At a recent meeting, Extension specialists from across the Southeast were able to agree that something went wrong in Florida’s peanut fields last season. However, determining the cause of the problem has been anything but straightforward.
Sometimes, not very often, but sometimes I want to shrug my shoulders and say I just don’t know what happened. Helping growers understand what went wrong with a crop and working to develop solutions are two of the most rewarding things we do in Extension. But they can also be the most difficult.
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.
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.
As concern for the impact of the situation on peanut farmers increased, efforts were made to document the extent of the problem and to collect samples for analysis. It was estimated that 25,000 acres of the peanuts grown in peninsular Florida east of Tallahassee were affected. Soil samples and plant samples from the region were submitted for nutrient, nematode and disease testing. The results were puzzling and inconclusive.
Though the symptoms seemed easily associated with well-documented maladies, test results did not point to any cause that would explain crop decline. Nematodes, diseases and tomato spotted wilt could not be consistently associated with affected areas nor could potassium or any other soil nutrient issues. After significant effort, the 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.
The group carefully listened and then discussed possible scenarios to explain what had happened, reaching several conclusions in the process. Though the cause of the decline and why it had not spread beyond peninsular Florida could not be answered, 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.
All of this remains speculation, but fits the situation from 2017. More importantly, the ideas pondered by the group can be tested and researched as we move forward into 2018. 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. While this may not solve what happened last season, it is the best way we know today to produce a good crop of peanuts. As our meeting concluded, no one shrugged and said, “I don’t know.” Researchers and specialists were united in solving this problem for growers in Florida and across the Southeast.