Concentration-Dependent Degradation of Three Termiticides in Soil Under Laboratory Conditions and Their Bioavailability to Eastern Subterranean Termites (Isoptera: Rhinotermitidae)

Authors

Raj K. Saran, McLaughlin Gormley King CompanyFollow
Shripat T. Kamble, Universitiy of Nebraska--LincolnFollow

Document Type

Article

Date of this Version

2008

Comments

Published in J. Econ. Entomol. 101(4): 1373-1383 (2008) Copyright 2008 Entomological Society of America Used by permission

Abstract

Degradation and bioavailability of imidacloprid, fipronil, and bifenthrin applied at label rates ([AI], wt:wt in soil) in the loamy soil of Nebraska were determined over a 6-mo duration. Based on the calculated half-lives of the three termiticides, it was concluded that the degradation rate was lowest when a termiticide was applied at the highest label rate. Bioassays of Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) conducted at 8, 31, 65, 90, 135, 160, and 180 d posttreatment showed an inverse relationship between the LT₉₀ values and the variable concentrations. At day 180, exposures to all the termiticide-treated soil samples (concentration × termiticide) resulted in 100% mortality of R. flavipes workers. However, lower LT₉₀ values were observed for termites exposed to soils treated with highest label rates even when the treated soils were aged in the lab for 6 mo. This suggested a higher bioavailability of these three termiticides when applied at higher application rates. Termite mortality was fastest for bifenthrin followed by fipronil and imidacloprid.