systems are available.
The number and placement of the bait stations vary depending on the product used the characteristics of the site and the amount of termite activity. A station generally contains a cellulose-based material impregnated with an insect growth regulator or a slow acting toxicant. The bait is usually placed inside a child resistant housing. Other baiting strategies include interceptive baiting, in which aboveground bait systems are placed in the path of the termites (in mud tubes or areas of wood damage and termites presence), so that the termites come in direct contact with the bait. Examples of active ingredients included in termite baits are hexaflumuron (IGR), sulfluramid, hydramethylnon, avermetin and Metarhizium anisopliae (a fungus).
As with any technology, there are advantages and disadvantages to the use of termite baits compared to the use of liquid termiticides. One advantage is ease of use as the drilling of structural concrete is not required and the toxicant is distributed from a point source.
The active ingredients in baits are generally less toxic than those in soil insecticides, which add to their environmental friendliness. There are several disadvantages to termite baits. Bait programmes are usually more expensive and may require continuous monitoring after colony elimination or suppression has been attained. The major disadvantage is the length of times it takes a bait to eliminate the colony.
While baits are another useful, innovative tool for termite control, they should be viewed as an addition to existing termite control methods and not necessarily a replacement for them.

Biotermiticides
Biotermiticides, such as fungi, nematodes, bacteria and so forth, still need further research and development to maximise their potential. A fungus metarhizium anisopliae can be used by injecting the product into galleries, infested walls, and other moist areas where the humidity accelerates the fungal growth. Nematodes are applied to the soil or directly into mud tubes. The fungus metarhizium anisopliae is a biological termiticide, which is odorless, vaporless, non-staining and infected termites can pass the agent (fungus) to other termites through the horizontal transfer effect.

Use of borates
The use of borates (disodium octaborate tetrahydrate, in several formulations, to penetrate wood for the local control of termites has shown potential in preventing infestations. Results in eliminating existing infestations have been variable; thus the use of borates for controlling established infestations must be evaluated on a case-by case basis.

Foam formulations
Formulations of soil-applied termiticides are a means of delivering termiticide to areas difficult to reach with liquid formulations. Foams penetrate hard-to-reach cavities and voids and they improve termiticide distribution in soils. The most difficult area to achieve uniform and continuous insecticide distribution is under slabs, where it is difficult to see the actual deposition of the termiticide.
The liquid termiticide in the foam is combined with air to create uniform, small diameter bubbles. The foam carries the liquid termiticide in the spaces between the bubbles. The fact that foam is less dense than liquid enables it to dispense uniformly. The foaming agent delays collapse of the bubbles, providing more time for the insecticide to reach the desired areas. Surfactants in the foam also improve chemical penetration.
Foam treatments do not replace other soil applications – they supplement these applications, so that the gaps left by conventional treatments can be successfully treated.
Altis and Termguard are under-slab reticulation systems currently approved for use. They are installed pre-construction, underneath the slab and waterproof membrane. A chemical barrier is installed by injecting the insecticide under slab at any convenient time between pouring the slab and completion of the house. If a reticulation system is installed, it must be charged with chemical soon after the house is completed to satisfy building requirements.
Termiticide barriers around the outer perimeter of a building are not considered a significant health risk. This is partly due to the binding of the chemical to the soil and the evaporation of the solvents and emulsifiers soon after application. It is possible to dispense with this treatment if the outer edge of the concrete slab is exposed 70 mm above the final finish level of the soil.
But in the control and prevention of termite infestations, the application of termiticide to soil still supersedes all the above alternative methods. At present, this method is the ultimate measure in termite control and prevention. It involves the judicial application of chemicals labelled as termiticides. Although it has several drawbacks from the environmental point of view, application of insecticide to soil make a termite barrier is the most effective, and easy to use method. Unlike other methods it gives direct results in a shorter time period and is long lasting.
Masa Establishment for Pest Extermination Services is a pest management, research and consulting firm dedicated to researching and developing effective alternatives to conventional pest control methods and making this knowledge available to you as our prospective and valued client. Through its research and development division, the company continues to uncover new and very old ways of controlling unwanted pests without the abuse of pesticides in homes or offices.
These alternative methods range from modifying cultural behavior to minimal use of least toxic chemicals or completely non-chemical, natural solutions. These methods require a greater understanding of our complex ecosystem, which makes the educational process as important as correct application.