Ultralow oxygen treatment for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on iceberg lettuce: II. Effects of pre-treatment storage on lettuce quality

Iceberg lettuce stored under normal atmosphere and controlled atmosphere (CA) with about 3% oxygen at low temperature for 1 week was compared with fresh lettuce for their response to 2 d ultralow oxygen (ULO) treatment with 0.003% oxygen at 10 °C for control of western flower thrips. Lettuce which had been stored for 1 week under normal or CA tolerated ULO treatment while over 30% of fresh lettuce sustained minor injury to heartleaves. Therefore, pre-treatment storage at low temperature enhanced tolerance of lettuce to the subsequent insecticidal ULO treatment. A sequential combination of CA storage and ULO treatment was demonstrated to be effective against western flower thrips and lettuce aphid and safe to all seven lettuce cultivars tested. The study indicated that ULO treatment can be made safer to lettuce through pre-treatment storage to increase lettuce tolerance.