Implementation of an Indoxacarb Susceptibility Monitoring Program Using Field-Collected German Cockroach Isolates From the United States

Abstract

Indoxacarb, a sodium channel-blocking insecticide, has been in widespread use for German cockroach control in the United States since 2006. A two-tiered indoxacarb susceptibility monitoring strategy was previously developed as a first step toward determining indoxacarb susceptibility levels in German cockroach field populations. This strategy entails: (tier 1) testing field-collected populations in vial bioassays at two diagnostic concentrations; and (tier 2) testing populations at three diagnostic doses in oral (feeding) bioassays with treated bait matrix. In the current study the two-tiered technique was implemented to evaluate field (n = 14) and susceptible laboratory (n = 2) strains collected from 13 different U.S. locations. Our hypothesis was that at least some of the field-collected populations would display significant survivorship in both bioassays relative to susceptible laboratory populations. In agreement with this hypothesis, significantly reduced susceptibility was detected in 13 and 7 field strains with vial and feeding bioassays, respectively. In general, the lower number of strains displaying reduced susceptibility in feeding bioassays (seven strains) supports previous findings that indoxacarb is more toxic via ingestion. Although these findings suggest a reduced risk for resistance selection via feeding on indoxacarb-containing baits, they also suggest a need for proactive resistance management with respect to both spray and bait products.

Development of Diagnostic Insecticide Concentrations and Assessment of Insecticide Susceptibility in German Cockroach (Dictyoptera: Blattellidae) Field Strains Collected From Public Housing

“…Vial bioassays were used to monitor physiological resistance to the AIs, which is considered the most common category of resistance in cockroaches (Scharf et al 1998, Wang et al 2004, Gondhalekar et al 2013). Insecticide resistance can progress to problem levels quickly once physiological resistance is present at detectable levels (Ffrench-Constant & Roush 1990), even for baits.…”

“…Cockroach baits have been used in integrated pest management (IPM) as a cost-effective control strategy (Schal and Hamilton 1990, Wang and Bennett 2006). Despite the initial success of baiting in controlling cockroach populations and reducing resident exposure to insecticides, recent reports indicate cockroaches have developed resistance to newer bait AIs (Gondhalekar and Scharf 2012, Gondhalekar et al 2013, Ko et al 2016a). Historically, German cockroaches have been able to develop extensive resistance to different insecticides (Cochran 1995).…”

“…Historically, German cockroaches have been able to develop extensive resistance to different insecticides (Cochran 1995). Insecticide resistance in laboratory and field-collected German cockroaches has been reported for decades (Bennett and Spink 1968; Koehler and Patterson 1986; Cochran 1987; Umeda et al 1988; Cochran 1989; Hemingway et al 1993a, 1993b; Valles and Yu 1996; Lee et al 1996; Scharf et al 1997; Scharf et al 1998; Wei et al 2001; Holbrook et al 2003; Gondhalekar et al 2011, 2013; Ko et al 2016a; Naqqash et al 2016). In total, German cockroaches have shown resistance to 43 active ingredients (AIs) (Whalon et al 2016), and therefore, resistance management has become a priority in any cockroach IPM program.…”

“…Discriminating dose- or concentration-based approaches have been used successfully for detecting fipronil and indoxacarb resistance in German cockroach field strains (Holbrook et al 2003, Gondhalekar et al 2011, 2013). The research presented here targeted the problem in urban pest management posed by cockroach resistance, using an unprecedented resistance monitoring-based approach that included 14 AIs and a glass vial bioassay method.…”

“…Extensive prior research documented the vial bioassay method (e.g., Scharf et al 1999), which works based on cockroach tarsal contact with insecticide residues and ingestion via tarsal grooming (Scharf et al 1995). Diagnostic concentration (DC) bioassays are less labor-intensive and require fewer insects in comparison to the conventional resistance ratio method, which initially requires generation of concentration- or dose-mortality data for LC or LD estimation (Gondhalekar et al 2013). The goals of this study were to 1) develop DCs for commonly used cockroach insecticide AIs, and 2) test the DCs against cockroach strains collected from two multifamily housing sites in advance of field studies.…”