Suppression of Trifolium repens in Poa pratensis Using Sequential Application of Systemic and Contact Herbicides

ABSTRACT Trifolium repens L. (white clover) is a common perennial weed that aggressively colonises turfgrass, disrupting its uniformity and aesthetic quality. Effective management of T. repens is essential for preserving the visual and functional integrity of turfgrass systems. This study evaluated the efficacy of a sequential herbicide application strategy for controlling T. repens in Poa pratensis L. (Kentucky bluegrass). A randomised complete block design with three replications and nine treatments was employed, comprising systemic herbicides—U46‐Combi Fluid (U) (containing 2,4‐D and MCPA) at 1.5 and 2 L ha −1 (1012.5 and 1350 g ai ha −1 ), and Duplosan Super (D) (containing MCPA, Dichlorprop‐P, and Mecoprop‐P) at 2 and 2.5 L ha −1 (1200 and 1500 g ai ha −1 )—followed by a contact herbicide, Ioxynil (I), at 0 or 2 L ha −1 (0 and 4500 g ai ha −1 ). Results showed that the D2.5 + I2 and D2 + I2 treatments achieved 100% weed control efficiency and complete suppression of T. repens regrowth, significantly reducing its biomass while enhancing P. pratensis visual quality, chlorophyll content, and biomass. Correlation and principal component analyses highlighted strong negative associations between weed ( T. repens ) and turfgrass ( P. pratensis ) metrics. These high‐performing sequential treatments represent an effective and practical approach to T. repens management. This approach's key advantage lies in preventing weed regrowth, which can reduce the need for repeated applications and thereby lower the overall herbicide load in turfgrass systems. Further research should investigate the long‐term ecological and economic implications of this method, as well as its adaptability across various turfgrass species and environmental conditions.