The Boy Scout motto “Be prepared” certainly applies to preparing for the future availability of crop protection products due to the uncertainty from regulatory pressures and resistance issues. 

A case in point is possible loss of tools as the U.S. peanut industry tries to capture international markets. The European Union’s banning the use of the fungicide chlorothalonil due to environmental concerns surrounding the compound.  

The EU’s Standing Committee on Plants, Animals, Food and Feed (PAFF Committee) called for the ban of chlorothalonil. The ban in the EU began in 2020. 

In field days and grower meetings, North Carolina State University Extension Peanut Specialist David Jordan has stressed that the EU chlorothalonil ban is something peanut growers need to keep on their radar screens. As of now, the EU is not banning imports of peanuts from the United States and other countries that use chlorothalonil, but U.S. peanut farmers need to be prepared and aware.

Jordan has emphasized that he is not anticipating a ban by the EU of U.S. peanuts where chlorothalonil was applied, but he cautions it could happen and farmers need to be prepared and consider other disease management options beyond using chlorothalonil.  

Jordan says the challenge for the U.S. peanut industry is that shellers are not able to segregate peanuts that have been treated with chlorothalonil with those where the compound has not been applied. He has emphasized that “Bravo” — or chlorothalonil — is a safe compound that serves a vital role in peanut production.

Finding alternate options 

Jordan said the EU is considered a key export market for U.S. peanuts so N.C. State is researching fungicide control options such as rotations, cover crops, and sulfur in case chlorothalonil can no longer be used by U.S. peanut farmers.  

“Those are all tools that we want to look at in case really bad things come along where we don’t have the tools,” he said. 

Jordan and his team are evaluating 10 different peanut varieties (both runners and Virginia-types) with five different fungicide programs for each of the varieties. In addition to standard fungicide programs, the researchers are evaluating a sulfur product that’s available in the market and comparing it to the use pattern for chlorothalonil.  

The idea is to see how well the sulfur product works when part of a fungicide program. A key aim of the research project is to see which of the 10 varieties in the project face the greatest risk with a less than ideal fungicide program. 

Graduate research assistant Ethan Foote, speaking at the late season peanut disease tour Sept. 27 at the Peanut Belt Research Station in Lewiston-Woodville, says N.C. State is evaluating 10 different peanut varieties (both runners and Virginia-types) with five different fungicide programs for each of the varieties. (Photo by John Hart)

At a late-season disease management tour at the Peanut Belt Research Station in Lewiston-Woodville Sept. 27, Jordan and graduate research assistant Ethan Foote highlighted the research project that is now in its second year. 

Foote said they are evaluating 10 different varieties, seven Virginia-types and three runner types. As of the Sept. 27 field day, Foote hasn’t finished the various disease ratings from this year’s trial, but he did highlight findings from last year’s research. 

The research includes an untreated check and a sulfur versus chlorothalonil five-spray program conducted throughout the peanut growing season. Other fungicides were also included in the research, in addition to chlorothalonil and sulfur. 

“Last year, our greatest increase in defoliation was with our untreated plot. The best performance was the chlorothalonil spray straight through. There was similar performance with the rotation of chemistries, whether it was sulfur or chlorothalonil at the beginning.  Where we really stretched the sulfur is where we had that five-spray program of sulfur alone. It couldn’t hold up during the season compared to the Bravo sprays,” Foote said. 

The researchers also examined the different fungicide programs when the peanuts were planted in a standing rye cover crop and compared it to peanuts placed on bare ground. Foote said the rye cover crop was terminated but left in the field where the peanuts were planted. The research was conducted at both the Peanut Belt Research Station and the Upper Coastal Plain Research Station in Rocky Mount. 

“There was less disease in our rye standing cover crop. There’s a barrier on the ground compared to bare ground where there was greater disease pressure and defoliation,” Foote said. 

Spray options 

While there was less disease pressure, Foote said the rye plot saw a significant yield drop of 20%, compared to peanuts planted on bare ground. And what does Foote attribute the big yield drop to? 

“It could be digging efficiency. It could be early season competition. We left the rye standing and planted straight through. It was killed in early May and then planted in mid to late May. Rye has a lot of biomass, a lot of it is still standing in the field.  It could be competition for resources, mostly sunlight. It could be shaded out,” Foote said. 

“In one of the tests we had seven different fungicide programs. We included a three-spray program to see how that rye performed. With that compared to the chlorothalonil versus sulfur spray, Bravo is going to outperform when you have it a five-way program and even in a three-spray program,” he said. 

In the three-spray program there was a great deal more disease pressure compared to the five-spray program. Foote said a start to finish five-spray sulfur versus chlorothalonil program, rotated with other chemistries, was the best performer.   

Jordan added that the five-spray sulfur program worked pretty well. While the program may perform well in North Carolina, Jordan said the program won’t work that well further south in the peanut belt, Georgia, and Alabama. “The sulfur doesn’t hold up for them like it does for us. We don’t have the intensity of disease for as long as they do.”