Botrytis cinerea, commonly known as Grey Mold, is a necrotrophic fungus frequently seen on produce like strawberries and grapes. It is a highly destructive plant pathogen that causes significant economic damage by spoiling crops both before and after harvest. While the fungus is not typically considered a human pathogen that causes infection, the primary health concern lies in the inhalation of its airborne spores and, to a lesser extent, the ingestion of contaminated food.
What Botrytis Is and Where It Thrives
Botrytis cinerea is a ubiquitous fungus with a broad host range, affecting over 200 species of plants, including fruits, vegetables, and flowers. It thrives in environments characterized by cool temperatures and high humidity, such as greenhouses, vineyards, and storage facilities.
The fungus survives by producing sclerotia, which are resistant survival structures, or as mycelia in old plant debris. When conditions are favorable, these structures germinate to release asexual spores (conidia) that are easily dispersed by wind and water. This widespread presence means human exposure to its spores is common in agricultural settings.
Respiratory and Allergic Reactions to Spores
The most significant health risk posed by Botrytis cinerea comes from inhaling its microscopic spores. Although the fungus is not infectious to people, its spores contain potent allergens that can trigger allergic and respiratory issues. Airborne spores are found in high concentrations in environments like greenhouses and vineyards where the fungus is actively growing.
Exposure is a recognized cause of allergic rhinitis, involving symptoms like sneezing, nasal congestion, and itchy eyes. For individuals with pre-existing conditions like asthma, inhaling the allergens can exacerbate symptoms, leading to wheezing and difficulty breathing. B. cinerea is considered a prevalent allergen, sometimes ranking among the most common molds to which people show sensitization.
A more severe, though less common, condition associated with prolonged, high-level occupational exposure is hypersensitivity pneumonitis, sometimes called “Wine-growers’ lung.” This serious allergic reaction in the lung’s alveoli can lead to inflammation and chronic lung disease over time. Agricultural workers, such as those in the viticulture or horticulture industries, are at the highest risk for developing these severe respiratory reactions.
Risks Associated with Ingesting Contaminated Food
Concerns about ingesting food contaminated with Grey Mold are widespread. Botrytis cinerea is generally considered low-risk when ingested because it is not known to produce mycotoxins severely toxic to humans, unlike molds such as Aspergillus or Penicillium. The fungus produces toxins like botrydial and botcinic acid primarily to kill plant cells, but these compounds do not have a documented significant effect on human health.
The human digestive system is generally effective at neutralizing small amounts of mold consumed accidentally. While a person with a severe mold allergy might experience a minor reaction, the primary danger is not systemic poisoning. Food safety experts recommend discarding any food showing visible signs of Grey Mold, especially soft, porous items like fruits. This is advised because the mold indicates spoilage and the presence of other potential bacteria or fungi. Since the mold penetrates deeply into soft produce, cutting off the visible surface mold does not guarantee the rest of the food is free of contamination.
Reducing Exposure and Controlling Contamination
The most effective way for the general public to reduce exposure to Botrytis is through careful food handling and environmental control. In the kitchen, proper refrigeration and prompt consumption of fresh produce will limit the time Grey Mold has to develop post-harvest. Washing produce before eating can help remove spores present on the surface, but it cannot remove the fungus once it has penetrated the plant tissue.
For agricultural workers or avid gardeners with high environmental exposure, taking precautions to minimize spore inhalation is advisable. This includes ensuring good air circulation in greenhouses and other enclosed growing spaces, as the fungus thrives in stagnant, humid air. When handling heavily infected plant material, wearing a particulate filtering mask can significantly reduce the number of airborne spores inhaled, thereby lowering the risk of developing allergic or asthmatic reactions. Maintaining low humidity levels indoors, especially in basements or storage areas, also helps to prevent the growth of all types of mold, including Botrytis.