Fungi – the good, the bad and the ugly

Fungi, plants, and animals live together in Tāne-mahuta, and all have important roles to play.

Fungi live with plant roots, helping the plant to get minerals and water from the soil. Fungi like hakeke or wood ear (Auricularia cornea) feed on dead wood, causing it to rot and return its nutrients to the soil. Insects and kererū feed on fungi, and fungi like āwheto (Ophiocordyceps robertsii) feed on insects. Some fungi such as pūtawa (Laetiporus portentosus) feed on living trees but without killing them. Our tūpuna had several uses for these and other fungi.

Food for kererū

Our ancestors will likely have seen the Cyttaria fungus in beech forest during spring while hunting kererū. The fungus grows on branches of living beech trees, causing the affected branch to become deformed and form odd-shaped lumps (called galls). On these galls during spring, the fungus forms lots of strawberry or golfball-shaped fruitbodies that produce spores for dispersal by wind. The fungus may also be spread by birds, as these ‘strawberries’ are a popular food for kererū. The Māori name for Cyttaria is not known. Maybe you could ask if any kaumātua know? In South America, related Cyttaria fungi are collected as a traditional food by Indian people.

Beyond Tāne-mahuta, fungi are also important in our homes and our hospitals as well as in farms, orchards and gardens. For example, at home, we use yeast (tiny fungi of just one cell each) to make bread rise, and we can see that our food is too old when mould fungi (puruhekaheka) start to grow on it.

For eating, several different kinds of edible mushrooms are grown in mushroom farms and sold as food, or sometimes edible field mushrooms can be collected in a farmer’s field. Marmite, made from yeast, is a popular spread on bread. If you become sick, a doctor may give you a fungal medicine called an antibiotic. Antibiotics were first discovered from fungi. Just like us, fungi need to keep bacteria away, so we’ve used chemicals invented by fungi for our medicine against bacteria.

Penicillin

In 1928, Alexander Fleming discovered a bread mould had contaminated a bacterial plate he was studying. His observation that the fungi had killed the bacteria that surrounded it led to the discovery of penicillin. “When I woke up just after dawn on September 28, 1928, I certainly didn’t plan to revolutionise all medicine by discovering the world’s first antibiotic, or bacteria killer,” Fleming would write later, “but I guess that was exactly what I did.” It took over 10 years of research by many teams of scientists to produce penicillin in a stable form and to mass produce it, but when they did, it was soon hailed as a miracle cure.

Penicillin is a natural antibiotic produced by the fungus to prevent bacteria from invading it. Since this discovery, several antibiotics have been discovered from different fungi, and with the increase of antimicrobial resistance, scientists continue to look to different fungi for new antibiotics.

Some fungi that we don’t want

There are also fungi in Aotearoa that we would rather not have. These may have come here with tūpuna and early Pākehā or as hitch-hikers on plants or in soil from other countries. Like plant weeds and animal pests, there are also fungi that can be weeds and pests. At our airports and seaports, care is needed to avoid bringing in any unwanted fungi that are new to Aotearoa. No fruit (that may contain fungi and insects) is allowed in our plane bags, and no soil on our shoes and tent pegs. As tangata whenua, biosecurity at our ports is important for our mātua and tamariki and to also protect Tāne-mahuta.

Fungal pests include those that cause diseases of our food plants. Kūmara and taewa, for example, can be damaged by disease-causing fungi in the soil. These fungi feed on the kūmara or taewa, causing them to rot. Sometimes, in fields with soil containing these fungi, farmers may need to stop growing kūmara and taewa and change to other kinds of plants that can grow without being attacked by these fungi.

In Tāne-mahuta, harore or the honey mushroom (Armillaria novae-zelandiae) is not considered a seriously damaging parasite, but for some introduced crop plants, harore has been recorded as a disease-causing fungus. It can infect and kill pine tree seedlings when they are planted on land formerly covered by native forest. Harore also killed some early plantings of kiwifruit by attacking kiwifruit roots that grew close to infected roots of shelterbelt trees. Spores of harore first infected the exposed stumps of felled shelterbelt trees and then grew out through the dead roots to contact the living kiwifruit roots.

Other plant diseases caused by fungi include Dutch Elm disease (elms), brown rot (peaches) and powdery mildew (grapes). Myrtle rust, a fungus that arrived in New Zealand on strong winds from Australia in 2017, is particularly worrying as it infects many trees from the myrtle family, including our beautiful pōhutukawa.

Some fungi are also responsible for human diseases and can infect us – like thrush, athlete’s foot and ringworm.

Why does wood rot?

When branches fall or a tree dies, the dead wood on the ground is soon alive with other life. Many different kinds of fungi start feeding on the wood. They may arrive as spores in the air or grow up from the soil below, or they may already be in the tree before it dies. As the fungi feed on the cells of the wood, the wood starts to become softer. We describe this softening as rot. Insects can also begin to feed on the softened wood and on the fungi. This rotting log may continue to be full of life for many years until eventually there’s no food left for the fungi, and what little remains of the wood becomes part of the floor and soil of Tāne-mahuta, from which new plants feed and grow.

Tēnei taku waka te waiho hei poupou harore.
This is my canoe left as a post of fungus.

This whakataukī refers to the role of fungi in wood decay (Brougham & Reed 1987).

Where do the fallen leaves go?

Just like wood, fungi and insects feed on fallen leaves. The leaves rot as a result and finally become part of the soil, returning nutrients once in the tree back to the soil. The fungi are thus the great recyclers of Tāne-mahuta.