Abstract: Embodiments of the present disclosure relate generally to kits for identifying herbicide resistant plants and methods for determining whether a plant is herbicide resistant. The methods are based on the discovery that some genes are over-expressed or under-expressed in herbicide resistant plants when compared to herbicide-sensitive plants prior to application of the herbicide. The methods include determining the expression level of the one or more genes of interest in a biological sample, such as via qRT PCR, and determining whether the biological sample is from an herbicide-resistant plant based on the expression level. In an embodiment, the kit and methods are used to identify glyphosate-resistant Ambrosia trifida. The kits and methods can be used to improve crop management strategies.