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 ( $\overline{x}\pm 2s$ ) 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 ( $\overline{x}\pm 2s$ ). 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.

Keywords: BMSB; eFUME; ethyl formate; postharvest fumigation.