Low temperature phosphine fumigation of pre-chilled iceberg lettuce under insulation cover for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae).

Authors: Liu, Yong Biao

Submitted to: Journal of Asia-Pacific Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2011
Publication Date: 4/5/2011
Citation: Liu, Y. 2011. Low temperature phosphine fumigation of pre-chilled iceberg lettuce under insulation cover for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae). Journal of Asia-Pacific Entomology. 14:323-325.

Interpretive Summary: Low temperature phosphine fumigation has been reported to be safe and effective in controlling western flower thrips on fresh commodities including lettuce. However, commercial use of low temperature phosphine fumigation is hampered by the lack of low temperature fumigation chambers. In this study, we developed a low cost alternative fumigation method to conduct low temperature phosphine fumigation to control western flower thrips on iceberg lettuce. Pre-chilled lettuce on a pallet was fumigated under a cover of bubble insulation materials with foil surfaces at an ambient temperature of 20°C for 18 h. The fumigation successfully controlled thrips and did not cause any negative effects on lettuce quality. During fumigation, the temperature of lettuce only increased 2.7°C. The successful outcome of the study suggests that the method has potential to be used commercially and provides an economical alternative to conduct low temperature phosphine fumigation. The implication for controlling other pests on fresh commodities was also discussed.

Technical Abstract: Fumigation of chilled iceberg lettuce under an insulation cover was studied to develop economical alternatives to conduct low temperature phosphine fumigation for control of western flower thrips, Frankliniella occidentalis (Pergande), on exported lettuce. Vacuum cooled commercial iceberg lettuce on a pallet was sealed in a plastic bag and further sealed in a cover made of double layer bubble insulation with foil covers. Fumigation treatment was conducted at an ambient temperature of 20°C for 18 h. The phosphine concentration varied from about 1400 ppm at the start of fumigation to about 400 ppm at the end of fumigation. During the fumigation treatment, temperature of lettuce increased 2.7°C and the average temperature of lettuce was 5.5°C. The fumigation treatment achieved complete control of western flower thrips. Lettuce quality was evaluated 2 wk after fumigation and the fumigation treatment had no negative impact on lettuce quality. This study demonstrated that low temperature phosphine fumigation can be conducted on pre-chilled lettuce under an insulation cover. This method provided an economical and immediate solution for conducting low temperature phosphine fumigation without expensive low temperature fumigation chambers. The success of this method also suggests that existing commercial fumigation facilities, containers, and other sealable enclosures may also be modified by lining with insulation materials to become suitable for low temperature phosphine fumigation.