Fumigation with Phosphine for Postharvest Insect Control on Lettuce, Broccoli, and Strawberries

Authors: Liu, Yong Biao

Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: 10/20/2007
Publication Date: 11/20/2007
Citation: Liu, Y. 2007. Fumigation with Phosphine for Postharvest Insect Control on Lettuce, Broccoli, and Strawberries. Proceedings of International Research Conference on Methyl Bromide Alternatives.

Interpretive Summary: Western flower thrips is a common pest of lettuce, broccoli, and strawberries in California but a quarantined insect in some overseas markets and therefore affect U.S. export of infested products. Fumigation with pure phosphine at low temperature was studied to control thrips on lettuce, broccoli, and strawberries. Different combinations of dose and treatment time were tested. Western flower thrips were very susceptible to phosphine fumigation treatments. Fumigation treatment with 250 ppm phosphine for 18 hours at low temperature of 2°C was sufficient to control western flower thrips. One fumigation treatment with 1000 ppm phosphine was tested on romaine and head lettuce and on broccoli. One day fumigation treatments with 500 and 1000 ppm phosphine were tested strawberries. All fumigation treatment resulted in complete control of thrips and had no negative effects on postharvest quality of the products. Therefore, pure phosphine fumigation at low temperature is promising for quarantine control of western flower thrips on lettuce, broccoli, and strawberries.

Technical Abstract: U.S. exported lettuce, broccoli, and strawberries often harbor western flower thrips (Frankliniella occidentalis), a quarantined pest in Taiwan, and therefore require quarantine treatment. Pure phosphine fumigation at a low temperature of 2°C was studied as an alternative to methyl bromide to control western flower thrips. Complete control of thrips was achieved in fumigation treatments of 18 hour or longer with 250 ppm or higher phosphine. One day fumigation treatment with 1000 ppm phosphine was tested on iceberg and romaine lettuce and on broccoli. One day fumigation treatments with 500 ppm and 1000 ppm phosphine were tested on strawberries. Visual quality for lettuce and broccoli was evaluated after two weeks of post-treatment storage. Strawberry quality was evaluated after one week of post-treatment storage. For all the products, there were no significant differences between the treatments and the controls in postharvest quality and there were no injuries caused by the fumigation treatments. Therefore, pure phosphine fumigation at low temperature was promising for postharvest control of western flower thrips on lettuce, broccoli, and strawberries.