When it came to disease pressure this year, peanuts in Virginia and North Carolina fared better compared to previous seasons when disease was a real problem for many growers. Dry weather and good management are credited for the improvements.
“For leaf spot control, people did a lot better this year. They kept on top of their sprays more and got better at rotating and mixing chemistries. Some people started earlier. They did a five-spray versus a four-spray program. That’s helped,” said Dr. Hillary Mehl, Extension plant pathologist at Virginia Tech.
As in Virginia, North Carolina fared better with leaf spot pressure this year compared to prior years. Dr. Barbara Shew, Extension plant pathologist at North Carolina State University, credited dry weather and better control by growers.
Speaking at the Peanut Variety Quality Evaluation (PVQE) Tour at Taylor Slade’s farm in Williamston, N.C., Sept. 12, Mehl said leaf spot research efforts at Virginia Tech are focused on a number of different control programs. Mehl and her colleagues are looking at a five versus a four-spray program, comparing advisories to calendar-based sprays and are evaluating different chemistries.
“We are seeing a lot of leaf spot in our untreated controls now. We’re seeing up to 100 percent of the canopy with lesions and about 40 percent defoliation in some of our untreated controls. We have some really high leaf spot pressure in our research trials which is good for comparing products.
“We’re seeing some good differences between different fungicide programs so I am anticipating at the end of the season we will have some nice data to look at comparing different chemistries, different fungicide programs, different number of sprays to see what’s working best,” Mehl said.
In previous years, better leaf spot control was achieved from a five-spray program compared to a four-spray program. “But when it comes to yield, we’re not really seeing a difference between a four and a five-spray program, even if it’s a difference in leaf spot severity of say five percent versus 40 percent at digging,” Mehl said.
Virginia Tech is encouraging peanut farmers to make the most cost-effective use of their fungicides and also rotate and mix chemistries for better leaf spot control, so they won’t lose the effectiveness of different fungicides currently available.
Mehl and Shew urged peanut farmers to practice good fungicide stewardship, because while there are new products on the market, there are no new chemistries. “It’s going to be really, really important to practice good stewardship so we don’t lose any of the activities we have right now,” Shew said.
In the meantime, both Shew and Mehl reported greater stem rot pressure and outbreaks this year. “Most of the calls I received this year were about stem rot. That’s not at all surprising with the weather we had and the cycling we had between heat and thunderstorms,” Shew said.
Mehl said Virginia saw quite a bit of stem rot at mid-season this year from mid-July to mid-August because of all the hot weather. Peanut plants have shown signs of the disease with fungal growth, but both Mehl and Shew emphasized that doesn’t mean there is severe infection.
Both said the impact of stem rot won’t be known until the peanuts are dug.
When it comes to weeds, Dr. David Jordan, North Carolina State Extension peanut specialist, noted that peanut fields are a lot cleaner this year, compared to the past two years. He credits farmers investing more in herbicide programs.
“We talked a lot about rouging out ragweed and pigweed just in case they are PPO-resistant. Hopefully, we will continue doing that and we can deplete the soil seed bank and make progress there. I also think some of the weed control benefits we see in peanuts is that there’s been a really strong push to help people do a good job in other crops. Auxin materials are probably having an effect on some of our populations in cotton and soybeans that might be in a peanut rotation,” Jordan said.
“We don’t need to be complacent, but I think we’re making good strides in our weed management. But you can ride down the road and find a weedy field. There are still some out there, but I think we’re doing a better job in that area.,” he noted.