Narrative:

We were descending into sioux falls and had been told to descend to 6;000 feet. As we were descending through roughly 7;000 feet I looked ahead and noticed an airplane headed directly towards us. It was a yellow crop dusting aircraft. Right about the time I saw the airplane and prepared to respond to what I assumed to be an upcoming RA the cropduster began a climbing turn towards our right. The airplane passed off our right hand side probably within 500 feet. We never received any traffic advisory from ATC and never received either TCAS RA or TA. After the plane had passed we advised ATC of the aircraft and they told us they didn't show any primary targets anywhere near our position. We continued on and had a normal landing at fsd. Cropdusting aircraft most likely did not have a transponder and was not talking to ATC. I do not believe anything done by us could have prevented this from occurring.

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Original NASA ASRS Text

Title: A flight crew reported an NMAC with a non-transponder equipped aircraft on descent into FSD.

Narrative: We were descending into Sioux Falls and had been told to descend to 6;000 feet. As we were descending through roughly 7;000 feet I looked ahead and noticed an airplane headed directly towards us. It was a yellow crop dusting aircraft. Right about the time I saw the airplane and prepared to respond to what I assumed to be an upcoming RA the cropduster began a climbing turn towards our right. The airplane passed off our right hand side probably within 500 feet. We never received any traffic advisory from ATC and never received either TCAS RA or TA. After the plane had passed we advised ATC of the aircraft and they told us they didn't show any primary targets anywhere near our position. We continued on and had a normal landing at FSD. Cropdusting aircraft most likely did not have a transponder and was not talking to ATC. I do not believe anything done by us could have prevented this from occurring.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.