Site of uptake, absorption, translocation, and metabolism of ethofumesate were studied to determine the differential responses of annual bluegrass, creeping bentgrass, and perennial ryegrass. Using barriers to isolate foliage or soil, the primary site of ethofumesate absorption was found to be the foliage. Symptoms resulting from foliar and over-the-top spray applications of ethofumesate to annual bluegrass included stunting of growth, epinasty, swelling of the crown, darker green color, and fusing of expanding leaf blades. Averaged over the course of the experiment, annual bluegrass, creeping bentgrass, and perennial ryegrass absorbed 33, 11, and 13% of ethofumesate applied. No ethofumesate was detected distally from the treated leaf, but overall translocation of ¹⁴C 14 d after treatment (DAT) was 2.2, 5.8, and 2.2% of the absorbed ¹⁴C for annual bluegrass, creeping bentgrass, and perennial ryegrass, respectively. Ethofumesate was rapidly metabolized in each species with half-lives ranging from 4.5 to 7 d. The three grasses had metabolized, on average, 67% of the absorbed ethofumesate 14 DAT.

Nomenclature: Ethofumesate; annual bluegrass, Poa annua L. POANN; creeping bentgrass, Agrostis stolonifera L. AGSST ‘Penncross’; perennial ryegrass, Lolium perenne L. LOLPE ‘Manhattan II’.