The latest discovery of Asian soybean rust is in a sentinel plot in Escambia County in Florida’s western panhandle. The rust was found on July 18 and confirmed on July 19.

“Earlier this year, we set up sentinel plots (all planted in Group 3s, 5s and 7s) from Homestead all the way out to Escambia County,” said Jim Marois, Florida Extension plant pathologist on Tuesday. “The plot that came up positive is in the northwest corner of Escambia County. To give an idea of the area, Pensacola is in southern part of the county.”

Escambia County is also adjacent to Alabama’s Baldwin County where rust has also been found in a sentinel plot and commercial field. “If you look at a map, the Mississippi rust site in George County isn’t that far away either. There’s a cluster along the coast where rust suddenly popped up.”

The Escambia plot is the second in Florida infected with rust. The disease was first discovered several weeks ago in Citra, south of Gainesville in Marion County. In that plot, rust was found on Group 3s at R-4/R-5. Marois said rust at the Citra site is now spreading to the Group 5s and 7s.

In Escambia County, rust was found on two Group 3 plants. “Rust was found on their second and third trifoliates with a lot of disease on them. There was also a Group 5 leaf ‘hanging over’ the Group 3s that was infected.

“I think what’s happening at Citra – and we’ll likely see it at Escambia too – is as the inoculum builds, the Group 5s and 7s are becoming diseased too. Currently, since they aren’t as far along in the maturation process, they aren’t as susceptible as the Group 3s.”

The Escambia County sentinel plot, scouted weekly, is inside a 200-acre commercial soybean field planted about a month ago. The plot is of “substantial size and we only found rust on two plants. On the plants that came up positive I’d say the severity rate is ‘low to moderate.’ However, the leaves, as few as they are, had over 100 lesions on them.”

Florida Extension is recommending producers in the western panhandle counties – Escambia and Santa Rosa – consider spraying a fungicide as their plants come into bloom. Most soybeans in the state aren’t yet at bloom stage.

“They probably won’t be there for another 10 days or so,” said Marois. “That allows many producers a few days to get their ducks in a row.” Producers need to be on a “high alert” with scouting.

“Look carefully,” said Marois. “There isn’t enough profit in soybeans to spray a bunch of fungicides you don’t need. But if you find the disease in your field, you need to spray. Once this rust gets on the plants, it really takes off.”

e-mail: dbennett@primediabusiness.com