A survey of farmers from six U.S. states (Indiana, Illinois, Iowa, Nebraska, Mississippi, and North Carolina) was conducted to assess the farmers' views on glyphosate-resistant (GR) weeds and tactics used to prevent or manage GR weed populations in genetically engineered (GE) GR crops. Only 30% of farmers thought GR weeds were a serious issue. Few farmers thought field tillage and/or using a non-GR crop in rotation with GR crops would be an effective strategy. Most farmers did not recognize the role that the recurrent use of an herbicide plays in evolution of resistance. A substantial number of farmers underestimated the potential for GR weed populations to evolve in an agroecosystem dominated by glyphosate as the weed control tactic. These results indicate there are major challenges that the agriculture and weed science communities must face to implement long-term sustainable GE GR-based cropping systems within the agroecosystem.

Greenhouse dose–response studies were conducted to determine the effectiveness of PRE and POST applications of saflufenacil on blue mustard, flixweed, Palmer amaranth, redroot pigweed, and tumble pigweed. Weed species did not differ in their responses to saflufenacil applied PRE. Averaged across species, PRE application of saflufenacil at 6 to 30 g/ha reduced weed biomass 82 to 98%, but biomass did not differ among rates of 12 g/ha or higher. POST application of saflufenacil reduced weed biomass by 92%, averaged across species and rates. On the basis of regression analysis, the 90% plant biomass reduction for saflufenacil applied PRE and POST was 9 and 6 g/ha, respectively. Saflufenacil applied PRE reduced population density by 77 to 98%, averaged across weed species; a rate of 9 g/ha reduced population density 90% (DR90) on the basis of regression analysis. Averaged across species, POST application of 6 to 30 g/ha reduced population density by 63 to 93%, but regression analysis indicated that the DR90 value was greater than 30 g/ha. Averaged across rates, saflufenacil reduced the population density of flixweed, Palmer amaranth, redroot pigweed, tumble pigweed, and blue mustard by 49, 64, 67, 73, and 78%, respectively.

Novel forms of selective weed control are needed by many types of growers, but especially by organic growers who are restricted from using synthetic herbicides. Abrasive grit made from corn cobs was expelled from a sand blaster at 517 kPa pressure and aimed at plants of common lambsquarters and corn positioned 300 mm distant. Most small weed plants were killed by one split-second blast of grit, but corn plants suffered little damage by the same treatment. Air-propelled grit made from agricultural residues possibly could be used for selective nonchemical weed control without the need for soil tillage.

Soft rush is a perennial, tussock-forming plant that often infests low-lying grazing areas in Florida. Experiments were conducted to determine the most effective herbicides for control of soft rush. Herbicide treatments included triclopyr + fluroxypyr at 0.43 + 0.15 and 0.86 + 0.30 kg/ha, 2,4-D amine at 1.12 and 2.24 kg/ha, 2,4-D amine + carfentrazone at 1.12 + 0.02 and 2.24 + 0.02 kg/ha, aminopyralid at 0.12 kg/ha, and 2,4-D amine + dicamba at 1.61 + 0.56 kg/ha and were applied to soft rush with and without mowing to a 15-cm stubble height. Aminopyralid and triclopyr + fluroxypyr did not control soft rush with or without mowing 1 and 12 mo after treatment (MAT). When mowing occurred prior to application, treatments containing 2,4-D provided at least 81% control of soft rush 1 MAT. In contrast, control was no greater than 59% when treatments were applied without mowing soft rush. Mowing had no impact on soft-rush control with herbicides 12 MAT. Applications of 2.24 kg/ha 2,4-D provided at least 90% control 12 MAT, but this was not significantly different from the premix of 2,4-D + dicamba or 2.24 + 0.02 kg/ha 2,4-D + carfentrazone treatments. Therefore, effective control of soft rush can be obtained with the use of 2,4-D amine or products that contain 2,4-D amine.

The interactive effects of nitrogen rate (0, 28, 56, and 112 kg/ha), vine density (0, 1.8, 3.6, and 5.4 t/ha of the cultivar ‘Stevens’), and weed management (preemergence herbicide, postemergence control, inoculation with weed seeds, and untreated) were determined on the recolonization of open spaces caused by localized biomass removal in a newly planted commercial cranberry bed. To assess the effect of the 64 treatment combinations on initial colonization, all cranberry and weed biomass was removed from a randomly selected 930-cm2 area in each plot in Year 1. To quantify recolonization of the disturbed area, the same quadrat was resampled and all plant biomass was collected in Year 2. Cranberry biomass production in the disturbed area increased in a quadratic fashion with increasing N rates for all vine densities except zero. Cranberry biomass in the year after disturbance was positively correlated with cranberry biomass present in the previous year. Weed stem biomass in the year after disturbance was positively correlated with weed stem biomass from Year 1 and negatively correlated with percentage cranberry biomass from Year 1 and Year 2. Less than one-third of the treatment combinations recovered enough to produce at least 200 g/m2 1 yr postdisturbance (a reasonable expectation of biomass production). Growers who have low weed pressure and extensive cranberry cover on their farms can expect that disturbed areas will be recolonized by cranberry vines when they utilize adequate, but not excessive, nitrogen regimes.