2527 © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. Household and Structural Insects HPLC Analysis to Determine the Half-life and Bioavailability of the Termiticides Bifenthrin and Fipronil in Soil F. Manzoor 1 and M. Pervez Department of Zoology, Lahore College for Women University, Lahore, Pakistan, and 1 Corresponding author, e-mail: doc_farkhanda@ yahoo.com Subject Editor: Arthur Appel Received 29 September 2016; Editorial decision 15 March 2017 Abstract The aim of this study was to test the bioavailability and degradation in soil of the termiticides bifenthrin and fpronil, which are used to treat subterranean termites (Heterotermes indicola, Wasmann). Soil collected from different areas of Lahore was categorized as sandy clay loam (SCL) or sandy loam (SL). Laboratory bioassays were conducted to determine the bioavailability ratio of bifenthrin and fpronil in each type of soil after different periods of time. LT 50 values were determined posttreatment at different time intervals. Regarding soil type, both termiticides were more effective in SL soil, compared with SCL soil posttreatment. There were signifcant differences in termite mortality in treated compared with untreated control samples (P < 0.005). To test the degradation rate of soil termiticides, both qualitative and quantitative analyses were carried out by HPLC, and the effect of time on termiticide recovery rate determined. Calculated half-life values for bifenthrin (maximum, 1,002 and 1,262 d in SCL soil and SL soil, respectively) indicated that it persisted in both soil types at all concentrations. The maximum calculated half-life values of fpronil were 270 and 555 d in SCL and SL soil, respectively. At lower concentrations and over longer periods of time, fpronil completely degraded in SL soil, while a negligible amount was detected in SCL soil. Termiticide concentration decreased over time, as did the termiticide recovery rate. Overall, bifenthrin was more persistent than fpronil under all treatment conditions tested. Key words: high-performance liquid chromatography, half-life, bifenthrin, fipronil, lethal time Subterranean termites are challenging pests because of their small size, hidden nature, and tenacious foraging behavior. Different ter- mite control methods that have been adopted worldwide include physical barriers, baiting systems, and insecticides. The application of soil termiticides is common and is an effective measure for the control of building damage by these insects. Soil termiticides are used to generate barriers around and under buildings while foundations are being built (Spomer et al. 2009), and different types of liquid and dust termiticide formulations are used to treat foraging areas (Kubota et al. 2006). The various termiticide formulations used dif- fer in their effcacy. Numerous factors, including inadequate barrier thickness, chemical degradation, and absence of active ingredients relevant for the target organism, directly affect the bioavailability (the presence of the active ingredient residue of a particular insecti- cide or pesticide and its availability to the target insect in the soil) of termiticides to the target pest. Awareness of the bioavailability and degradation of each particular termiticide is important to deter- mine their effcacy and longevity in soil. Termiticide effcacy depends on soil type, pH, insecticide type, moisture, and temperature, all of which affect insecticide degradation, bioavailability, and effective- ness in the soil (Baker 2001). Pesticide bioavailability can be measured by particular response variables, such as mortality response, LC 50 , and LT 50 (Spomer et al. 2009). Degradation can be defned as the breakdown of a chemical to residues that differ from the parent elements from which they are derived. Pesticides that break down too rapidly may provide only short-term control. Chemical degradation occurs by photolysis, oxi- dation, and reduction reactions (Sassman et al. 2004), while biological degradation occurs through the action of environmental microorgan- isms (Nawab et al. 2003, Ghardiri and Rose 2001). The bioavail- ability of pesticides to target insects reduces as they degrade. The degradation of a pesticide in the soil is often described by its half-life, which is defned as the time taken for a chemical to degrade to half of its original concentration. The persistence, degradation, and mobility of pesticides are largely infuenced by their chemical properties. In soil, these chemicals are subjected to adsorption, plant uptake, weather, and soil conditions (Singh and Tandon 2015). Clay and sand content also affect soil termiticide effciency (Shemer and Linden 2006). Journal of Economic Entomology, 110(6), 2017, 2527–2533 doi: 10.1093/jee/tox249 Advance Access Publication Date: 11 October 2017 Research Article Downloaded from https://academic.oup.com/jee/article/110/6/2527/4431201 by guest on 15 June 2023