Procedures of Laboratory Fumigation for Pest Control with Nitric Oxide Gas

Abstract

Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control. This paper provides detailed protocols for conducting NO fumigation on fresh products and procedures for residue analysis and product quality evaluation. An airtight fumigation chamber containing fresh fruit and vegetables is first flushed with nitrogen (N2) to establish an ultralow oxygen (ULO) environment followed by injection of NO. The fumigation chamber is then kept at a low temperature of 2 - 5 °C for a specified time period necessary to kill a target pest to complete a fumigation treatment. At the end of a fumigation treatment, the fumigation chamber is flushed with N2 to dilute NO prior to opening the chamber to ambient air to prevent the reaction between NO and O2, which produces NO2 and may damage delicate fresh products. At different times after NO fumigation, NO2 in headspace and nitrate and nitrite in liquid samples were measured as residues. Product quality was evaluated after 2 weeks of post-treatment cold storage to determine effects of NO fumigation on product quality. Keeping O2 from reacting with NO is critical to NO fumigation and is an important part of the protocols. Measuring NO levels is challenging and a practical solution is provided. Possible protocol modifications are also suggested for measuring NO levels in the fumigation chambers as well as residues. NO fumigation has the potential to be a practical alternative to methyl bromide fumigation for postharvest pest control on fresh and stored products. This publication is intended to assist other researchers in conducting NO fumigation research for postharvest pest control and accelerating the development of NO fumigation for practical applications.

Nitric oxide fumigation for postharvest pest control on lettuce

“…The fumigation chambers were then sealed and flushed with N 2 gas to establish ULO conditions with ≤35 ppm O 2 . An O 2 analyzer (Series 800, IL Instruments, Inc., Johnsburg, IL, USA) was used to monitor O 2 levels in the fumigation chambers . NO was then taken using an airtight syringe from a pre‐loaded foil bag and injected into the fumigation chambers to establish the pre‐calculated concentration of 1.0%, and 2.0% based on volume (V NO :V chamber ).…”

“…The NO was then injected to establish the pre‐calculated NO concentration of 0.5% based on volume. During the fumigation treatment, a flue gas meter (Kane 900, Kane International Ltd., Welwyn Garden City, Hertfordshire, UK) in combination with a dilution device was used to measure NO concentration as described earlier at the beginning and the end of the fumigation treatment to assure no leakage of the fumigation chamber. At the end of each fumigation treatment, the chamber was flushed with N 2 gas at 15 L min −1 flow rate to dilute NO before opening for aeration.…”

“…Nitric oxide fumigation is effective against a wide variety of pests at various life stages including western flower thrips and lettuce aphid . Small‐scale laboratory NO fumigation treatments were also demonstrated to be safe to all fresh products tested to date . NO fumigated strawberries and apples also have better postharvest quality as compared with untreated controls .…”

“…However, because NO reacts with oxygen (O 2 ) to produce nitrogen dioxide (NO 2 ), a brown gaseous chemical that is harmful to fresh vegetables and fruits, NO fumigation must be conducted under ultralow oxygen (ULO) conditions . At the end of treatment, the fumigation chamber must be flushed with nitrogen (N 2 ) to dilute NO before opening for aeration to prevent NO 2 production and likely injuries to fresh products …”

Methyl benzoate fumigation for control of post‐harvest pests and its effects on apple quality

“…Other alternatives such as ethyl formate and sulfuryl fluoride have very limited potential for post-harvest pest control due to phytotoxicity to fresh products or/and ineffectiveness (Aung, Leesch, Jenner, & Grafton-Cardwell, 2001;Bell, Savvidou, & Wontner, 1998;Zoffoli, Michelow, & Naranjo, 2013). The newly discovered fumigant nitric oxide is an effective and safe alternative but is not available for commercial use and also has complex fumigation procedures (Liu, 2013;Liu & Yang, 2016;Liu, Yang, & Masuda, 2017). Effective and safer alternatives are, thus, still needed for post-harvest pest control, including both fresh and stored products.…”