Factors contributing to the "green ring" disorder of fresh market citrus

Mark A. Ritenour, Huating Dou


In 1998 and 1999, a significant number of early-season, drenched loads of citrus developed a new peel disorder called "Green Ring" (GR). Symptoms of the disorder were visible as rings or streaks on the peel that did not degreen or were brown and sunken. Symptoms were generally associated with contact points with other fruit or with the bin sides or bottom. GR has been observed on 'Fallglo' and 'Sunburst' tangerines, 'Navel' oranges and red and white grapefruit. In 'Ruby Red' grapefruit, smaller fruit tended to develop more GR than larger fruit. Fruit from a variety of different truck or bin drenchers on the East cost developed GR but the disorder was not associated with a particular drench company. Furthermore, during both seasons, incidence of GR declined as the season progressed into November, with no known reports of GR by December. This suggests that preharvest/deveiopmental factors such as maturity, cultural practices, weather conditions, etc., play a critical role in GR development. Preharvest experiments were conducted to test which drench chemicals or possible contaminants might be involved in GR development. During postharvest treatments, no GR developed when fruit were dipped in water or water with 125 ppm chlorine. However, significant GR developed when solutions contained different combinations of surfactant, thiabendazole (TBZ), chlorine, break fluid and/or motor oil. Although the disorder is usually visible before packing, preliminary data suggest that waxing may reduce GR severity after storage.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283