Efficacy and sorption of sulfur dioxide as a fumigant for control of navel orangeworm (Amyelois transitella) on stored pistachios

Authors: Liu, Yong Biao

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2023
Publication Date: 3/23/2023
Citation: Liu, Y.-B. 2023. Efficacy and sorption of sulfur dioxide as a fumigant for control of navel orangeworm (Amyelois transitella) on stored pistachios. Journal of Stored Products Research. 102. Article 102109. https://doi.org/10.1016/j.jspr.2023.102109.
DOI: https://doi.org/10.1016/j.jspr.2023.102109

Interpretive Summary: There is a need for safe and effective alternative treatments for stored product insects including navel orangeworm (NOW). Sulfur dioxide (SO2) is a GRAS (generally recognized as safe) compound and has been used widely to preserve food products but has not been used for postharvest pest control on stored products. In this study, SO2 fumigation was evaluated for controlling NOW on pistachios. SO2 was adsorbed rapidly after injection and, therefore, 3 h short fumigations with SO2 at different concentrations were evaluated for effects against eggs, larvae, and pupae of NOW. The different life stages differed in susceptibility to SO2 fumigation. Complete controls of eggs, larvae, and pupae were achieved in 3 h fumigations with 0.2, 2.0, and 1.0% SO2. In large-scale fumigation tests, 3 h fumigation with 1.6-1.8% SO2 resulted in complete control of NOW larvae. Therefore, SO2 fumigation has potential to be used to control NOW on stored pistachios and is likely to be effective against other insects on stored products.

Technical Abstract: Sulfur dioxide (SO2) fumigation was evaluated for postharvest control of navel orangeworm (NOW), Amyelois transitella, on stored pistachios in a laboratory study. Sorption of SO2 on pistachios were measured at 5, 15, and 25°C. Because rapid sorption of SO2 on pistachios after SO2 injection, 3 h short fumigations were evaluated to determine effective treatments against NOW eggs, larvae, and pupae. SO2 fumigation was effective against all of the life stages tested. However, larvae in infested pistachios were most tolerant and eggs were most susceptible to SO2 fumigation. Complete controls of eggs, larvae, and pupae were achieved in 3 h fumigations with 0.2, 2.0, and 1.0% SO2. Large SO2 fumigation trials each with 4.5 kg pistachios were conducted and complete control of NOW larvae were achieved in 3 h fumigation with about 1.6-1.8% SO2 at ambient temperatures of 18-21°C. The results showed that SO2 fumigation has potential to control NOW on stored pistachios as well as to control other postharvest pests on stored products.