Global Warming, Droughts, Helping to Spread Toxic Fungus in Corn Crops

Aspergillus flavus moldIn 2011, the toxic, yellow-green or green-black mold aspergillus (Aspergillus flavus) was found to have contaminated about 8% of the corn crop coming from the State of Missouri (source: Grain Inspection Service). Last year, more than half of that state’s corn crop was contaminated, rendering large quantities of one of our nation’s biggest food crops unfit for consumption.

This increase is largely attributed to persistent drought conditions in the “bread basket” Midwestern states. While many molds and fungi prefer warm but moist conditions, A. flavus had evolved to thrive under hot and dry climate conditions.

A. flavus  disperses spores containing  flavatoxin — an toxic, organic compound that has long poisoned cattle and killed pets — which can be fatal if ingested, and even when not lethal, produces severe symptoms such as jaundice, internal bleeding and even liver cancer.

Federal law stipulates that crops that contain more than 20 parts per billion of the mold-type fungus are not permitted to cross state lines. The tiny amount is equivalent to about “100 (infected) corn kernels in a truckload of corn”, according to Ronnie Heiniger, professor of cropping systems at North Carolina State [source: see link below], and indicates the high toxicity of this fungal poison.

“We have a big aflatoxin problem. There are loads of corn coming to the [grain] elevators that have been rejected, ” stated Charles Woloshuk, a botanist and plant pathologist at Purdue University [source, see link below]

Corn production by county in the United States, 2010 (USDA)

Annually, the US agricultural industry suffers $190 million in crop losses, due to the fungus that infects many other crops such as oilseed, spices, tree nuts, groundnuts, milk, meat and dried fruit. The dollar amount of annual crop losses is sure to rise as indications are that the drought conditions experienced in over half the land mass of  the US ( over the past 2-3 years) will continue.

Flavatoxin Contamination in the Developing World

The aforementioned crops are major staple foods for billions of people around the globe.

Internationally, there are strict regulations in placed to control what are considered to be acceptable levels of the toxin in our food. Even still,  poisoning by aspergillus toxin — termed aflatoxicosis — is quite common, world wide. What is more worrisome to many is that any given load of corn could be over the maximum limit (for the toxin), and so farmers are permitted to “dilute” the contaminated corn with safe corn to bring the load under the permitted toxin limit. Given the imprecision of this activity, it is not surprising that crop loads with higher levels of contamination occasionally slip through the system.

Aflatoxin poisoning is felt most drastically in developing countries where a general lack of education amongst subsistence farmers concerning the mold’s presence contributes to the prevalence of flavotoxicosis. Due to additional issues such as a lack of resources, infrastructure and technology, many of these nations are not able to establish an adequate grain testing system.  Not being able to test crops for contamination, developing world farmers don’t know whether they and their families are consuming poisoned crops.

For these reasons, aflatoxin contamination is considered a global food security issue.

Spread by Global Warming?

While human-caused global warming does not “cause” aspergillus/flavatoxin contamination, it does promote the conditions (hot,dry, drought) under which the mold can spread to wider regions, thus impacting larger number of crops, and people.

In the coming years, we should expect to hear more about the spread of toxic microbes, fungi, pests and/or diseases — previously limited in range or severity — as the climate continues to become more variable and extreme in its seasonal fluctuations.

Also: we will most likely hear of the impact from food contamination combined with the impact from loss of agricultural land due to degraded soil; this will surely add to global food security concerns in the coming years.

Some source material for this post came form the Sci Am article ‘Fortified by Global Warming, Deadly Fungus Poisons Corn Crops, Causes Cancer’ By Mollie Bloudoff-Indelicato

More about Aspergillus flavus (from wikipedia):

A. flavus is found globally as a saphrophyte in soils and causes disease on many important agriculture crops. Common hosts of the pathogen are cereal grains and legumes. Specifically, A. flavus infection causes ear rot in corn and yellow mold in peanuts either before or after harvest. Infection can be present in the field, pre-harvest, post-harvest, during storage, and during transit. It is common for the pathogen to originate while host crops are still in the field; however, symptoms and signs of the pathogen are often unseen. A. flavus has the potential to infect seedlings by sporulation on injured seeds. In grains, the pathogen can invaded seed embryos and cause infection, which decreases germination and can lead to infected seeds planted in the field.

Top Photo: (microscopic image of A. flavus); CDC




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