The first U.S. sighting of soybean rust on soybeans for the current growing season was made this week in a sentinel plot in central Alabama’s Autauga County.

The disease was detected in a soybean sentinel plot in Prattville in Autauga County on Aug. 3. According to Ed Sikora, Auburn University Extension plant pathologist, the soybeans were at the R5 growth stage with 100 percent canopy closure. Incidence of soybean rust within the plot was less than 1 percent. The disease was previously reported on kudzu in Baldwin County, near the Alabama Gulf Coast. 

Weather conditions have been more favorable for soybean rust development in the past week, says Sikora, however, low overwintering inoculum levels appear to have resulted in a slow build-up of the disease this year.

Soybean rust was found on kudzu in Leon and Jackson counties in Florida during the last week of July. It has now been detected in eight counties in central and north-central Florida. The disease has also been observed on kudzu in southern Louisiana.

While this first report of soybean rust on soybeans in Alabama should be noted, growers should be paying greater attention to frogeye leaf spot (FLS), says Sikora.

“FLS has been observed throughout the state in commercial fields and sentinel plots. Growers with FLS susceptible to moderately tolerant varieties should strongly consider applying a tank-mix fungicide combination at the R3 growth stage before the disease appears in the field. Applying a fungicide after FLS appears in the field is not an effective method of controlling this disease. 

More information can be found at the ipmPIPE website.

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