Rapid degradation of termiticides under field conditions

Abstract

Soil testing is used by regulatory agencies to determine the adequacy of termiticide application by pest controllers. Because tests may be carried out years after treatment, an accurate knowledge of termiticide degradation rates is crucial if determinations are to be valid. Degradation of exposed residues of bifenthrin, chlorfenapyr, chlorpyrifos, fipronil and imidacloprid was investigated in a field trial conducted near Narrandera (inland New South Wales) and in Sydney. Samples of soil 75 mm deep were collected immediately after treatment and after 12 months from plots treated with termiticides to a minimum depth of 350 mm and analysed for termiticide residues. Bifenthrin and chlorfenapyr were the most persistent termiticides. Losses of chlorpyrifos exceeded 99% at both locations. Losses of fipronil and imidacloprid were 96% and 94%, respectively, at Narrandera and 67% and 50%, respectively, in Sydney. To explore the fate of chlorpyrifos, fipronil and imidacloprid in the soil profile at Narrandera, samples were collected 15 months after treatment to a depth of 450 mm, in 150 mm increments, from plots treated to a depth of 700 mm. In soil below 150 mm, chlorpyrifos and fipronil content was little changed from time of application whereas major losses of imidacloprid had occurred at all depths. These findings have implications for termite treatment regulation in Australia. Regulatory agencies have relied upon degradation rates observed in laboratory experiments to determine in situ treatment adequacy. Results of this field study suggest that termiticides can degrade more rapidly in situ than indicated by laboratory experiments.

Modeling Adsorption-Desorption Kinetics of Imidacloprid in Soils

“…Cox et al (1997) conducted sorptiondesorption of imidacloprid and its three metabolites and reported that metabolites such as the imidacloprid-guanidine, possibly produced in our experiment, are more strongly sorbed with the soil matrix compared with the main compound and less reactive in the case of imidacloprid-urea. Recent studies focused on the degradation of imidacloprid under laboratory and field conditions (Horwood, 2007;Anhalt et al, 2008). In these studies, imidacloprid metabolites were not quantified.…”

“…Imidacloprid is a commonly used insecticide as a soil and foliar treatment for a wide range of crops (Grey et al, 2006;Kreutzweiser et al, 2008). It is effective for sucking insects, soil insects, termites, and several species of biting insects (Horwood, 2007).…”

Control of Subterranean Termites (Isoptera: Rhinotermitidae) Infesting Power Poles

“…Such behavior is not surprising with repellent chemicals such as bifenthrin (Smith and Rust 1990) but is less well documented for so-called nonrepellents such as chlorfenapyr (Rust and Saran 2006), Þpronil (Ibrahim et al 2003), and imidacloprid (Gahlhoff and Koehler 2001). Chemical breakdown is unlikely to have been the cause of differences in effectiveness among soil treatments, because bifenthrin and chlorfenapyr, the two least active soil treatments, were shown by Horwood (2007) to have the greatest Þeld longevity of the liquid termiticides tested.…”

Effect of Sub Lethal Concentrations on Population Size of Termites Odontotermes Obesus (Rambur) and Coptotermes Heimi (Wasmann) Under Laboratory and Field Conditions

“…Horwood [29] found that after 15 months, chlorpyrifos and fipronil concentrations at lower depths were little changed from the time of treatment, but there was a major reduction in imidacloprid concentration at all depths. Cai and Henderson [30] their results show that the presence of C. formosanus can suppress the growth of Bti and Btt and the suppression effect enhanced with increased of group size.…”