Fumigating citrus with phosphine does not impact marketability or eating quality

Authors: Obenland, David - Dave; CRANNEY, JAMES - CALIFORNIA CITRUS QUALITY COUNCIL; TEBBETS, JOHN; Walse, Spencer; ARPAIA, MARY LU - UNIVERSITY OF CALIFORNIA

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2021
Publication Date: 8/10/2021
Citation: Obenland, D.M., Cranney, J., Tebbets, J.S., Walse, S.S., Arpaia, M. 2021. Fumigating citrus with phosphine does not impact marketability or eating quality. Plant Health Progress. 22(4):516-523. https://doi.org/10.1094/PHP-03-21-0053-RS.
DOI: https://doi.org/10.1094/PHP-03-21-0053-RS

Interpretive Summary: Phosphine fumigation is currently being adopted by the California citrus industry to satisfy the desires of trading partners to eliminate the use of methyl bromide, the current standard for quarantine treatment for citrus. The question existed, however, whether phosphine harms citrus fruit quality. In an extensive study lemons, grapefruit, navel and Valencia oranges and mandarins were fumigated with phosphine, using the most likely to be used treatments at three different times during the season. Methyl bromide fumigation and low temperature treatment were included as comparisons. After fumigation the fruit were stored for 4 weeks at a cold temperature appropriate for the citrus type, followed by 1 week at 10°C + 1 week at 20°C to simulate marketing and then evaluated for external and internal quality, the quality measurements being complemented by sensory evaluations of appearance and flavor. Results indicated that phosphine did not harm quality in any of the citrus types in contrast to methyl bromide, which was often damaging to lemons and grapefruit.

Technical Abstract: To ensure control of arthropod pests, fresh citrus exports from the USA may be subject to a postharvest phytosanitary treatment. These treatments, however, can sometimes cause a phytotoxic response and damage the fruit. The main purpose of this study was to confirm that phosphine fumigation does not impact either marketability or eating quality of citrus. Methyl bromide (MB) fumigation and low temperature treatment were included in the testing as comparisons. Treatments were examined in the context of a simulated oceanic treatment of 28-d followed by 1 week at 10°C and then 1 week at 20°C to typify distribution and marketing conditions over the course of each citrus type’s export period. Key quality parameters were evaluated for each of three “pre-departure” phosphine fumigations or an “on arrival” MB fumigation or a 28-d low temperature treatment at 1'C and compared to non-treated controls. In the second year, navel oranges were further evaluated using a sequential treatment where a “pre-departure” phosphine fumigation was followed by the “on arrival” MB fumigation. This work is the first to present results comparing phytosanitary treatments over multiple kinds of citrus and indicated that the phosphine treatments did not alter marketability or sensory quality for any of the citrus types. This contrasted with MB fumigation that was damaging to the peel of all citrus, except Valencia oranges, and harmed grapefruit and mandarin flavor.