Adjusting Rapid Mycotoxin Detection Strategies to a Changing Climate

The impacts of climate change are making themselves known in many ways: destructive storms such as hurricanes, flooding, extreme heat and drought all affect agricultural products and the animals and people who rely on them. As the FDA notes in a summary of the effects of hurricanes and flooding on the safety of animal food crops, extreme weather phenomena such as flooding damage grains and other agricultural products, giving mycotoxin-producing molds such as Aspergillus and Fusarium strains an opportunity to infect them¹. Indeed, the 2017 BIOMIN Mycotoxin Survey indicated a worldwide increase in levels of fumonisin, a mycotoxin produced by Fusarium²; many speculate that warmer, wetter weather is leading to this increase³. 

This makes on-site mycotoxin analysis an important tool that provides producers with rapid results that give them a chance to respond to volatile weather conditions. In this article, we demonstrate this with two examples from the United States: a case study on a tactical response to increased fumonisin levels in corn in the southern Great Plains as a result of hurricane-induced flooding in 2017, and a review of common practice from peanut producers confronted with higher aflatoxin levels caused by drought in the southeastern United States.

Case study: adjusting detection ranges in strip tests to deal with extreme levels of fumonisin

Farmers in several food-producing regions in the world are confronted with flooding more frequently than in the past. In March of 2019, Iowa, Nebraska, Missouri and Kansas experienced historic flooding as a result of ice jams, the melting of a record snowfall and excessive rains. This led to the failure of at least 30 levees, the flooding from which affected approximately 90,000 grain bins and more than 16 million acres of corn, soybean and wheat. The total economic damage exceeded $7 billion⁴.

These floods represent the continuation of a trend. Instances of flooding and accompanying agricultural damage continue to dominate headlines in the United States.

After Hurricane Harvey made its initial landfall on August 25, 2017 as a Category 4 storm, it continued to move further inland, dumping heavy amounts of rain in its path. During this time, annual harvest was fast approaching; no one could have predicted the catastrophic agricultural events that would soon follow, specifically in the Texas and Oklahoma Panhandles, Southwestern Kansas and areas of Southeastern Colorado.

In September 2017, as the harvest season began, corn samples were collected and sent to third-party laboratories for analysis. Signs of high fumonisin levels were prevalent in the Texas Panhandle due to the excessive rains from Hurricane Harvey, which occurred just prior to the harvest season. The rains provided Fusarium molds, which produce fumonisin, with ideal growing conditions. Although not widespread and showing variation from county to county, corn samples were seen at unprecedented fumonisin levels, such as 30 ppm, 50 ppm, 70 ppm and even 100 ppm.

Depending on the intended product usage, acceptable fumonisin levels can widely range in the United States from 2 ppm to 4 ppm for human consumption, and in animal feeds (corn and corn by-products) from 5 ppm to 100 ppm. However, in Europe, the levels can be even stricter, ranging from 0.2 ppm to 4 ppm for human consumption and 5 to 60 ppm in animal feed⁵. As the fumonisin concern escalated, mycotoxin testing continued to be a primary discussion amongst those in the industry, and in the Texas Panhandle in particular, where fumonisin concentrations usually average around 4 ppm. Amid growing concern, and after much deliberation over a standardized number, cattle feeders designated 60 ppm as a safe level for their livestock.

From the beginning of this crisis, Romer Labs was involved. Romer Labs representatives received several requests regarding the ability to test on-site for high fumonisin levels in incoming corn shipments. At the time, the AgraStrip® WATEX® Fumonisin test kit offered ranges between 0-5 ppm and, with a dilution step, 5-30 ppm. Cattle feeders indicated an immediate need to test at much higher fumonisin levels than the kit initially could run due to the increased fumonisin occurrence in corn grain. Romer Labs responded by successfully developing a third curve using yet another additional dilution step, giving the AgraStrip® WATEX® Fumonisin kit an additional range of 30-100 ppm. 

The process to complete the third curve was finalized within a matter of days and ready to be deployed in the field. Due to the high levels seen at the beginning of the harvest season, cattle feeders chose to start testing only at the 30-100 ppm level. This continued into 2018.
On its face, this example shows an increased need for mycotoxin testing in the wake of an extreme weather event, such as flooding caused by a hurricane or tropical storm. Yet the capabilities of testing techniques must also be commensurate to the new and unusual challenges that accompany extreme weather. In this case, the quantitation range needed to be expanded to meet exploding fumonisin concentrations. Flexibility on the part of test kit providers and those who apply them in the field will grow more necessary. 

Using test kits to monitor extreme levels of total aflatoxin in peanuts

Flooding is, of course, not the only extreme weather phenomenon that can lead to higher levels of mycotoxins. Few know this better than peanut farmers in the southeastern US, where drought and heat can put crops under considerable stress, rendering them vulnerable to aflatoxin-producing strains of Aspergillus.

Aspergillusparasiticus and Aspergillus flavus are chiefly responsible for aflatoxin occurrence in peanuts. These molds occur naturally in soil, making it difficult to prevent their coming into contact with the legumes, which grow underground. When average temperatures remain at or above 32°C (90°F), and when these hot conditions converge with drought, the peanuts become even more susceptible to aflatoxin occurrence. These represent pre-harvest stressors, over which farmers have very little control. 

Weather conditions around harvest time can exacerbate the stress the peanuts experience and lead to shell damage, giving Aspergillus more opportunity to invade. If intense periods of rain or flooding occur just before or during harvest, the peanuts may not have enough time to dry sufficiently before being put into storage. As is the case with several molds, humidity in excess of 14% can favor the growth of mycotoxin-producing molds in storage facilities.
So what to do if you suspect or discover that drought and heat have resulted in high levels of aflatoxin in a crop? Usually, it is the responsibility of the buying points or the shellers to take action. First, operators of peanut buying points grade the peanuts according to several characteristics defined by the USDA-FSIS: quality of shell, visual presence of mold, loose shell kernels, etc. Peanut quantities evaluated as “Seg 1”, that is, with the best FSIS rating, are then tested with strip tests, which serve further to segregate the peanuts. Buying points then decide how to store them according to aflatoxin concentration. 

By isolating the highly contaminated peanuts, buying points preserve the integrity of uncontaminated or less contaminated peanuts so that these remain suitable for direct human consumption. The highly contaminated peanuts are often destined for products whose production eliminates or reduces aflatoxin content. For example, aflatoxins tend to transfer from the intact legume to oil at low rates. Refining and other treatment further reduce aflatoxin levels. 

From the storage warehouse, peanuts are then transported to shelling plants, where strip tests provide information about aflatoxin concentration, guiding decisions about further usage, such as the type of food into which they can be integrated. Peanut shells intended for animal feed are tested once again for aflatoxins before making their way to feed mills.  

Conclusion: Changing climate, changing test methods

Though many of these methods are common practice for producers of peanuts, extreme drought and heat combined with untimely occurrences of heavy rain have caused higher than average aflatoxin levels in peanuts. As the climate changes and the earth warms, extreme weather will continue to complicate efforts to keep mycotoxins and the molds that produce them at bay. Drastic events such as hurricanes are unpredictable, requiring quick adaptability on the part of farmer and grain traders to adjust to heightened levels of fumonisins and other mycotoxins that thrive in wet, hot conditions. 

Such new environmental conditions may necessitate creative approaches that go beyond simply adjusting the parameters of existing test kits to maintain food and feed safety. Just what such solutions entail is the focus of much research and speculation going forward.