Metribuzin Tolerance Screening for Kentucky Soybeans

Abstract: Metribuzin is a widely used herbicide in soybean (Glycine max L.) produc on due to its broad-spectrum control of problema c weeds, especially pigweeds. However, soybean cul vars vary considerably in their tolerance to metribuzin, and sensi vity can result in stand loss, delayed emergence, chlorosis, and reduced yield. Screening soybean lines for both pre- emergent and post-emergent metribuzin tolerance is therefore cri cal for developing resilient cul vars and ensuring sustainable weed management strategies. Pre-emergent exposure to metribuzin can impair seedling establishment by inhibi ng photosystem II ac vity shortly a er germina on, par cularly under cool, wet, or low organic ma er soil condi ons that increase herbicide availability. Iden fying soybean lines with pre- emergent tolerance allows growers to mi gate early-season injury risks and improve stand uniformity. Similarly, post-emergent metribuzin applica ons can cause foliar damage, reduced photosynthe c capacity, and growth suppression, especially in sensi ve genotypes. Screening for post-emergent tolerance enables the selec on of lines capable of withstanding in-season herbicide stress without compromising produc vity. Evalua ng tolerance at both growth stages is essen al because gene c mechanisms governing pre- and post-emergent responses may di?er, and tolerance at one stage does not necessarily predict tolerance at another. Comprehensive screening facilitates the iden ?ca on of stable, broad-stage tolerance aimed at improving herbicide safety margins. Ul mately, incorpora ng metribuzin-tolerant soybean lines into produc on systems enhances weed control ?exibility, reduces yield losses associated with herbicide injury, and contributes to more reliable and economically viable soybean produc on across Kentucky.