Soybean rust outbreak thwarted by warning system and weather

Editor’s note: the reference to the timely updates and observations about when best to spray, toward the end of this page, refers to a national system called the ipmPIPE. The ipmPIPE began with soybean rust, but now there are PIPEs for other crops. For more information about the ipmPIPE and what crops have similar alert systems for pests or diseases, go to

Story by Roy Roberson

Soybeans and wheat made an awesome economic combination for growers in the Southeast this past growing season, creating plenty of optimism for profits from this year’s beans and optimism for planting more of the crop in 2013.

Even the earliest appearance on record of Asian Soybean Rust did little to slow down what is shaping up to be one of the best soybean crops on record in some parts of the Upper Southeast.

Rust was detected along a southern tier of North Carolina counties on Sept.12, but Mother Nature, a well-coordinated system of sentinel plots, and timely actions by growers stopped rust in its tracks.

Though the disease was documented on Sept. 12, in North Carolina, the earliest on record by three days, it appears there was little damage to the state’s 1.65 million acre soybean crop.

Duplin County, N.C., Extension Agent Curtis Fountain says once the disease was detected in counties less than 100 miles from his area, growers quickly reacted and applied fungicides when needed.

Fountain says, “Remember the disease triangle/pyramid (host, pathogen, and favorable environment). All 3 are needed for disease development and spread. In other words, host + pathogen + favorable environment = disease. Obviously time is required as well.

North Carolina State University Plant Pathologist Steve Koenning and Soybean Specialist Jim Dunphy issued timely updates on movement of the disease and provided virtually day-to-day observations on when and what to spray to best manage ASR.

Koenning says soybeans that have just reached full bloom (stage R2) typically have 65 days until they’re safe from rust or frost (stage R7), if they are full-season soybean, or closer to 55 days if they are double-crop soybeans.

If soybean plants have small pods in the top, (stage R3), they have 55 and 47 days, respectively, to R7. With full sized pods in the top of the plants (stage R4), they have 45 and 38 days, respectively, until R7.

From stage R5 (small seeds in the top of the plant) they typically have 35 and 30 days, respectively. From stage R6 (full sized seeds in the top of the plants), they typically have 20 and 17 days, respectively.

Read the rest of the story at Southeast Farm Press

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