Comparison of efficacy of nitric oxide fumigation under nitrogen and carbon dioxide atmospheres in controlling granary weevil (Sitophilus granaries) and confused flour beetle (Tribolium confusum)

Authors: Liu, Yong Biao

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2020
Publication Date: 8/15/2020
Citation: Liu, Y.-B. 2020. Comparison of efficacy of nitric oxide fumigation under nitrogen and carbon dioxide atmospheres in controlling granary weevil (Sitophilus granaries) and confused flour beetle (Tribolium confusum). Journal of Stored Products Research. 88. https://doi.org/10.1016/j.jspr.2020.101672.
DOI: https://doi.org/10.1016/j.jspr.2020.101672

Interpretive Summary: Nitric oxide (NO) is a new fumigant for postharvest pest control. NO fumigation must be conducted under ultralow oxygen (ULO) conditions because NO reacts with O2 to form NO2. So far, N2 has been used to establish ULO for NO fumigation. In this study, CO2 and N2 were used to establish ULO conditions for NO fumigation to determine if CO2 will affect efficacy of NO fumigation against granary weevil and confused flour beetle. In 12 h fumigations, there were no significant differences in mortality of adults, larvae, and pupae between NO fumigations under CO2 and N2 atmospheres between the two insects. However, the two species had differences in tolerance to NO fumigation. Granary weevil pupa was the most tolerant life stage to NO fumigation while confused flour beetle egg was the most tolerant life stage to NO fumigation. Twenty-four hour fumigations with 2.0 and 1.0 % NO achieved over 99% and 100% of all life stages of granary weevil and confused flour beetle, respectively. This study demonstrated that both N2 and CO2 can be used to establish ULO for NO fumigation and effective NO fumigation treatments for the two stored product insects were identified. The study demonstrated that NO fumigation has potential to control stored product insects.

Technical Abstract: Nitric oxide (NO) was a recently discovered fumigant for postharvest pest control. Because NO reacts with oxygen (O2) spontaneously to form nitrogen dioxide (NO2), NO fumigation must be conducted under ultralow oxygen (ULO) atmospheres to preserve NO and nitrogen (N2) has been used to establish ULO atmospheres in NO fumigation studies in the past. However, carbon dioxide (CO2) can also be used to ULO atmospheres and CO2 fumigation was also reported to be effective in controlling certain insect pests and enhancing toxicity of some fumigants. In the present study, NO fumigations under ULO conditions established with N2 and CO2 were compared for effects against granary weevil, Sitophilus granaries, and confused flour beetle, Tribolium confusum. All life stages of the two insects were subjected to 12 h fumigation treatments with 0.5 to 1.0% NO at 25°C under ULO established with CO2 (NO-CO2 treatments) and N2 (NO-N2 treatments). The most tolerant life stage for each species in each fumigation treatment was then fumigated with NO for 24 h fumigation at 25°C to determine an effective treatment. There were no significant differences in mortalities of adults, larvae, and pupae at all NO concentrations between ULO conditions established with CO2 and N2 for either insect. NO-CO2 was, however, significantly less effective than NO-N2 against eggs of both species. Granary weevil pupae and confused flour beetle eggs were the most tolerant stages for each respective species to NO fumigation: >99% mortality of granary weevil pupae and confused flour beetle eggs were, however, achieved in the 24 h fumigation with 2% and 1% NO, respectively. This study showed that CO2 can be used to establish ULO atmospheres for NO fumigation, but did not significantly contribute to insect mortality.