Multi‐state survey to identify suspected resistance to four herbicides and one plant growth regulator in Poa annua.

Plain Language Summary: Poa annua is a troublesome weed in turfgrass areas such as golf courses, athletic fields, lawns, and sod farms. Controlling P. annua is made more difficult by the growing problem of herbicide resistance, the inherited ability of plants to survive herbicide applications that would normally be lethal. Researchers from 13 academic institutions collected 866 P. annua populations from different states and turfgrass systems to better understand the extent of this problem. Collections were divided and treated with four herbicides and one plant growth regulator. Plants were categorized as “susceptible” or “suspected resistant” based on their response to treatments. Suspected resistance (to at least one or more treatments) was observed in 16.8% of P. annua collections. Herbicide resistance in P. annua is a problem spanning different geographies and management practices. Therefore, coordinated research is needed to explore the scope and nature of the problem in a systematic way. [ABSTRACT FROM AUTHOR]