Field studies were conducted near College Station, TX, in 2006 and 2007 to evaluate the economic impact of common sunflower interference in field corn. A density of one common sunflower per 6 m of crop row caused a yield loss of 293 kg ha−1. Estimated losses at a net corn price of $0.08 kg−1 was $92 ha−1 for infestation levels of four common sunflower plants per 6 m of row. Corn yield was increased by 32 kg ha−1 by each 1,000 plant ha−1 increase in corn planting density. Corn planting densities of 49,400 and 59,300 plants ha−1 provided the greatest net returns with or without the presence of common sunflower competition. Corn yields were reduced by extended duration of sunflower competition, with losses exceeding 1,500 kg ha−1 per week and increasing in magnitude at a decreasing rate throughout the growing season. Herbicide treatments provided net returns of $600 to $1,300 ha−1 above no weed control in both 2006 and 2007. Net returns of $609 and $653 ha−1 were obtained without the use of any herbicide for sunflower control. Determining the economic impact of common sunflower interference in field corn allows producers to estimate the overall net return on the basis of duration of common sunflower interference and density, while considering varying net corn prices, crop planting density, and herbicide application costs.

Annual bluegrass is a troublesome weed in golf course putting greens. The objective of this research was to evaluate creeping bentgrass putting green tolerance to bispyribac-sodium tank-mixed with paclobutrazol in the transition zone. Field trials with four replications were conducted in Oklahoma during 2009 and 2010 and in Missouri during 2010. The results of this study suggest that tank-mixing bispyribac-sodium with paclobutrazol may discolor creeping bentgrass putting greens but will not reduce turf quality below acceptable levels. Normalized vegetative difference index readings indicated no treatment differences in turf greenness at 4 and 8 wk after initial treatment. Weekly application of bispyribac-sodium at 12.4 g ha−1 or biweekly application at 24.8 g ha−1 alone or with monthly applications of paclobutrazol at 224 g ha−1 did not cause unacceptable injury to creeping bentgrass putting greens during the spring.

Cleavers species (false cleavers and catchweed bedstraw) are among the top 10 most abundant weeds across the prairie region of western Canada, and are increasing in relative abundance at the fastest rate since the 1970s. In 2008, two false cleavers populations from Tisdale and Choiceland, Saskatchewan, were suspected of acetolactate synthase (ALS) –inhibitor resistance. Dose-response experiments were conducted with the use of imazethapyr and florasulam, both ALS inhibitors, as well as fluroxypyr, a synthetic auxin. Additionally, a 1,954–base-pair region of the ALS gene including sites known to confer ALS resistance were sequenced. Both populations were highly resistant to imazethapyr (resistance factors greater than 100), one population (Tisdale) was highly resistant to florasulam (Choiceland population susceptible, although a second, larger screening of 200 individuals indicated low frequency [2%] florasulam resistance), and both populations were susceptible to fluroxypyr. All sequenced Tisdale individuals screened with imazethapyr posessed the Trp574Leu mutation. In contrast, three point mutations were found for Choiceland individuals sequenced: Ser653Asn, Trp574Leu, and Asp376Glu. These ALS target-site mutations have not been documented previously in this species.

Wild buckwheat is the most abundant broadleaf weed across the Prairie region of western Canada. Acetolactate synthase (ALS)-inhibiting herbicides are commonly used to control this species and other broadleaf weeds in cereal crops. A field survey in Alberta in 2007 identified a single population that was putatively resistant to ALS-inhibiting herbicides. In herbicide resistance screening in the greenhouse, all F1 progeny tested were resistant to the ALS-inhibiting herbicides thifensulfuron/tribenuron, a sulfonylurea herbicide, or florasulam, a triazolopyrimidine herbicide; dose response of shoot biomass indicated the population was 10- and 20-fold less sensitive to thifensulfuron/tribenuron and florasulam, respectively, than a susceptible control population. ALS gene sequencing of 24 F1 progeny indicated that the Trp574Leu target-site mutation was responsible for conferring ALS-inhibitor resistance in this biotype, the first global report of ALS-inhibitor resistance for this species. Because this mutation typically endows high-level resistance across all five ALS-inhibitor classes, this wild buckwheat biotype may only be controlled by a different site-of-action herbicide.

Organic growers need additional tools for weed control. A new technique using abrasive grit propelled by compressed air was tested in field plots. Grit derived from corncobs was directed at seedlings of summer annual weeds growing at the bases of corn plants when the corn was at differing early stages of leaf development. Season-long, in-row weed control exceeded 90% when two or three abrasion events were coupled with between-row cultivation. Timing of weed abrasion was critical, with highest levels of control corresponding to the one- and five-leaf stages or the one-, three-, and five-leaf stages of corn development. Corn yields associated with these treatments were equivalent to those of hand-weeded controls in which no abrasive grit was applied. Thus, air-propelled abrasive grit applications at the one-, three-, and five-leaf stages of corn controlled weeds sufficiently to prevent weed-induced reductions in corn grain. Additionally, these applications were not harmful to corn plants. This new concept for weed control may be of interest to organic crop managers.