Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/25/2007
Publication Date: 3/20/2008
Citation: Liu, Y. 2008. Ultralow oxygen treatment for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on iceberg lettuce. I. Temperature, time & oxygen level on insect mortality & lettuce quality. Postharvest Biology and Technology. 49:129–134. Interpretive Summary: Results from controlled atmosphere studies on postharvest control of western flower thrips on iceberg lettuce were reported. Close to complete control of thrips was achieved with 2, 3, and 4 day ultralow oxygen treatments at 10, 5, and 1C respectively. However, the treatments also resulted in minor injuries to lettuce heartleaves. The proportion of lettuce heads injured varied with treatment and lettuce cultivar. The 2 day treatment at 10C was safest and 4 out of 8 cultivars tolerated the treatment. The treatment seems to have good potential to be further developed for postharvest control of western flower thrips on iceberg lettuce.
Technical Abstract: Ultralow oxygen (ULO) treatments with different oxygen levels, treatment times, and temperatures were studied to determine responses of western flower thrips and effects on postharvest quality of iceberg lettuce. Over 99.6% mortality rates of thrips were achieved in three ULO treatments of 2, 3, and 4 days at 10, 5, and 1 degree C respectively. All treatments did not cause injury to lettuce surface leaves and there was no reduction in visual quality of lettuce. However, about 9 to 33% of lettuce heads sustained injury to heartleaves. The 2 day treatment had the lowest injury rate and the injury increased with treatment duration. The amount of injured leaves was small (<2 g/head). There also seems to be variation among the lettuce cultivars tested. Four out of eight cultivars tested tolerated 2 day ULO treatment at 10 degrees C without any injury whereas the other four cultivars showed significant damage. Therefore, ULO treatment has potential to be developed as an alternative postharvest treatment for western flower thrips on iceberg lettuce.