Ultralow oxygen treatment for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on iceberg lettuce I. Effects of temperature, time, and oxygen level on insect mortality and lettuce quality

Ultralow oxygen (ULO) treatments with different oxygen levels, treatment times, and temperatures were studied to determine effects on western ower thrips mortality and postharvest quality of iceberg lettuce. Thrips mortality increased with reduced oxygen level and increased treatment ime and temperature. At 0.003% oxygen, over 99.6% mortality rates of thrips were achieved in three ULO treatments of 2, 3, and 4 d at 10, , and 1 ◦C, respectively. No treatments caused injury to lettuce surface leaves and there was no reduction in visual quality for treated lettuce. owever, about 9–33% of lettuce heads sustained injury to heartleaves. The 2 d ULO treatment with 0.003% oxygen had the lowest injury rate to eartleaves and the injury increased with increased treatment duration. The amount of injured leaves was small (<2 g per head). There were also ome variations among the lettuce cultivars in susceptibility to heartleaf injury by ULO treatments. Four out of eight cultivars tested tolerated the d ULO treatment at 10 ◦C without any injury. Therefore, ULO treatment has potential to be developed as an alternative postharvest treatment for estern flower thrips on iceberg lettuce. ublished by Elsevier B.V.