Pecan trees subjected to different weed control and irrigation regimes from planting in 1986 through 1993 produced similar yields when irrigated (400 kg/ha, 3-yr avg) and not irrigated (320 kg/ha, 3-yr avg). Trees receiving total chemical weed control produced over five times more pecans (735 kg/ha, 3-yr avg) than weedy trees (131 kg/ha, 3-yr avg). Trees receiving disking produced more pecans when irrigated (677 kg/ha, 3-yr avg) than when not irrigated (339 kg/ha, 3-yr avg). Growth rate, expressed as increase in tree stem diameter, decreased for trees in all treatments once trees began bearing.

Studies were conducted for 12 wk from June 16 to September 8, 2003 and July 10 to October 4, 2004 with the objective of evaluating growth regulation, lateral regrowth, and injury of Tifway bermudagrass [Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy Tifway] in response to two GA-inhibiting plant growth regulators, trinexapac-ethyl and flurprimidol. Trinexapac-ethyl was applied alone at 0, 0.052, and 0.104 kg ai/ha and flurprimidol alone at 0, 0.14, and 0.28 kg ai/ ha, plus all combinations. Applications were made every 3 wk for the duration of the study. Tifway bermudagrass clipping yield was reduced 33% and 54% by trinexapac-ethyl at 0.104 kg/ha at 4 and 8 wk after initial treatment (WAIT), respectively. Flurprimidol at 0.28 kg/ha reduced clipping yield 49% 8 WAIT. Lateral regrowth was reduced 20% 2 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 26% 2 WAIT by flurprimidol at 0.28 kg/ha. Lateral regrowth was reduced 13% 4 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 15% 4 WAIT by flurprimidol at 0.28 kg/ha. Overall, acceptable injury (<30%) was observed with a trinexapac-ethyl and flurprimidol tank mixture; however, this evaluation did not indicate an advantage in growth regulation when using a tank mixture of these products, compared to using them alone.

The interaction of DPX-A7881 and clopyralid applied as tank mixtures was studied under controlled environment and field conditions on several commonly occurring weeds in canola. Control of wild mustard and wild buckwheat was not affected by mixing these herbicides. DPX-A7881 controlled wild mustard, and clopyralid controlled wild buckwheat independently of the other herbicide. However, redroot pigweed and common lambsquarters were controlled better with DPX-A7881 plus clopyralid than with either herbicide alone. The herbicides interacted in an additive to synergistic manner on redroot pigweed depending on the rate of each herbicide. DPX-A7881 and clopyralid interacted synergistically at all rates on common lambsquarters. Plant height, date of flowering, seed yield, and quality data all indicated that canola completely tolerated DPX-A7881 and clopyralid applied alone or in combination.

A glasshouse study was conducted on the Louisiana State University campus in Baton Rouge, LA, to evaluate the control of brook crowngrass, rice cutgrass, southern watergrass, and water paspalum. Florpyrauxifen-benzyl was applied at 30 g ai ha−1 to each grass species at the 3- to 4-leaf or 1- to 2-stolon stage of growth. Brook crowngrass treated with florpyrauxifen was controlled 71% at 21 d after treatment. Southern watergrass and water paspalum control did not exceed 56% and 36%, respectively, across all evaluations. Rice cutgrass treated with florpyrauxifen did not reach 15% control. Plants treated with florpyrauxifen, except rice cutgrass, displayed reduction in leaf number, stolon number, plant height, and plant fresh weight. These results indicate florpyrauxifen-benzyl can help manage a brook crowngrass infestation and suppress southern watergrass. However, florpyrauxifen-benzyl has little to no activity on water paspalum and rice cutgrass, and other management options should be employed if these weeds are present.

Pinoxaden is a POST acetyl coenzyme A carboxylase (ACCase) inhibitor in the phenylpyrazolin chemical family and is labelled for turfgrass use at broadcast rates of 35.5 to 71 g ai ha−1 and spot spray rates of 156 to 310 g ai ha−1. A greenhouse rate-response study was conducted to characterize the efficacy of pinoxaden against common grassy weeds. Weed species examined in this study were yellow foxtail, southern sandbur, annual bluegrass, roughstalk bluegrass, large crabgrass, dallisgrass, bahiagrass, goosegrass, and perennial ryegrass. Nonlinear regressions were modelled to determine visible injury rates (the application rate at which 50% of the weed species were injured and the 90% [I90] rate) and weight reduction rates (the application rate at which there was a 50% reduction in fresh weight and 90% reduction [WR90]) for each weed species. Only annual bluegrass, bahiagrass, and goosegrass had visible injury I90 values greater than the maximum labelled spot spray rate of 310 g ai ha−1. Annual bluegrass, bahiagrass, southern sandbur, and goosegrass all had WR90 values greater than the maximum labelled spot spray rate of 310 g ai ha−1. Results from this study indicate that the evaluated weed species can be ranked, according to visible injury I90 values, from most to least susceptible: perennial ryegrass > yellow foxtail > dallisgrass > large crabgrass > southern sandbur > roughstalk bluegrass > bahiagrass > goosegrass > annual bluegrass.

Giant miscanthus is under consideration as a biofuel crop in the United States; however, there is little information on weed management for the establishment and survival of this crop. Therefore, greenhouse and field studies using ornamental pots were conducted in summer 2011 at Tifton, GA, with the objective of screening potential PPI, PRE, and POST herbicides and herbicide combinations for giant miscanthus when establishing from vegetative rhizomes. For the POST treatments, giant miscanthus was established from rhizomes in 7.6-L containers in the field and treated with 27 POST herbicides to evaluate efficacy. Thifensulfuron, metsulfuron, tribenuron, chlorimuron, halosulfuron, rimsulfuron, cloransulam, pinoxaden, bentazon, and metribuzin did not significantly lower shoot height, reduce shoot dry weight, or increase injury compared with nontreated control (NTC) when evaluated at 4 wk after treatment. Nicosulfuron, trifloxysulfuron, sulfometuron, clodinafop, fluazifop, and pyrithiobac caused the greatest injury, reduced plant height, and reduced dry weights compared with the NTC. Sethoxydim, diclofop, flumioxazin, imazamox, imazapic, and imazethapyr decreased plant heights or resulted in increased injury. PPI and PRE treatments included 21 herbicides and herbicide combinations applied at two rates. Results indicated that most treatments containing atrazine, metribuzin, pendimethalin, acetochlor, metolachlor, and mesotrione did not injure or stunt growth; however, EPTC at 4.5 kg ai ha−1 significantly reduced height and dry weight and oxadiazon resulted in greater injury compared with NTC at both rates. These results indicate that PPI, PRE, and POST herbicides can be utilized for establishment of giant miscanthus from vegetative rhizomes. Considering the invasive potential of giant miscanthus, several POST herbicides evaluated in this study such as fluazifop, pyrithiobac, and sulfometuron may be viable options to control this species if it becomes invasive.

It is well established that soybean that does not contain the dicamba-resistant (DR) trait is highly sensitive to off-target exposure to dicamba. However, there is limited information on the effect of low doses of dicamba plus glyphosate mixtures on dicamba-sensitive soybean—a mixture likely to be used on a vast acreage of dicamba/glyphosate-resistant soybean. The objective of this research was to examine leaf and pod malformation, along with height and yield effects, when dicamba, glyphosate, or a mixture of the two was applied to soybean sensitive to both dicamba and glyphosate at sublethal doses. Field applications were made at three growth stages (R1, R3, and R5) at multiple locations. Two glyphosate rates (1/64 and 1/256 of the labeled rate of 870 g ae ha−1) and two dicamba rates (1/64 and 1/256 of the labeled rate of 560 g ae ha−1) were used. Adding glyphosate to dicamba increased leaf malformation by 6% more than dicamba alone when applied at the R1 soybean growth stage. After R3 applications, pod malformation was 10% greater in treatments containing dicamba and glyphosate than dicamba alone. Applications at R5 showed minimal leaf and pod malformation. Seed from field trials was planted in the greenhouse to evaluate the offspring. The number of offspring plants showing dicamba-like symptomology was not increased with the addition of glyphosate to dicamba. Overall, injury to offspring was similar in dicamba alone and dicamba plus glyphosate treatments; however, the number of plants injured increased when parent plants were exposed to sublethal doses of dicamba at R3 and R5 compared with R1 growth-stage exposure. Vigor was reduced in dicamba-containing treatments, but not glyphosate-alone treatments. Glyphosate addition to dicamba had no effect on vigor of soybean offspring. Although there is increased injury to parent plants when glyphosate is added to dicamba, this research demonstrates that glyphosate does not contribute to the negative effects of dicamba on soybean offspring.

In 1753 Linneaus named the genus Potentilla in his Species Plantarum. The common name five finger is used frequently for this group of plants. The genus, in the rose family (Rosaceae), is composed of about 500 north temperate species (50 in North America, 75 European species) of mostly boreal herbs and shrubs. Indeed, Potentilla extends far into arctic regions. However, a few species are south temperate. And although less common, some species are also found in alpine and high mountain regions of the tropics and South America; P. anserinoides Lehm. is a New Zealand native.

Dicamba and 2,4-D systems control many problematic weeds; however, drift to susceptible crops can be a concern in diverse production areas. Glufosinate-based systems are an alternative, but current recommended rates of glufosinate can result in variable control. Research was conducted in 2017 and 2018 to investigate the optimum time interval between sequential glufosinate applications and determine if the addition of glyphosate with glufosinate is beneficial for controlling Palmer amaranth and annual grasses in cotton. The interval between sequential applications (1, 3, 5, 7, 10, or 14 d or no second spray) was the whole plot and herbicide option (glufosinate or glufosinate plus glyphosate) was the subplot. Combined over herbicides, Palmer amaranth 15- to 20-cm tall (at four locations) was controlled 98% to 99% with sequential intervals of 1 to 7 d compared with 70% to 88% with intervals of 10 or 14 d. Lowest biomass weight and population densities were noted with 1- to 7-d intervals. Large crabgrass 15- to 20-cm tall (at five locations) was controlled 93% to 98% with glufosinate applications 3- to 7-d apart as compared with 76% to 81% with applications 10- to 14-d apart. Lowest biomass weights were observed with 1- to 7-d intervals. When glufosinate controlled grass less than 93%, adding glyphosate was beneficial. Neither interval between sequential applications nor herbicide option influenced cotton yield. Shorter time intervals between sequential application and including glyphosate can improve the effectiveness of a glufosinate-based system in managing Palmer amaranth and large crabgrass.

Field experiments were conducted in the summers of 1988 and 1989 to evaluate sericea lespedeza control with POST herbicides. Triclopyr, picloram, 2,4-D, metsulfuron, dicamba, and selected herbicide mixtures were evaluated in 1988 and 1989. Clopyralid was evaluated in 1988 and fluroxypyr in 1989. Triclopyr at 0.56 and 1.12 kg ha–1 controlled sericea lespedeza both years. Fluroxypyr at 0.56 kg ha–1 also controlled sericea lespedeza. Control with picloram and metsulfuron was variable. Other treatments evaluated did not control sericea lespedeza.

Field trials were conducted over two spring seasons (2005 and 2006) to investigate the interference between American black nightshade and watermelon in polyethylene-mulched and nonmulched (bare ground) trials. Competition studies were performed with watermelon at 1 plant/m in-row and American black nightshade grown at 0, 2, 4, 6, and 8 plants/m2 in-row. Watermelon yield reductions started to plateau at only 2 American black nightshade plants/m2. Yield reduction was 80, 89, 96, and 98% and 54, 67, 81, and 85% at 2, 4, 6, and 8 American black nightshade plants/m2 in mulched watermelon production in 2005 and 2006, respectively. When watermelon was grown on bare ground, yield reduction was 100% at 2 American black nightshade plants/m2 in 2005 and 68, 81, 89, and 93% at 2, 4, 6, and 8 American black nightshade plants/m2 in 2006, respectively. Watermelon fruit numbers were reduced due to American black nightshade interference, but no significant differences in individual fruit weight were observed.

Field experiments were conducted in 1996 and 1997 to evaluate weed control and dry bean response to mechanical tillage and herbicide treatments. Herbicide treatments were EPTC plus ethalfluralin, dimethenamid, and imazethapyr plus bentazon. Herbicides were applied alone or combined with rotary hoeing and in-row cultivation. Differences in dry bean yields between years were due to differences in weed density. Weed species included redroot pigweed, common lambsquarters, hairy nightshade, wild proso millet, and green foxtail. Weed density in the untreated check plots at the end of the growing season was 35 plants/m2 in 1996 and 134 plants/m2 in 1997. Dry bean stands were not reduced by rotary hoeing, in-row cultivation, and herbicides in 1996, but in-row cultivation reduced dry bean populations 27% compared to the hand-weeded check in 1997. In-row cultivation and rotary hoeing provided similar weed control in both years. At low weed densities, either mechanical tillage or herbicides alone were effective in suppressing weeds, whereas at higher densities, herbicides combined with mechanical tillage were required for effective control.

In 1983 and 1984, 20 commercial soybean [Glycine max (L.) Merr.] cultivars were field tested for their response to fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine], metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-l,2,4-triazin-5(4H)-one], and vernoiate [S-propyl dipropylcarbamothioate]. Recommended rates for the herbicides were 1.1, 0.4, and 2.8 kg ai/ha, respectively. Each herbicide was applied at recommended (lx), 2x, and 4x rates in both years with an 8x rate added in 1984. Plant height, vigor, and injury were used to determine herbicide effects. Differences existed among cultivars, herbicides, and rates. Increased herbicide rates generally resulted in reduced plant height and vigor and increased plant injury. Cultivars tolerant to the three herbicides included Cumberland, Essex, FFR 560, NAPB 420, and Pixie.

Field experiments were conducted near Scottsbluff, NE, to evaluate the selectivity of sequential POST applications of ethofumesate and triflusulfuron for weed control in sugarbeet. When applied alone ethofumesate and triflusulfuron reduced common lambsquarters, hairy nightshade, and redroot pigweed density while triflusulfuron also reduced kochia density compared with an untreated control. Combining ethofumesate with desmedipham plus phenmedipham increased sugarbeet injury compared with desmedipham plus phenmedipham. Combining triflusulfuron with desmedipham plus phenmedipham increased kochia control but did not increase sugarbeet injury over that obtained with desmedipham plus phenmedipham. Weed control and sugarbeet injury from herbicides generally were unaffected by application in 97 or 182 L/ha of water carrier. However, herbicide control of hairy nightshade in 1993 was greater with 97 than 182 L/ha of water carrier.

Field experiments were conducted in Michigan, Minnesota, and Wisconsin to evaluate injurious interactions between nicosulfuron herbicide applied POST and nine insecticides applied at planting on ‘Pioneer 3751’ field corn in 1991. Insecticides were applied in-furrow, T-band, and surface band at planting. Corn injury from nicosulfuron and terbufos applications was more severe in Wisconsin than in Michigan. No corn injury was observed in Minnesota. Terbufos 15% ai granule (15G) or 20% ai controlled release granule (20CR) increased nicosulfuron injury to corn in Wisconsin. Nicosulfuron at 35 g ai/ha caused the greatest vigor reduction following terbufos 15G, intermediate vigor reduction following terbufos 20CR, phorate 20G, or phorate 20CR, and the least vigor reduction following fonofos, chlorpyrifos, chlorethoxyfos, tefluthrin, or carbofuran in Wisconsin.

Johnsongrass control in fallowed sugarcane fields was evaluated with glyphosate and the graminicides quizalofop, fluazifop, and clethodim applied in soybean compared with nonsoybean tillage and glyphosate programs. Glyphosate was applied to glyphosate-resistant soybean as a single early postemergence (EPOST) treatment around 30 d after planting (DAP) at rates of 840, 1,120, or 2,240 g ai/ha; as sequential treatments EPOST and late postemergence (LPOST) around 60 DAP at 560 followed by (fb) 560 or 1,120 fb 1,120 g/ha; or as a single LPOST treatment at 2,240 g/ha. Quizalofop at 77 g ai/ha, fluazifop at 420 g ai/ha, and clethodim at 280 g ai/ha were also evaluated as single EPOST treatments. In 1996 johnsongrass control 7 d after EPOST treatment (DAT) was at least 90% for glyphosate treatments but control was 73 to 77% for the graminicides. In 1997 johnsongrass control 7 DAT was at least 82% for all herbicide treatments. Excellent johnsongrass control approximately 50 DAT was achieved both years with all the glyphosate and graminicide treatments. In the nonsoybean fallow weed control programs where plots were tilled twice or three times fb one or two glyphosate applications, complete control of johnsongrass was obtained both years. In 1996 when glyphosate was applied EPOST or EPOST fb LPOST, soybean yields were equivalent and averaged 3.3 times that of the single LPOST glyphosate application. Soybean yields where the graminicides were used and where glyphosate was applied as a single LPOST treatment were no greater than the nontreated control. Economic analysis on the basis of soybean yield data and variable costs of herbicides, seed, field application, seedbed preparation, tillage, labor, fuel, repairs, and custom harvest expense in 1996 showed a positive net return only for glyphosate applied EPOST at 840 g/ha ($99.82/ha) or 1,120 g/ha ($46.94/ha) and for glyphosate applied at 560 g/ha EPOST fb LPOST ($10.41/ha). Although showing a negative net return, glyphosate applied EPOST at 2,240 g/ha ($−8.32/ha) or EPOST fb LPOST at 1,120 g/ha ($−50.97/ha), the loss was less than that for nonsoybean fallow tillage and glyphosate programs ($−155.70/ha and $−157.78/ha). In 1997, when soybean was not harvested because of environmental conditions, variable costs exceeded those of the nonsoybean programs, indicating that planting soybean strictly as a cover crop would not be economically advantageous. Sugarcane growth and yield the year following the fallow programs was not negatively affected by production of soybean regardless of herbicide program.

There is a high potential for inadvertent herbicide injury to crops in western Canada on an annual basis because of the diversity of crops grown in close proximity to each other, although accurate data regarding the annual number of injury incidents is not available. A field study was conducted at two locations in southern Manitoba, Canada, in 2001 and 2002, to investigate the effects of a range of dosages of MCPA ester, glyphosate, and thifensulfuron:tribenuron (2:1) applied to the seedling growth stage of conventional (nongenetically engineered) canola and white bean on subsequent shoot dry matter and crop yield. Similar to other studies that utilized sublethal herbicide dosages, results between site-years were variable, particularly for crop yield. Where possible, a nonlinear log-logistic model was fitted to the data. Generally, canola was more sensitive than white bean to the herbicides used in this study. Based on the fitted regression equations and recorded mean values for canola, 10% of the commercial herbicide dosage normally applied in other (possibly adjacent) crops caused greater than 10% canola yield loss for 9 of 12 unique combinations of herbicide-site-year. For white bean, 10% of the commercial herbicide dosage caused yield losses greater than 10% for only 4 of 13 unique combinations of herbicide-site-year. Spray drift is probably the most common source of inadvertent application of herbicide to sensitive crops; generally, only a fraction of the herbicide dosage applied on an adjacent crop drifts off-target. The results of this study indicate that for any of the three herbicides investigated on canola and white bean, it is difficult to accurately predict eventual crop yield loss based on early season sublethal herbicide injury symptoms due to site-year variability and the potential for crop recovery and compensatory growth. This response was particularly true for white bean in this study.

Three experiments were conducted in Lewiston, NC, from 1999 through 2002 to evaluate the influence of various application timings of flumioxazin preplant (PP) and postemergence-directed spray (PDS) on cotton injury. In experiment 1, flumioxazin was evaluated in a reduced-tillage system at 71, 105, or 140 g ai/ha in mixture with glyphosate, applied at 28, 14, or 7 d before planting (DBP), followed by irrigation at cotton emergence. Flumioxazin applied PP at any rate and irrigated at emergence injured cotton less than 7% at 2 wk after emergence (WAE) and less than 6% 5 WAE. In experiment 2, flumioxazin was evaluated in a conventional-tillage system at 71 or 105 g/ha as a PDS treatment applied to dry soil, wet soil, and dry soil irrigated immediately after application when cotton was 20 to 30 cm height. Cotton treated with flumioxazin PDS at either rate applied to dry soil, wet soil, or dry soil followed immediately by irrigation was not injured. In the third experiment, flumioxazin at 71 g/ha alone or in mixture with glyphosate at 1.12 g/ha was applied at 30, 21, 14, and 0 DBP in a conventional-tillage system. Flumioxazin applied alone or in mixture with glyphosate applied at any time did not injure cotton. In all experiments, cotton lint yields were not influenced by herbicide treatment.

Laboratory studies were conducted to determine if electrolyte leakage from either leaf tissue, germinating seeds, or excised roots correlated with previously established soil-applied field response of soybean cultivars and target weeds to sulfentrazone. Sulfentrazone-induced electrolyte leakage from leaf tissue of coffee senna (sensitive), sicklepod (tolerant), and soybean cultivars ‘Asgrow 6785’ and ‘Carver’ (sensitive) and ‘Stonewall’ and ‘DPL 3606’ (tolerant) was monitored over time. Electrolyte leakage from leaf tissues, caused by 25 ppm (65 μM) sulfentrazone, agreed directly with the known response of these weeds, but response of the four soybean cultivars was equivalent. Furthermore, sulfentrazone-induced electrolyte leakage from leaf tissue of Asgrow 6785 and Stonewall was not affected by sulfentrazone concentration as high as 100 ppm (258 μM) nor by light intensity (4 and 120 μmol/m2/s photosynthetically active radiation). For germinating seeds, sulfentrazone-induced electrolyte leakage was also independent of soybean cultivar. In contrast, electrolyte leakage from excised roots of germinal soybean seedlings did concur directly with the previously established cultivar sensitivity to soil-applied sulfentrazone. Results indicate that electrolyte leakage from excised roots of soybean germinal seedlings can be used to assess cultivar sensitivity to soil-applied sulfentrazone.