Area soybean producers have been dreading the appearance of Asian soybean rust for a couple of years and now their wait is over.

Soybean rust was detected last week in Tulsa County, Okla., according to USDA but, for now at least, hot weather is slowing progression of the disease and Oklahoma State University agriculturalists are not advocating a fungicide application yet.

They caution, however, that treatment must take place before infection exceeds 10 percent in a give field so scouting is critical.

Rust was found in Tulsa County in a sentinel plot with soybeans at the R6 stage at an incidence rate of 1%. Rust was also found in the sentinel plot in Choctaw County (where rust was found earlier in a commercial field) at 2%.

Sentinel plots in Okmulgee, Ottawa, and Washington Counties remained negative for rust last week. Several irrigated fields in Muskogee County were also visited and found to be negative for rust.

Current weather conditions and those forecasted for next week will not favor rust or even crop development due to hot and windy conditions that are expected statewide with temperatures reaching triple digits in some areas.

Most early-maturing soybean varieties (MG3 and MG4) are at R5 to R6, having mostly advanced past the growth stages at risk to rust damage. Full-season varieties (MG5 and MG6) are from vegetative stages to R1 and remain at risk to rust damage.

Oklahoma state rust officials are recommending suspending fungicide treatments for rust due to the excessive heat and approaching triple digits. This weather is not conducive to further rust development and soybeans are beginning to show signs of moisture stress.

Fungicide application to heat and drought stressed soybeans is not likely to prove productive. Decisions to spray for rust should be reevaluated when the weather moderates after considering crop condition and yield prospects.

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