Many types of fungi live on trees. While most are harmless and beneficial, certain types can pose risks to human health through various exposure routes.
Diverse Nature of Tree Fungi
Tree fungi represent a vast and diverse group of organisms, ranging from microscopic molds to visible mushrooms and bracket fungi. They are an essential component of forest ecosystems, primarily functioning as decomposers that break down dead wood and return nutrients to the soil. This process maintains forest health and nutrient cycling.
Fungi can also form symbiotic relationships with trees, where both organisms benefit. Mycorrhizal fungi, for instance, associate with tree roots, helping the tree absorb water and nutrients while receiving sugars from the tree. The visible parts of these fungi, such as mushrooms or conks, are fruiting bodies that release spores. The main fungal body, called mycelium, remains hidden within the wood or soil.
Specific Health Concerns
Certain tree fungi can lead to health concerns in humans, primarily through allergic reactions, skin irritation, and, in rare instances, infections or toxicity from ingestion. These issues often arise from exposure to airborne spores or direct contact.
Airborne spores released by some tree fungi can act as allergens, triggering respiratory issues in sensitive individuals. Just like pollen from trees, fungal spores can cause symptoms such as sneezing, coughing, nasal congestion, and itchy eyes or throat. For individuals with asthma, inhaling these spores can exacerbate their condition, leading to wheezing and shortness of breath.
Direct contact with certain fungi or fungal spores can result in skin irritation or dermatitis. This can manifest as rashes or itchy skin, especially if the skin has cuts or abrasions. For example, a fungal infection called sporotrichosis is caused by the Sporothrix fungus found in soil and on plants. It can enter the skin through small cuts or pricks from thorns or plant matter, leading to skin lesions.
While uncommon, some fungi associated with trees can cause opportunistic infections, particularly in individuals with weakened immune systems. Cryptococcus neoformans is an environmental fungus that has been isolated from decaying wood in tree hollows and various tree species, though it is also widely found in soil and bird droppings. Inhalation of its spores can lead to respiratory and neurological diseases in susceptible individuals.
Ingesting poisonous fungi that grow on trees or in their vicinity poses a significant risk. Some mushrooms found on trees, like the Jack O’Lantern mushroom, can cause severe gastrointestinal symptoms if consumed. Other highly toxic species, such as the Deadly Galerina or the Death Cap, can be found growing on or near trees and can cause liver failure and even death if ingested. Proper identification is crucial, as some poisonous varieties can resemble edible ones.
Identifying Potentially Harmful Fungi
Recognizing the signs of potentially harmful fungi on trees involves observing specific visual cues. Fungi can appear in various forms, not always as classic mushroom caps.
Signs of fungal presence include shelf-like growths (conks or bracket fungi) on trunks or limbs, powdery or sooty films on leaves, or cankers and oozing lesions on bark. Discoloration, wilting, premature leaf drop, or dark spots on leaves can also indicate a fungal issue with the tree itself. While these signs often point to a tree disease, some may also signal fungi that pose a risk through human contact or airborne spores.
Fungi growing in areas of frequent human activity, such as parks or residential yards, might be more concerning due to increased chances of accidental contact or spore inhalation. Avoid touching unknown fungi, especially those with bright colors, unusual shapes, or powdery substances, as these characteristics can sometimes indicate toxicity.
Safety Precautions and Professional Guidance
To minimize potential risks from tree fungi, adopt certain safety measures. Avoid direct contact with unknown fungi by avoiding touching, inhaling spores, or ingesting them. If handling is necessary, such as during yard work involving decaying wood or fungi, wearing gloves and a mask can help reduce exposure to spores and prevent skin irritation.
Ensuring good ventilation in areas where fungi might be present, especially if they are indoors or in enclosed outdoor spaces, can help disperse airborne spores. If you suspect exposure to harmful fungi and experience symptoms like a persistent cough, rash, or other unusual health changes, consulting a healthcare professional is recommended.
For concerns about fungi growing on trees, it is best to seek professional guidance. Arborists or mycologists can identify fungal species and assess the health of the tree. They can advise on whether removal or other management strategies are necessary to ensure the safety of both the tree and people.