In a Nutshell: 40 Years of Tackling Peanut Diseases

Brenneman wraps up career as plant pathologist at UGA

by Joy Crosby

Lessons like knowing where to park your truck, phrases to never say and how to expect the unexpected are all lessons University of Georgia plant pathologist Tim Brenneman found valuable during his 40-year career. The career also led him to help farmers develop disease management plans and discover pecan truffles.

One of the most important lessons Brenneman learned through his years of research is where to park his truck in a field with an irrigation pivot. Also, he learned to never assume that a pivot will not be moved, even right after peanuts are dug.

Brenneman recalls parking his truck in Jud Greene’s field in Decatur County and walking through the field to capture disease ratings. Greene was planting a winter cover crop, so he was moving the pivot in the field. Brenneman noticed the pivot moving right towards his university truck, so he had to take off running through the field to move his truck before the pivot walked over it.

Through the years, Brenneman has learned that biological systems like peanut fields are constantly changing and nothing is constant. Also, biological systems like peanut fields are extremely complex, he adds.

Brenneman has also learned to never say never, especially when discussing Cylindrocladium Black Rot (CBR). The disease was first found in Terrell County, Georgia, in 1965 and could be devastating to peanut fields that had not been fumigated. Brenneman told farmers that the microsclerotia that form can live in the soil a long time and spreads from field to field.

"I would tell the farmers that if you get CBR in your fields, then it will be there until you die," Brenneman says. "However, I've learned to never say never, since that ended up not being true."

Through research, plant pathologists discovered that CBR was seed transmitted. New fungicides were developed and applied infurrow to help manage the disease. There were also biological reasons that CBR went away. According to Brenneman, CBR is no longer a significant problem and mostly gone now for most all the Southeastern states.

However, the disease is now an issue in the Midwest and known as red crown rot and an emerging threat to soybean production.

Another issue concerning peanuts Brenneman was critical in solving involved seed disease issues in 2020.

"The foundation of our industry begins with the seed," Brenneman says. "We need good stands to get good crops, and good seed equals good stands."

Seed treatments are critical to the success of the peanut industry. When fungicide-resistant Aspergillus threatened the 2020 seed supply, Brenneman was at the forefront of introducing new seed treatments and in-furrow sprays to control it. He also helped develop the first polymer coating for peanut seed in Georgia.

White mold is a disease Brenneman has carefully researched for many years. Brenneman reminds growers that controlling white mold

takes a package approach of rotation, partially resistant cultivars, late planting and fungicide applications.

Brenneman recalls when he first came to Georgia in 1986 how growers used 100 pounds per acre of a granular product called Terraclor which only provided 20 to 30 percent control of white mold. According to Brenneman, the granular product was very expensive and time consuming to apply down through the canopy of the peanut plant.

Then in 1994, a game changer came along for farmers by the name of Folicur.

"Folicur was the first sprayable fungicide offered to control foliar and soilborne diseases," Brenneman says. "This was a new paradigm for growers."

Through the years more fungicides were developed including products with different chemistries and modes of action, and growers today have a variety of options.

However, Brenneman warns growers that new fungicides are great, but they are not bullet proof. One of the main reasons fungicides do not control white mold is through application where the fungicide may never reach the target site.

According to Brenneman, there are two methods of getting fungicides down to where white mold infects the plant and that is through night spraying when the leaves are folded and/or washing it down with irrigation.

Brenneman first observed night spraying in Nicaragua and decided to try the technique in the United States on his research plots. Through his research, Brenneman discovered that if farmers apply fungicides for white mold control just before daylight with dew on the leaves, then the fungicide will be able to get more to the crown of the peanut plant to control white mold. This is especially important for dryland growers.

One of Brenneman’s favorite studies of his career was conducted with Jason Woodward, PhD student in 2006. Through the study, they looked at how to wash fungicides down for white mold and still maintain control of leaf spot on the foliage. The results from their study resulted in the recommendation of applying irrigation about 18 to 24 hours following a fungicide spray to achieve maximum redistribution of the fungicide for the best control of both leaf spot and white mold.

"The greatest advance coming down the road is the miracle of resistance with genes from the wild species," Brenneman says. "Resistance genes from wild species in South America have paved the way for breeders to incorporate many valuable traits into our commercial peanuts."

These new genes opened the door to all of the nematode resistant lines farmers use today such as Georgia 14-N, TifNV-HiOL and TifNV-HG. These have revolutionized nematode control, replacing expensive nematicides, and even better ones are on the way.

As retirement draws near for Brenneman, he reflects on his 40-year career involving disease management for peanut and pecan farmers.

"What truly excites me is walking into a field, identifying a serious disease issue, and working with the farmer to find a solution. I feel incredibly blessed to have worked with some amazing colleagues in an industry I've loved being a part of," Brenneman says. "Hopefully, the impact of all of these different pieces coming together will give farmers some tools to help manage diseases and stay profitable."