Submitted to: Intech
Publication Type: Book / Chapter
Publication Acceptance Date: 7/29/2011
Publication Date: 2/8/2012
Citation: Wiltz, B. A. 2012. Factors Affecting Performance of Soil Termiticides, pp. 153-170. Insecticides: Basic and Other Applications, S. Soloneski and M. Larramendy (Ed.), ISBN: 978-953-51-0007-2, InTech.
Interpretive Summary: Several long-term studies have shown that termiticide longevity depends on both location and termiticide class. Factors contributing to the availability and persistence of termiticides include soil-termiticide interactions, application technique, environmental factors, and termite pressure and susceptibility. Because performance is so dependent on a combination of temiticide and soil properties and weathering, more research is needed to evaluate new and existing products under a larger range of conditions. Soil termiticides have been extensively evaluated for toxicity, bioavailability, and degradation. However, reasons for termiticide failure are complex and often local in nature, indicating the need for more research and localized treatment recommendations regarding choice of toxicant, application technique, and treatment frequency.
Technical Abstract: Applying liquid insecticide to soil under and around structures is one of the most widely used methods of subterranean termite prevention and control. Failure of soil termiticide treatments is often related to factors other than the active ingredient. Efficacy and longevity of soil treatments vary greatly with soil properties, termiticide application rate, application technique, and termite pressure. Moisture, temperature, and microbial communities also help determine the success or failure of an insecticide treatment. Because soil consists of a heterogeneous mixture of mineral and organic particles, it is difficult to predict the influence of soil type on termiticides. When soil conditions fall outside an optimum range, termiticides can be immobilized or adsorbed by the soil or altered chemically to an inactive form. Numerous laboratory studies have found interactions between soil and termiticide properties. Termiticide effectiveness diminishes over time, especially on soils that pose bioavailability problems. There is evidence that even with slow acting, non-repellent termiticides, horizontal transfer of termiticide among foragers is limited to a few meters from the treated barrier. This limited potential for transfer emphasizes the importance of bioavailability of termiticides in soil over an extended period of time. Application rate affects both initial availability and degradation rate. Within certain ranges of application rates, availability increases with rate; however, the opposite is true at other rates. In addition to affecting bioavailability, high termiticide concentrations may indirectly affect degradation by negatively impacting bacterial and fungal populations, resulting in prolonged inhibition of soil dehydrogenase and esterase activities. In addition to properties of the soil and chemicals, variations in application technique can influence availability, persistence, and impenetrability of toxins. Such variables include gaps in soil treatment, thickness of treated layer, and watering method.