Growers in Texas faced the unusual challenge of fumonisin in their corn crop this past fall. Wetter than normal weather at the right stage of the corn’s development led to high amounts of this mycotoxin popping up in truckloads all over the Panhandle, causing headaches for farmers, feeders and grain handlers. Testing uncovered the situation at the beginning of the corn harvest and many farmers had several loads of corn turned away at delivery points because fumonisin levels were too high.
At a meeting hosted by the Texas Corn Producers recently in Dumas, Texas, Texas AgriLife Extension Agronomist Jourdan Bell, along with other speakers, talked to producers about the lessons that they can take away from this highly unusual situation in order to better prepare themselves in case the situation should arise again.
Bell said it’s important to understand that fumoninsin is a mycotoxin produced by the fusarium fungi, fusarium verticilloides. Fumonisin is particularly toxic to many species of livestock and humans, which is why there are regulations to test for it among other mycotoxins. While the danger can be mitigated somewhat through blending, it’s still an animal and human health situation farmers must take seriously.
Weather is the deciding factor
The first takeaway from this recent outbreak is that the right weather conditions have to exist for the fungus to take hold in the corn plant, Bell told growers. This year caught everyone off guard. And it all traces back to the weather patterns in the season.
“Hot and dry conditions at flowering, followed by rain and high humidity will favor fungal growth,” she explained. In 2017, early corn planted in May saw a hot and dry June and July at flowering. This opened a door for fusarium verticilloides, which is naturally present everywhere, to infect the developing kernel. Then an unusually wet, cool and humid August and September was the perfect nursery for the fusarium verticilloides to grow and then release the fumonisin into the ear at grain fill.
“The fusarium fungus needs the correct moisture and amylopectin, or starch, to form fumonisin,” Bell said. “Extended periods of heavy precipitation and high relative humidity during grain fill, along with temperatures ranging from 50 to 86 degrees, are ideal for fumonisin formation.” That just isn’t normal for the Panhandle in August, where daytime temperatures usually range from the 90s to over the 100-degree mark.
Weather forecasts predict a return to normal hot and dry conditions this summer, with slightly below average precipitation, Bell told growers. That’s bad for growing corn, but in theory it’s good for stopping fumonisin from developing in this coming season.
Some hybrids may offer tolerance
The very nature of fumonisin infections means it is difficult for researchers like Bell to create trials targeted at the mycotoxin. Because the weather pattern is unusual, what research Texas AgriLife has conducted has occurred in plots that were by chance in the middle of fumonisin outbreaks. And yet, in the 2017 field trials Bell said two hybrids showed consistently lower levels of fumonisin compared to their trial mates. They happened to have the Bt trait VIP3a. This trait, she explained, gives corn a high tolerance to head and common smut. Which leads us to the next takeaway from the outbreak, giving corn a healthy head start can mitigate mycotoxins like fumonisin.
“In many areas, we had lots of smut in 2017,” Bell explained. “Smut acts like a sponge for all the pathogens in that field, so you need a hybrid with high tolerance to both head and common smut.” Bell also advised growers to look for hybrids that have tight husks around ears, and ears that don’t grow upright. While many may select more open-husk corn hybrids to facilitate dry-down in the field at harvest, those same traits can allow water to get in close to the ear, promoting mold and creating the perfect place for fungi to grow.
Healthy corn that isn’t stressed by drought or too high of a population doesn’t give smut an opportunity to flourish, she added. So growers who are really concerned need to manage for optimum plant health when possible.
The unusual nature of this fumonisin outbreak led to many myths and Bell dispelled these. For example, some growers thought that controlling corn thrips could be the key to stopping the disease. She said there is some data from California that suggest thrips might challenge the plant’s health enough to open the door to the fungus, but it’s not for certain. Plus, a grower could spray for corn thrips and then see a bloom of mites that flares up even worse in the field, she said.
Some growers thought plowing a field could contain the fumonisin, but Bell cautioned that the fusarium fungus that causes fumonisin is naturally occurring in all soils, and data shows no significant difference in tilled versus no-tilled fields.
“Besides, we want to maintain that residue because it has so many benefits for our fields,” Bell said.
For now, choosing the right hybrid with a trait to control smut, or treating seed with a fungicide, she explained, are the only tools a grower has if he’s really concerned fumonisin might flare up in his fields again. Managing your corn field to reduce plant stress not only gives you better yields, but also healthier plants that can better withstand the fusarium fungi that lead to fumonisin, she added.
Testing at the speed of commerce
The fumonisin outbreak brought to light another issue regarding licensing and fees for farms who ship directly to end users. Gibson’s staff fielded many phone calls from concerned farmers who’d sold their corn directly to feed yards and received letters from the Office of the Texas State Chemist. The letters told those farmers they were subject to licensing regulations and fees when they sell a feed source into the livestock chain.
Gibson explained that farmers who were shipping corn from the field to the local co-op were covered by the co-op’s license. The co-op is then responsible for testing and verifying that what corn is shipped to the feed yard or end user is less than 60 parts per million, or in the case of a dairy less than 30 parts per million.
However, farmers who ship from the farm to the feed yard or another end user are their own distributors. In the worst case scenario, they might have slipped by this year, but if a farm truck is spot checked at the feed yard next fall and the fees haven’t been paid, they can seize the truck until they are paid.
Interestingly, Gibson noted, corn shipped by rail from the Corn Belt into Texas, which also may have fumonisin or other mycotoxins, wasn’t necessarily tested for fumonisin this last year. Unless the company receiving the corn asked for the test, it wasn’t likely done. That is something Texas Corn plans to bring up at the national level.
Texas feeders and dairies operate under strict U.S. Food and Drug Administration guidelines, said Ben Weinheimer, vice president of the Texas Cattle Feeders Association, Amarillo, Texas. And yet, because fumonisin is difficult to replicate in a field test setting, it also means it’s difficult to source enough fumonisin corn to replicate feeding trials to really get a handle on how much is acceptable in beef and dairy rations or how feeders can mitigate the risk if fumonisin pops up again.
It’s especially important to have better testing procedures in place at the feed yard so that harvest isn’t held up at the scales.
“We need to have a system that can run at the speed of commerce,” Weinheimer said. “Feed yards varied on their protocols to either accept or reject corn.” It’s his hope that this past fall leads to discussions between feed yards and farmers. Especially as contracts for 2018 corn are now being negotiated.
If the 2017 fumonisin outbreak taught any lesson, it’s that communication among farmers, Extension personnel, customers and farmer organizations is key to weathering any “perfect storm” that may hit farm country.
Jennifer M. Latzke can be reached at 620-227-1807 or [email protected].
