Field Distance Effects of Fipronil and Chlorfenapyr as Soil Termiticides Against the Desert Subterranean Termite, Heterotermes aureus (Blattodea: Rhinotermitidae)

Abstract

A desirable trait of termiticides is that they suppress termite activity at a distance from the site of application. Fipronil and chlorfenapyr are two non-repellent termiticides that display delayed toxicity and are therefore good candidates for yielding distance effects. We assessed their effects as soil-applied termiticides for the management of the desert subterranean termite, Heterotermes aureus (Snyder), under field conditions in southern Arizona. Our approach involved recording termite activity within field experimental grids consisting of termite monitoring stations at selected distances from a termiticide application perimeter. Fipronil-treated plots experienced large and significant reductions in termite presence and abundance relative to controls in stations immediately adjacent to treated soil. However, there was no evidence of reductions in termite activity in stations further away from the soil treatment. In contrast, termite abundance and presence in stations decreased relatively to controls after chlorfenapyr application in whole experimental grids and in several grid sections spatially separated from treated soil. These reductions were especially evident in the five central stations surrounded by the treatment perimeter and in the furthest set of stations. The spatial pattern of changes in chlorfenapyr plots was consistent with termiticide transfer as a mechanism behind distance effects. The impact of fipronil and chlorfenapyr on termite populations in our study suggests that they can both be useful for the management of H. aureus, although each might be suited for differentmanagement goals. Our results also suggest that perimeter treatments alone are not sufficient to accomplish full control of large H. aureus infestations.