Ethyl formate dilution in carbon dioxide for fumigation control of the brown marmorated stink bug Halyomorpha halys, Stål (Hemiptera: Pentatomidae)

Abstract

BACKGROUND The brown marmorated stink bug (BMSB), Halyomorpha halys, has caused significant agricultural damage to numerous hosts, so agricultural producers seek to limit its spread. Where established, BMSB can also cause substantial urban and commercial disturbance, as overwintering adults may seek refuge inside dwellings, covered spaces, vehicles, and consignments. Phytosanitary authorities are most concerned with the importation of ‘hitchhiking’ adults in this refugia, with certain countries requiring a quarantine treatment to mitigate risk. This study explores fumigation with ethyl formate, applied as 16.7% by mass dilution in carbon dioxide, for control of adult BMSB. RESULTS The induction of diapause, to simulate overwintering physiology, resulted in 2‐ and 3‐fold increases in the tolerance of adults toward this ethyl formate fumigation at 10 ± 0.5 °C (truex¯±2s) lasting for 8 and 12 h, respectively. However, a decreased tolerance (0.7‐fold) of diapausing specimens was observed for a 4‐h duration. Diapausing and nondiapausing adult BMSB can be controlled at the probit 9 level if the headspace concentration of ethyl formate, [EF], in the carbon dioxide mixture is maintained ≥7.68 mg L−1 for 12 h at 10 ± 0.5 °C (truex¯±2s). If the duration is shortened to 4 h, [EF] must be maintained ≥14.73 mg L−1 over the course of fumigation. CONCLUSION The toxicity of ethyl formate in this mixture can be distinct for different physiological states of the same life stage, as evidenced by a ca. 3‐fold increase in the Haber's z parameter for adult BMSB when in diapause. Respective to the physiological state of adults, this study identifies how the applied dose and/or treatment duration can be modulated (i.e. tuned) to ensure adequate toxicological efficacy toward BMSB infesting hosts or refuge at temperatures ca. >10 °C. Published 2022. This article is a U.S. Government work and is in the public domain in the USA.

Confirmatory evaluation of eFUME for control of brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae)

“…The mortality of diapausing adult H. halys during confirmatory Trials 1, 2, and 3 were consistent with the laboratory results of Kawagoe et al (2022) as well as McKirdy (2022), as complete mortality of 1,053, 1,114, and 1,172 specimens was observed, respectively, when treatment temperature was maintained just above 10°C ( T Σ ± s ; Trial 1: 10.3 ± 0.2; Trial 2: 10.1 ± 0.3; Trial 3: 10.0 ± 0.4°C, respectively (Table 2). Corresponding survivorship of nontreated controls was 95.67%, 100.00%, and 99.23%, respectively (Table 2).…”

“…Accordingly, EF was applied steady-state, [EF] ss , for a duration of 4 h at a target dosage of 14.5 mg/liter with the intent of yielding a Ct exposure of ca. 58 mg/liter h, which was predicted to control H. halys at probit 9 level (Kawagoe et al 2022). To ensure that [EF] was maintained at the 14.5 mg/liter target, the applicator was turned on for 10 seconds, to release ca.…”

“…14.5 mg/liter should be applied to compensate for potential EF loss within the enclosure. For example, after careful consideration of logistical, operational, and regulatory constraints as described by Kawagoe et al (2022), MPI (2023) recently approved an EF treatment for the H. halys control in containers and vehicles, whereby an initial dosage of 20 mg/liter is applied for 4 h at ≥ 10°C, with a minimum final reading of at least 15 mg/liter, and a targeted Ct exposure of 65 mg/liter h.…”

“…Detector response and retention indices were determined in trial-specific calibration studies by diluting known volumes of EF into volumetric gas vessels. A response curve was generated respectively to each fumigation trial with each sample referenced to the response (Kawagoe et al 2022). [EF] responses were recorded to the nearest tenth mg/liter for each sampling location at each temporal interval for each trial ( vide infra ).…”

“…From the perspective of an on-arrival treatment in AUS and NZ, ethyl formate (EF), commercially formulated as a 16.7% by mass dilution in carbon dioxide and licensed as eFUME (Draslovka Services LTD., North Melbourne, AUS), has the required registration and therefore could be used to control adult H. halys in the risk pathway described above (Ormsby 2018, Hallet 2019). In fact, MPI has recently approved a 4-h eFUME schedule (MPI 2023) based principally on the laboratory-scale results of Kawagoe et al (2022), which identified efficacious fumigation parameters via Haber's rule, at least for greenhouse-reared H. halys , and discussed the potential contribution(s) of carbon dioxide toward this end. Here we expand on that work by conducting triplicate confirmatory trials in which ca.…”