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<p>The fungal pathogen <i>Rhexocercosporidium carotae</i> causes black spots on cold stored carrots. Black spot incidence on stored carrots ranged between 37 and 99% per year in a total of 76 field trials conducted 2011–2023 in Sweden. The disease is by far the most important disease of carrots in Sweden leading to substantial losses after storage. A survey of 104 Swedish carrot fields and the corresponding stored carrot lots 2006–2008 allowed to identify the most important variables related to black spot losses. The concentration of DNA of <i>R. carotae</i>, as determined by Taqman qPCR assays, in the canopy or on root surfaces in carrot crops at harvest, did not correlate with black spot incidence in the corresponding carrot lots after storage. Thus, knowledge of the presence of the pathogen at harvest could not be used to predict risks of post-harvest losses. Umbelliferous plants were found in field margins of 84% of the fields surveyed. The disease incidence of carrot lots from such fields was 23% higher compared to carrots from fields where umbelliferous plants were absent. Increase of the variables ‘number of growth days’ and ‘mechanical damage on the carrot surface during harvest’ resulted in significantly higher black spot incidence after storage. A series of field and storage experiments confirmed the effect of these variables. Even if the total gross yield of carrots increased by harvesting late, the marketable carrots decreased on average from 66% to 6.6% after storage in a year of high infection. This drastic yield reduction was solely due to black spot disease caused by <i>R. carotae</i>. Future guidelines for Integrated Crop Management (ICM) of carrots produced for&#xa0;cold storage should recommend the reduction of the number of growth days in combination with harvesting&#xa0;under optimum conditions as sustainable measures to ensure marketable yields.</p>

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Effect of cropping, harvesting, and storage conditions on black spots caused by Rhexocercosporidium carotae: almost two decades of research on the epidemiology of the major disease in Swedish cold-stored carrots

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  • 发表日期：

    2026年4月10日

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  • Mariann Wikström,
  • Sara Ragnarsson,
  • Jürgen Köhl,
  • Saskia Burgers,
  • Carolien Zijlstra,
  • Belia Hendrika Groenenboom-de Haas,
  • Bodil Jönsson,
  • Josefin Wikström

摘要

The fungal pathogen Rhexocercosporidium carotae causes black spots on cold stored carrots. Black spot incidence on stored carrots ranged between 37 and 99% per year in a total of 76 field trials conducted 2011–2023 in Sweden. The disease is by far the most important disease of carrots in Sweden leading to substantial losses after storage. A survey of 104 Swedish carrot fields and the corresponding stored carrot lots 2006–2008 allowed to identify the most important variables related to black spot losses. The concentration of DNA of R. carotae, as determined by Taqman qPCR assays, in the canopy or on root surfaces in carrot crops at harvest, did not correlate with black spot incidence in the corresponding carrot lots after storage. Thus, knowledge of the presence of the pathogen at harvest could not be used to predict risks of post-harvest losses. Umbelliferous plants were found in field margins of 84% of the fields surveyed. The disease incidence of carrot lots from such fields was 23% higher compared to carrots from fields where umbelliferous plants were absent. Increase of the variables ‘number of growth days’ and ‘mechanical damage on the carrot surface during harvest’ resulted in significantly higher black spot incidence after storage. A series of field and storage experiments confirmed the effect of these variables. Even if the total gross yield of carrots increased by harvesting late, the marketable carrots decreased on average from 66% to 6.6% after storage in a year of high infection. This drastic yield reduction was solely due to black spot disease caused by R. carotae. Future guidelines for Integrated Crop Management (ICM) of carrots produced for cold storage should recommend the reduction of the number of growth days in combination with harvesting under optimum conditions as sustainable measures to ensure marketable yields.