They don’t want to say “we don’t know,” but they don’t know. At least they have a working hypothesis about the collapse of the 2017 peanut crop in much of Florida: it has to do with variations in rainfall.

Bob Kemerait, Southeast Farm Press, 22 January 2018, Peanut collapse: Something happened but it’s not clear exactly why,

…For months, University of Florida’s Institute of Food and Agricultural Sciences Extension agents led by Anthony Drew, Mace Bauer and Dee Broughton had been sounding the alarm that an unprecedented collapse of the peanut crop was occurring across large areas of Florida’s production region. Symptoms of this collapse included stunted plants, late-season yellowing and leaves with distinctive marginal leaf necrosis. Where most severe, entire fields wilted in the weeks prior to harvest. Abysmal yields, off by as much as 45 percent, forced some to consider their future in farming if solution could not be found.

During the latter third of the season, these Extension agents with support from specialists like Dr. Nick Dufault and Dr. David Wright and peanut breeder Dr. Barry Tillman spent hours on the telephone, sending e-mails, texting and sharing photographs with anyone who might help them diagnose the problem. The condition was most acute in the sandy soils west of Gainesville, but stretched from Columbia County to Marianna in Jackson County.

That would include parts of the Suwannee River Basin.

Reports from symptomatic plant samples sent to disease diagnostic labs did not explain the underlying cause. Pictures were shared with crop experts in neighboring states and explanations were as confident as they were varied. For many, the distinctive necrosis plainly evident along the leaf margins was evidence of a deficiency in potassium. For others, the stunted or wilted plants strongly suggested drought, damage associated with root-knot nematodes or low soil pH. The late-season symptoms convinced some others that the issue had to be related to tomato spotted wilt and, perhaps, Diplodia collar rot. As the onset of some symptoms followed the passage of Hurricane Irma, others wondered if salty water from the Gulf of Mexico had been dumped on the fields in the path of the storm.

The article continues, “puzzling and inconclusive,” and “overarching cause of the decline remained unknown.”

In December, peanut specialists from the University of Florida, Mississippi State, Auburn University, the University of Georgia and Clemson University met to listen to Extension agents Anthony Drew, Mace Bauer and Dee Broughton and to discuss the peanut decline in Florida. Specialists reported that some of the symptoms, for example marginal leaf burns, were also observed in southern Georgia, but nowhere was the impact remotely as severe as it was in Florida.

…there was unanimous agreement that something very serious had occurred. Second, it was generally agreed that the cause was not some new disease or pest, but likely the result of a number of factors interacting at the same time.

A partial explanation was that abundant rainfall and overcast days early in the season affected the development of roots and may have leached nutrients, especially in deep sands. Shallow root systems would have been more affected by late-season heat and drought stress, less able to recover from damage from diseases and nematodes, and less successful at scavenging for nutrients. Saturated soils during the season could have affected normal root functions and nitrogen production by Rhizobium nodules.

The story says that’s at least a testable hypothesis.

Perhaps if growers grew more varieties of peanuts, or not so many acres of them and instead interspersed them with more crop varieties, maybe even with less use of pesticides, the peanut crop wouldn’t be susceptible to such a widespread simultaneous failure. Oh, wait, that’s pretty much what the multi-state group recommended, except they didn’t mention less pesticiding:

The most unanimous recommendation from the multi-state meeting was as follows: Though we cannot explain what happened in 2017, growers in 2018 should implement as many best management practices as they can to include, rotation, tillage, fertility management, timely irrigation and pest control.

However, “rotation” includes not always growing the same crop, “fertility management” could include using multiple crop varieties, “timely irrigation” could mean less irrigation and thus less withdrawal of water from the Floridan Aquifer, and “tillage” could include using a cultivator, which is a form of pest control without pesticides.

Thanks to WWALS Science Committee Chair Tom Potter for spotting this story.

 -jsq, John S. Quarterman, Suwannee RIVERKEEPER®

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