Selective Tall Fescue Control in Kentucky Bluegrass Turf with Diclofop1

Abstract

AbstractTall fescue (Festuca arundinacea Schreb.) is an objectionable weed in Kentucky bluegrass (Poa pratensis L.) turf. Currently, there are no herbicides registered for selective control of tall fescue in Kentucky bluegrass. The objectives of these field studies were to determine safe and effective rates of diclofop {(±)‐2‐[4‐(2,4‐dichlorophenoxy) phenoxy] propanoic acid} for selective control of tall fescue in a ‘South Dakota Certified’ Kentucky bluegrass turf grown on a Chillum silt loam (fine‐silty, mixed, mesic Typic Hapludult). A total of three applications of diclofop during spring and fall at rates of 2.2, 3.4, or 4.5 kg ha−1 provided > 90% tall fescue control. The 4.5 kg ha−1 rate was more effective (98 or 99% control), but normally caused a reduction in Kentucky bluegrass cover. Diclofop was most injurious when applied to Kentucky bluegrass less than one year of age. Mature turf sustained much less injury from high rates of diclofop. The 2.2 kg ha−1 rate was generally safer to the turf than 3.4 or 4.5 kg ha−1, and the level of tall fescue control ranged from 91 to 96%. Diclofop stunted and discolored the Kentucky bluegrass turf. These effects generally persisted for 2 to 3 weeks. More information is needed regarding the relative sensitivities of Kentucky bluegrass cultivars to diclofop, as well as the influence of water dilution on the safety of diclofop's use