DR NATALIO MERCADO, company entomologist at Masa Establishment’s Research and Development Department, outlines the procedures that should be followed for treating soil.

01 September 2011

IN recent years, the treatment of buildings under construction to prevent pest infestation has become a standard procedure in Saudi Arabia, for slab, on the ground and basement construction.

Among the main methods used in termite-proofing and control is soil treatment.  However, the widely varying types of construction makes it vital that the termite control specialist gives careful consideration to the principles of control involved in each situation and adopts methods that fit the situation, whether soil treatment, installation of baits or physical barriers such as metal screens.

The specialist’s major objective in treating soil for subterranean termites is to establish a chemical barrier between the termite nest, usually in the ground, and the wood in a structure. In buildings under construction, this is accomplished by keeping wood out of contact with the ground and by pre-treating the soil below the foundation with insecticide to establish a chemical barrier.

Termiticide used in pretreatment must be applied to the soil with such thoroughness and uniformity that it provides a barrier by “lateral soil movement” to all routes of termite entry, which can persist unchanged in the soil for years in bound residue of recalcitrants (which cannot be extracted from soil except with running water).

However, pretreatment should be carried out only when favourable conditions prevail. Wet soil should not be treated because there is likely to be considerable a surface flow of termiticide from the site of application. If the treated area is not covered immediately by concrete, precautions must be taken using plastic sheets to prevent contact or disturbance of the treatment by people and/animals.

In brick-veneer walls, termites can be controlled using termiticides alone in most situations. One technique used is to remove the soil adjacent to the foundation to within about one foot above the footing in a process of trenching. As the soil is replaced, it should be treated with termiticide at the rate of four gallons per 10 linear feet for each foot of depth from grade level to footing. The termiticide can also be carried to the level of the footing by injecting it through a long pipe inserted at one foot interval in the process of rodding.

It should be noted, however, that all compounds applied to the soil undergo some form of degradation or breakdown of substances - usually through microbial processes, but also through chemical processes.

Pesticides in the soil are lost through washing, leaching, hydrolysis, volatilisation, photo-degradation, evaporation, and transformation, and other routes.  Hence, it should also be noted that the pesticides may not only lose their original composition but may acquire altogether different forms, sometimes different to the parental compounds.

A key property of pesticides is their persistence – that is, their ability to retain their chemical identity and biological effectiveness for longer periods – which is considered highly desirable for continued control, although it also causes environmental problems; the longer the persistence, the greater the effectiveness – which translates to reduced frequencies of application and cost of management – making persistent pesticides the obvious choice for the pesticide user.

Masa always depends on Imidacloprid 30.5 per cent SC, a suspension concentrate formulation for termite-proofing, prevention, and control. This is a new-generation termiticide with a lethal action on termites. It is odourless and has low mammalian toxicity, has contact and systemic action and impairs the physiological activity of termites; and spreads in all directions by a process called “lateral soil movement” unlike other termiticides that require consistent and uniform application.

The chemical also ensures soil coverage with no gaps and bound residues of recalcitrants (non-detectable treated zones for termites) that function not as repellent zones but as “killing fields” whose effects may be transmissible to other termites and leads to contamination of the colony.

Imidacloprid stays for many years following the initial treatment, depending on application, climatic conditions, soil composition, moisture level, building type and secondary infestation caused by bringing termite-contaminated products in the premises.

The uniqueness of this chemical is that it is a water-based product and has no solvents, which prevents evaporation and controls environmental pollution that has reached a level that can no longer be ignored.

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