Response of annual weed species to glufosinate and glyphosate

The recent introduction of glufosinate-resistant. and glyphosate-resistant. crops provides growers with new options for weed management. Information i s needed to compare the effectiveness of glufosinate and glyphosate on annu al weeds. Greenhouse trials were conducted to determine the response of bar nyardgrass (Echinochloa crus-galli), common lambsquarters (Chenopodium albu m), common ragweed (Ambrosia artemisiifolia), fall panicum (Panicum dichoto miflorum), giant. foxtail (Setaria faberi), large crabgrass (Digitaria sang uinalis), and velvetleaf (Abutilon theophrasti) to glufosinate and glyphosa te. The response of velvetleaf and common lambsquarters was investigated at multiple stages of growth. Glufosinate and glyphosate were applied to each weed species at logarithmically incremented rates. The glufosinate and gly phosate rates that provided a 50% reduction in aboveground weed biomass, co mmonly referred to as GR(50) values, were compared using nonlinear regressi on techniques. Barnyardgrass, common ragweed, fall panicum, giant foxtail, and large crabgrass responded similarly to glufosinate and glyphosate. Comm on lambsquarters 4 to 8 cm in height was more sensitive to glufosinate than glyphosate. In contrast, 15- to 20-cm tall-velvet leaf was more sensitive to glyphosate than glufosinate.