Greenhouse studies verified that smooth crabgrass from a golf course tee in southern New Jersey was resistant to fenoxaprop-P, although smooth crabgrass from a nearby untreated rough was susceptible to this herbicide. Fenoxaprop-P-resistant plants were injured, however, when fenoxaprop-P was applied at levels above the maximum use rate for turf. Fenoxaprop-P applied postemergence at 0.76 kg ai/ha, four times the maximum rate, reduced shoot weight of the resistant biotype by 35%, whereas application of 1.52 kg/ha, eight times the maximum rate, reduced shoot weight by 64%. Large crabgrass and the susceptible biotype of smooth crabgrass were controlled by fenoxaprop-P applied at 0.1 kg/ha. Fenoxaprop-susceptible and -resistant biotypes of smooth crabgrass had a similar response to MSMA, dithiopyr, and quinclorac applied postemergence. The fenoxaprop-P–resistant smooth crabgrass biotype was controlled by the cyclohexanedione herbicides sethoxydim and clethodim, but the aryloxyphenoxypropionate herbicides fluazifop and quizalofop reduced shoot weight by only 15 to 66% depending on herbicide and rate.

Common reed is an invasive species that has overtaken wetland habitats in the eastern United States and can spread into roadsides, turf, and ornamental sites. The postemergence grass herbicides used in nursery crops and turf, clethodim, fenoxaprop, fluazifop, and sethoxydim, did not control common reed. Dithiopyr, MSMA, and quinclorac also did not control this weed. Glyphosate applied at 2.24 kg ai/ha (2.0 lb ai/ac) was more effective in preventing regrowth of common reed than glufosinate at 1.12 kg/ha (1.0 lb ai/ac). Mowing every 2, 4, or 8 wk controlled common reed 93, 81, and 69%, respectively, by the end of the growing season, but only reduced regrowth by approximately 55% the following May. Applying glyphosate at 2% v/v either 1 mo after a mowing or 2 wk prior to mowing reduced common reed regrowth the following May by approximately 90%. Applying glyphosate without mowing provided similar common reed control the following spring compared to glyphosate combined with a single mowing. Common reed regrew in all treated plots 1 yr after study initiation, indicating that control treatments must be repeated if common reed is to be eradicated from a site.