Response of california citrus to postharvest phytosanitary treatments

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

Submitted to: Citrograph
Publication Type: Trade Journal
Publication Acceptance Date: 2/1/2021
Publication Date: 3/1/2021
Citation: Arpaia, M., Cranney, J.R., Tebbets, J.S., Walse, S.S., Obenland, D.M. 2021. Response of california citrus to postharvest phytosanitary treatments. Citrograph. 12(2):30-37.

Interpretive Summary: Export markets are a critical part of the California citrus industry’s marketing plan for the fresh citrus crop. This fruit must meet the standards of the importing country, which can include agreements to control quarantine pests with methyl bromide fumigation “on arrival” in the export country or a “pre-departure” phosphine fumigation. Fumigation can harm fruit quality under certain conditions and cold temperatures can injure citrus fruit. Low temperature treatments, which maintain fruit pulp temperature below a specified minimum, are an option, but the risk of chilling injury needs to be considered. The primary purpose of this study was to confirm that phosphine fumigation and a specific range of cold temperatures do not harm fruit quality. In this study we examined the response of California citrus to methyl bromide fumigation, three approved phosphine treatments, and a low temperature (34°F) treatment to simulate a possible quarantine cold schedule for fruit flies, which were compared to a non-treated control. Results indicate that none of the phosphine treatments or the cold-temperature treatment impacted marketability or sensory quality of any of the fruit studied. Peel damage and increased decay was observed due to a stand-alone methyl bromide treatment in all citrus except for Valencia orange when the fruit were held under a two-week simulated marketing conditions. Additionally, eating quality of both grapefruit and mandarins was reduced following the methyl bromide fumigation.

Technical Abstract: Export markets are a critical part of the California citrus industry’s marketing plan for the fresh citrus crop. This fruit must meet the phytosanitary standards of the importing country, which can include agreements to control quarantine pests with methyl bromide fumigation “on arrival” in the export country or a “pre-departure” phosphine fumigation. Fumigation can harm fruit quality under certain conditions and cold temperatures can injure citrus fruit. Low temperature treatments, which maintain fruit pulp temperature below a specified minimum, are an option, but the risk of chilling injury needs to be considered. The primary purpose of this study was to confirm that phosphine fumigation and a specific range of cold temperatures do not harm fruit quality. In a study funded by the USDA Technical Assistance for Specialty Crops (TASC) program, we examined the response of California citrus to methyl bromide fumigation, three approved phosphine treatments, and a low temperature (34°F) treatment to simulate a possible quarantine cold schedule for fruit flies, which were compared to a non-treated control. Results indicate that none of the phosphine treatments or the cold-temperature treatment impacted marketability or sensory quality of any of the fruit studied. Peel damage and increased decay was observed due to a stand-alone methyl bromide treatment in all citrus except for Valencia orange when the fruit were held under a two-week simulated marketing conditions. Additionally, eating quality of both grapefruit and mandarins was reduced following the methyl bromide fumigation.