Aflatoxins are naturally occurring, carcinogenic substances produced by the same fungus, Aspergillus flavus, which helped cause peanut growers much frustration and stand loss early in the 2020 season. But aflatoxin is a much larger and more difficult problem than stand loss. When found in even very small quantities, aflatoxin makes peanuts unsuitable for anything other than crushing for oil.
Aflatoxin is most severe when peanuts (and field corn) are grown under hot and dry conditions, especially later in the season, and when moisture is not adequately managed when peanuts are in storage. Aflatoxin is an increased threat to peanuts grown without irrigation and those grown in the dry corners of an irrigated field. There are several other factors that increase risk to aflatoxin, to include mechanical and insect damage to the pods, timing of harvest and rainfall at harvest.
As an Extension specialist and plant pathologist, I generally worry about fighting “bad guys” like Aspergillus crown rot, tomato spotted wilt, white mold, and leaf spot diseases during the growing season. What happens after the peanuts are picked has been largely off my radar.
However, the urgency of post-harvest concerns is now front and center as they threaten not simply a field, or 1,000 fields, but an entire industry. For some growers, once peanuts are inspected and accepted at the buying point, they consider them “someone else’s problem now." We must change that belief.
I’ve said proudly many times that the best peanuts in the world are grown in Georgia and in the Southeastern United States. It’s easy to say this because I believe it’s true, many others believe it’s true, and no one has ever challenged me on it. No one, that is, until now.
In a recent meeting with leadership from Premium Peanut in Douglas, Ga., Dr. Cristiane Pilon and I received a similar message. “Yes, of course, outstanding peanuts are grown here in Georgia. But we are fooling ourselves, hurting ourselves, if we believe that our peanuts are necessarily better than those grown elsewhere. Argentina has largely taken our peanut market in Europe. China has begun to challenge our market in Japan. We are at a crossroads. If we cannot protect quality, then we will lose the export battles. One of the biggest threats to our exports, and perhaps to the future of our industry, is aflatoxin.”
Though early in 2021, there are several important reasons why NOW is precisely the time to talk about aflatoxin. First, the good news. Because conditions at harvest in 2020 were generally favorable, growers can expect fewer problems with seed and Aspergillus flavus than they experienced in 2020. This does NOT mean seed treatments and in-furrow fungicides won’t be important, only that there should be less risk to stand loss unless hot and dry conditions coincide with planting which predisposes the crop to Aspergillus crown rot and lesser corn stalk borers.
There is also the “other” news. First, peanut growers must understand that aflatoxin is a major threat to the American peanut industry. While you may feel safe once your peanuts have been accepted at the buying point, any threat to our peanut industry is a direct threat to our growers. We have significant competition in the world, especially from Argentina, where aflatoxin is uncommon, and from China.
Argentinian peanuts are popular in Europe because they can consistently meet low aflatoxin demands that are more challenging for American peanuts. (I don’t know about you, but I don’t want to be second best to Argentina, China, or anyone else.) Next, growers can help the entire industry by using in-season management strategies to reduce threat to aflatoxin. These include timely irrigations and appropriate insect management. Lastly, at harvest, growers must ensure that peanuts are segregated based upon irrigated/non-irrigated. Trying to get a load passed Seg 1 may be beneficial in the short run, but if Seg 1 turns into Seg 3 while in storage, everyone loses in the end.
Growers should not feel like the “Lone Ranger” in the battle against Aspergillus flavus and aflatoxin. An Aflatoxin Task Force has been organized by leaders in the peanut industry and the team includes members from land-grant universities, the USDA-ARS, and our peanut commodity commissions, among others. Research projects are planned and some are underway. For example, research at the University of Georgia will assess the impact of irrigation optimization on aflatoxin. Research will also address Aspergillus flavus and seedling disease management.
Management of aflatoxin is a complex issue that involves a lot of moving parts. Research will offer solutions to at least some of the problems. However, triumph over aflatoxin and the impact on the future of our industry is impossible without growers buying into the efforts needed for success.