Fungus threat rises for food, wildlife

2012-04-12 08:19

Paris - Species of fungus, driven by trade, travel and climate change, pose a mounting threat to food supplies and biodiversity, scientists said on Wednesday.

Widely unknown to the general public, seven fungal epidemics are under way, striking bees, bats, frogs, soft corals and sea turtles as well as rice and wheat, they said.

Human health and livelihoods are at stake, for fungus costs $60bn a year in losses to corn (maize), wheat and rice alone, according to their assessment, published by the science journal Nature.

"In both animals and plants, an unprecedented number of fungal and fungal-like species have recently caused some of the most severe die-offs and extinctions ever witnessed in wild species, and are jeopardising food security," it warned.

The paper said a lethal skin fungus called Batrachochytrium dendrobatidis, discovered in 1997, has infected 500 species of frogs and toads in 54 countries, on all continents where amphibians are found.

Some areas of Central America have lost more than 40% of their amphibian species.

Bats in North America and Canada are being decimated by "white nose syndrome," a pathogen called Geomyces destructans, which causes a white fungal patch to grow on their muzzles. The fungus is believed to have a natural home in cave soil.

Species of the Microsporidia family of fungus are being blamed in part for for so-called colony collapse disorder among honeybees.

In tropical climates, the fungus Fusarium solani is causing eggs laid by the loggerhead turtle to fail to hatch, while a soft coral, the sea fan, is in decline, its immune system depressed by a soil fungus.

A pathogen called Magnaporthe oryzae, causing a disease called rice blast, has led to losses of 10-35% in the rice harvest in 85 countries.

Another fast-emerging concern for farmers is wheat rust, caused by Puccinia graminis. A strain called Ug99 can cause 100% crop loss, helped by farmers' over-dependence on a single wheat type.

Fungal destruction of these crops, and also of corn , potatoes and soybeans, currently amounts to 125 million tonnes a year, according to the study. Tackling this problem would be enough to feed one in 12 of the world's population.

Fungus is spread by tough, virulent and long-living spores that can be borne by wind or water.

But human intervention, through trade, transport and global warming, is accelerating its spread, the study said.

For instance, the amphibian fungus B dendrobatidis has gained a foothold in some ecoystems by the introduction of the North American bullfrog, which is resistant to the disease.

In the mid-19th century, a fungus called Phytophthora infestans triggered a catastrophic disease in potatoes known as late blight, causing millions of deaths from famine and an exodus to America.

The fungus originated in the Andes but hitched a ride in tubers to Mexico, and from there to the United States and finally to Ireland, according one theory.

"Crop losses due to fungal attack challenge food security and threaten biodiversity, yet we are woefully inadequate at controlling their emergence and proliferation," said Sarah Gurr, a professor of molecular plant pathology at Oxford University.

Addressing fungal epidemics starts at the bottom, with better understanding of how the pathogen interacts with hosts and the environment. In terms of action, "effective prevention and timely control" are best, as these stop an early outbreak in its tracks, according to the study.

Read more on:    science

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