Fresh grapefruit consumers are trained to expect vivid yellow-orange peel color, depending on the variety, even though peel color has little to do with internal maturity or quality. The greasy spot rind blotch disease has been in Florida for many years, ascribed to a fungal pathogen called Zasmidium citri-griseum (previously named Mycosphaerella citri). Besides causing defoliation, it also mars the peel with tiny black specks that cause the rind to remain green, even after degreening. The spots can coalesce into black patches in extreme cases, sometimes called “pink pitting” or greasy spot rind blotch. Growers had this disease under good management, but within the past five years, fruit with similar symptoms started appearing as early as November, when nighttime temperatures are low, and peel color should improve instead of regreening. The symptoms are like greasy spot rind blotch, but there are few to no symptoms on the leaves of the same trees. Thus, the industry generally refers to the disorder as “greasy green” until a more definitive identification of the causal agent and disease development is determined. In a 2021 grower survey, 89% of respondents experienced the disorder to some extent, with packers reporting losses ranging between $20,000 and $1.7 million. There was no consensus among growers and packers regarding the cause of greasy green or the factors contributing to the problem. While studies are underway to determine if the disorder is indeed related to greasy spot rind blotch, studies were initiated to determine if affected fruit could be degreened effectively, as many packers often ended up abandoning degreening attempts on affected fruit and not using them for the fresh market. Our tests found that even after degreening (5 ppm ethylene at 27oC) red and white grapefruit for up to 5 days, their peel color still was not acceptable (
