Sulfentrazone adsorption and mobility in six soils with varying soil properties were evaluated under laboratory conditions. Adsorption was evaluated using a modified slurry technique. Mobility was evaluated using packed-soil columns under saturated flow conditions. The order of adsorption to soil was Sequatchie loam > Dothan loamy sand = Bosket fine sandy loam > Malden loamy sand > Commerce silty clay loam > Harkey clay loam. Greater sulfentrazone adsorption occurred in soils with lower pH. Sulfentrazone movement under saturated flow conditions in 27-cm soil-packed columns was greater in soils with low adsorption, high pH, and coarse texture. Sulfentrazone movement was limited in the Sequatchie loam but was greater in the other soils examined. No clear relationship was evident between sulfentrazone mobility and adsorption in these soils.

Field research was conducted to evaluate plant growth-regulator efficacy for tall fescue growth and seedhead suppression applied using application placement equipment. Specially designed equipment outfitted with fluid application systems applies low-volume plant growth regulator directly on plant foliage, reducing opportunity for drift and visible application. Wet-blade mowers are equipped to apply plant growth regulators and mow in a single pass, whereas rotary-wick applicators simply wipe chemicals directly on uncut vegetation. Therefore, a wet-blade, rotary-wick, and broadcast sprayer system were chosen to apply imazapic at three rates (9, 35, and 53 g ai/ha), and a mefluidide + chlorsulfuron tank mix at 7 + 140 g ai/ha to tall fescue roadsides for vegetative growth and seedhead suppression. Experiments were conducted during the spring and summer of 2004 in central and western North Carolina. Tall fescue was slightly injured and discolored by all treatments but fully recovered by 2 mo after treatment. Imazapic suppressed new vegetative growth 3 mo after treatment compared with the nonmowed–nontreated control (16.1 cm of growth) and the mowed–nontreated control (21.1 cm) when applied with the rotary-wick applicator (8.5 cm) and broadcast sprayer (6.2 cm). However, differences in vegetative height primarily occurred when application placement equipment treatments were compared with nontreated vegetation as opposed to mowed–nontreated plants. Although mowed–nontreated and wet-blade–treated plots had more new vegetative growth, nonmowed–nontreated plots still consistently had the greatest vegetative height. Seedhead suppression ranged from 87 to 100% when compared with the nonmowed–nontreated control, with wet-blade treatments consistently providing the least-effective seedhead suppression. Overall, application placement equipment did not improve plant growth-regulator efficacy when compared with the foliar broadcast spray.

New hybrid bluegrass cultivars have been bred for increased heat and drought tolerance compared with traditional Kentucky bluegrass cultivars. Research was conducted to evaluate hybrid bluegrass tolerance and smooth crabgrass and goosegrass control with mesotrione and quinclorac during seeded establishment. Mesotrione applied as a single application 14, 28, or 42 d after emergence (DAE) injured hybrid bluegrass acceptably from 1 to 11% 7 d after treatment (DAT). A sequential mesotrione application at 0.14 kg/ha 28 DAE did not injure hybrid bluegrass greater than the initial 14 DAE application; however, a sequential application at 0.28 kg/ha 28 DAE injured hybrid bluegrass greater than the initial 14 DAE application. Three sequential mesotrione applications did not reduce hybrid bluegrass ground cover 63 DAE. Quinclorac applied singly at 1.68 kg/ha 14 DAE and sequentially at 0.84 kg/ha 14 and 28 DAE injured hybrid bluegrass that continued throughout the rating period resulting in decreased ground cover at 63 DAE. Quinclorac at 0.84 kg/ha plus mesotrione at 0.28 kg/ha injured hybrid bluegrass < 20% throughout the rating period but reduced ground cover 63 DAE. All quinclorac-containing treatments controlled smooth crabgrass ≥ 92%. All mesotrione sequential-application treatments controlled smooth crabgrass and goosegrass ≥ 87%. These data indicate that sequential mesotrione applications can be used for smooth crabgrass and goosegrass control during seeded hybrid bluegrass establishment. Quinclorac should be applied according to label recommendations at 0.84 kg/ha no earlier than 28 DAE.

Cogongrass is a highly invasive perennial grass that threatens agriculture, forestry, and native plant assemblages in many regions of the world. Cogongrass is a prolific seed producer, but the ecological importance of seeds as a vector of invasion has not been adequately addressed. Propagule pressure plays a key role in many successful invasions and the relative importance of propagule pressure across environmental gradients is an area of research that is quickly becoming important in understanding invasion success. The present study was conducted to test the effects of varying propagule density upon the ability of cogongrass seedlings to grow and establish across experimentally manipulated light and soil gradients. Seedlings growing in high-nutrient soil performed the best regardless of the amount of available light, but overall biomass was always greatest in high-light environments. Cogongrass showed a very strong trend in biomass allocation, with seedlings in reduced light environments partitioning more biomass to aboveground tissue. The data provided no evidence that initial propagule density affected the growth and establishment of cogongrass seedlings, but growth and biomass production were positively correlated with final seedling density.

The difficulty of monitoring growth parameters of climbing invasive plants subjected to different control options can be overcome by using standardized support structures (trellises). The utility of such support structures on aboveground biomass accumulation and fruit production was demonstrated using the invasive climber, bridal creeper in three invaded nature reserves near Perth in Western Australia. Mean above-ground plant biomass for plots provided with trellises ranged from 204 ± 38 g/m2 to 336 ± 31 g/m2, whereas it ranged from 66 ± 10 g/m2 to 118 ± 10 g/m2 in plots with no trellises. The mean number of fruits/m2 produced on shoots in plots provided with trellises ranged from 424 ± 159 to 3,787 ± 873 and was up to almost four orders of magnitude greater than the number of fruits produced on plants in plots with no trellis (ranging from 0 to 5.25 ± 7.9). The use of standardized trellises also showed that fruit volume and fruit seed number can vary significantly between sites. Standardized trellises have been installed at sites across Australia to assess the long-term impact of biological control agents introduced to manage bridal creeper.

Certified Crop Advisors of Arkansas and members of the Arkansas Crop Consultants Association were surveyed in Fall 2006 through direct mail to assess current weed management practices and needs in cotton from both a research and educational perspective. Consultants reported scouting 162,300 of the possible 473,700 ha of cotton grown in Arkansas. Collectively, glyphosate-resistant and enhanced glyphosate-resistant cultivars were reported grown on 98% of the cotton hectares. Ninety-five percent of the consultants believe the planting of enhanced glyphosate-resistant cultivars will increase over the next 5 yr. All consultants indicated a “moderate” to “high” level of concern with herbicide-resistant weeds in cotton, and 79% of the consultants suspect herbicide resistance in the fields they scout, predominately glyphosate-resistant horseweed. Horseweed, Palmer amaranth, and morningglories were the three most problematic weeds in cotton. A continued focus on resistant weed management was the most frequent research and educational request by consultants.

Certified Crop Advisors of Arkansas and members of the Arkansas Crop Consultants Association were surveyed in Fall 2006 through direct mail to assess current weed management practices and needs in rice from both a research and educational perspective. Consultants reported scouting 228.2 of the possible 567 thousand hectares (40%) of rice grown in Arkansas. Pre-emergence herbicides most often recommended were clomazone (93%) and quinclorac (40%). Propanil (55%) and quinclorac (47%) were the two most commonly recommended postemergence herbicides. Thirty-two percent of the consultants often recommend three or more herbicide applications per field. An average of 37% of the fields were believed to have “serious” or “very serious” weed infestations, and fields were scouted for weeds on average 11 times per growing season. Ninety-two percent of the consultants had “moderate” to “high” concerns with herbicide-resistant weeds. The perceived average additional expense associated with managing a resistant weed in rice was $65.60/ha. Propanil-resistant and quinclorac-resistant barnyardgrass were believed to be infesting 24 and 7% of the scouted rice hectares, respectively. Barnyardgrass was the most problematic weed of rice followed by red rice. Northern jointvetch and smartweeds were the two most problematic broadleaf weeds. The number one research need was improved broadleaf weed control. Respondents indicated that research and educational efforts should continue to focus on herbicide performance and development of economical weed control programs.

Advances in statistical software allow statistical methods for nonlinear regression analysis of dose-response curves to be carried out conveniently by non-statisticians. One such statistical software is the program R with the drc extension package. The drc package can: (1) simultaneously fit multiple dose-response curves; (2) compare curve parameters for significant differences; (3) calculate any point along the curve at the response level of interest, commonly known as an effective dose (e.g., ED30, ED50, ED90), and determine its significance; and (4) generate graphs for publications or presentations. We believe that the drc package has advantages that include: the ability to relatively simply and quickly compare multiple curves and select ED-levels easily along the curve with relevant statistics; the package is free of charge and does not require licensing fees, and the size of the package is only 70 MB. Therefore, our objectives are to: (1) provide a review of a few common issues in dose-response-curve fitting, and (2) facilitate the use of up-to-date statistical techniques for analysis of dose-response curves with this software. The methods described can be utilized to evaluate chemical and non-chemical weed control options. Benefits to the practitioners and academics are also presented.