• By Ethan Carter, De Broughton and Nick Dufault •
As we near the end of August, many peanut fields in the Panhandle range from 100 to 125 days after planting (DAP). This late in the season, some growers are starting to do maturity checks, contemplate digging dates and examining product labels for the preharvest interval rates.
Although growers have been battling wet weather and diseases like leaf spots and white mold all season long, one disease that they may not have on their radar is peanut rust. This disease is generally uncommon in Florida. However, in recent years has shown up in late August to early September.
The wet weather and possible cooling this time of year, will create optimal environments for this disease, if it is present. It will be important to scout and use the proper late season fungicides to help manage this disease.
Peanut rust found in Suwannee Valley
Peanut rust was found in Florida research plots in the Suwannee Valley this week. This is about a week earlier than when it was reported last year.
Rust infestations can start small, but if not found and treated within a week or two can snowball into a full-blown management issue. Rust pustules form on the underside of peanut leaves and can be viewed with the naked eye or a hand lens.
Research from 2014, a year when rust incidence reached nearly 100% in untreated test plots, showed that treatments of azoxystrobin (e.g. Abound) and pyraclostrobin (e.g. Headline) were very effective at managing peanut rust. Treatments that had chlorothalonil (e.g. Bravo) and tebuconazole (e.g. TebuStar) also provided adequate rust management.
However, only the chlorothalonil and pyraclostrobin treatments provided adequate late leaf spot management as well. It is also important to note that farmers using the leaf spot fungicide Miravis will need to combine it with a fungicide that has additional activity on rust, if this disease is present in the field. Some brand name products (e.g. Elatus, Fontelis) may also be effective against rust, but due to the sporadic nature of this disease there is limited data available about their efficacy in Florida.
Learn more by reading: “The What, When and How of Florida’s Peanut Rust Issue”
Ethan Carter is the regional row crop IPM agent based in Jackson County, Florida. De Broughton provides Extension and education for North Florida farmers focusing on the agronomic crops of peanut, corn, soybean and small grains. Dr. Nick Dufault is an Extension plant pathologist. All are with the University of Florida.