Rice is one of the staple food crops of India, and Karnataka is one of the major rice-producing states. The primary method of rice establishment in Karnataka is transplanting, but farmers are opting to shift to direct-seeding of rice. Weed management is critical for realizing optimal yield of direct-seeded rice (DSR). The objective of this review was to synthesize the published literature on weeds and weed management in rice in Karnataka, identify improved weed-management technologies for delivery to farmers, and suggest research needs. Some 98 weed species are reported to be associated with rice in Karnataka. Weed control to date in Karnataka has mostly been based on herbicides. Hand-weeding was found to be effective in all methods of rice establishment. However, it is time-consuming, tedious, and costly because labor is becoming scarce and unavailable, and labor wages are higher. Several PRE and POST herbicides that were effective in other Asian countries were also found to be effective in managing weeds in rice established by different methods in Karnataka. Bensulfuron plus pretilachlor and pyrazosulfuron in aerobic rice and pendimethalin, thiobencarb, bispyribac-sodium, cyhalofop, fenoxaprop plus chlorimuron plus metsulfuron, and fenoxaprop plus ethoxysulfuron in dry-DSR were found effective in managing weeds. In wet-DSR, butachlor plus safener and pretilachlor plus safener were effective. Thiobencarb, pendimethalin, pretilachlor, azimsulfuron plus metsulfuron, bispyribac-sodium, butachlor, cinosulfuron, oxadiazon, and quinclorac were found promising for weed management in transplanted rice. Integration of herbicides with hand-weeding or intercultivation was found to be effective in rice established by different methods. Options that were found economical in managing weeds varied across the different rice-establishment methods. The need for developing location-specific, sustainable, integrated weed management and extension of available technologies for the farming community in Karnataka is emphasized.

In recent years injury has been reported in numerous Tennessee corn fields treated with an organophosphate (OP) insecticide and either a mesotrione- or tembotrione-based herbicide premix. Research was conducted with the objective to determine if corn treated with an in-furrow application of chlorpyrifos or a foliar application of chlorpyrifos or bifenthrin, or a combination of in-furrow and foliar treatment, would be more predisposed to injury when either a premix of S-metolachlor, mesotrione, and glyphosate (meso premix) or a premix of tembotrione plus thiencarbazone (tembo premix) was applied. The main effects of insecticide or herbicide, the two-way interaction of insecticide by herbicide, and the three-way interaction of herbicide by insecticide by application type of insecticide were all significant for injury as well as yield. When chlorpyrifos was used both in-furrow and foliarly on corn treated with the tembo premix, injury was increased to 56% and yield was reduced 58% compared with corn that had not been treated with that insecticide. This use pattern of chlorpyrifos utilized in-furrow followed by chlorpyrifos applied foliarly with the tembo premix essentially doubled the injury (29 to 56%) and increased yield loss from 41% where chlorpyrifos was only utilized foliarly to 49% when chlorpyrifos was applied in-furrow and foliarly. Corn injury was negligible (< 6%) and yield was similar where the meso premix was examined in combination of both types of insecticide applications. This study clearly demonstrated the phytotoxic interaction between these two herbicide premixes and the OP insecticide chlorpyrifos. Therefore, growers need to be mindful of which herbicides are utilized when OP insecticides are used for insect management.

Field experiments were conducted in 2011 through 2013 at the MSU Southern Agricultural Research Center near Huntley, MT, to evaluate the effectiveness of various PRE and POST herbicide programs for kochia control in the absence of a crop. PRE herbicides labeled for corn, grain sorghum, soybean, wheat/barley, and/or in chemical fallow were applied at recommended field-use rates. Acetochlor + atrazine, S-metolachlor + atrazine + mesotrione, and sulfentrazone applied PRE provided ≥91% control of kochia at 12 wk after treatment (WAT). Metribuzin, metribuzin + linuron, and pyroxasulfone + atrazine PRE provided 82% control at 12 WAT. PRE control with acetochlor + flumetsulam + clopyralid, pyroxasulfone alone, and saflufenacil + 2,4-D was ≤23% at 12 WAT. Paraquat + atrazine, paraquat + linuron, and paraquat + metribuzin controlled kochia ≥98% at 5 WAT. POST control with bromoxynil + fluroxypyr, paraquat, tembotrione + atrazine, and topramezone + atrazine treatments averaged 84% at 5 WAT, and did not differ from glyphosate. Control with POST-applied bromoxynil + pyrasulfotole, dicamba, diflufenzopyr + dicamba + 2,4-D, saflufenacil, saflufenacil + 2,4-D, saflufenacil + linuron was 67 to 78% at 5 WAT. Because of the presence of kochia resistant to acetolactate synthase-inhibiting herbicides at the test site, cloransulam-methyl was not a viable option for kochia control. In a separate greenhouse study, kochia accessions showed differential response to the POST herbicides (labeled for corn or soybean) tested. Tembotrione + atrazine, topramezone + atrazine, lactofen, or fomesafen effectively controlled the glyphosate-resistant kochia accession tested. Growers should utilize these effective PRE- or POST-applied herbicide premixes or tank mixtures (multiple modes of action) to control herbicide-resistant kochia accessions in the field. PRE herbicides with 8 wk of soil-residual activity on kochia would be acceptable if crop competition were present; however, a follow-up herbicide application may be needed to obtain season-long kochia control in the absence of crop competition.

Soybean cyst nematode (SCN) is a major soybean yield–limiting disease in the United States. Henbit, a winter annual species common to no-till fields in the midwestern United States, is known to act as an alternative host for SCN. A simulation was performed to estimate how likely SCN was to reproduce on henbit roots during a 30-yr period in two important soybean production areas of Nebraska. Simulations were conducted using published information on henbit seedling emergence, SCN reproduction on henbit roots, and SCN response to soil temperature. Results indicate that SCN would be able to complete one generation on henbit roots under Nebraska conditions. The SCN reproductive cycle was not likely to be completed before the winter in south central Nebraska, but one SCN generation was predicted to be completed in the fall in 2 out of 30 simulation years (7% likelihood) in southeast Nebraska. Based on our predictions, to reduce the chances of SCN population build-up in the absence of its main host (soybean), weed management in fields infested with both henbit and SCN should be completed after crop harvest in the fall when most henbit seedlings have emerged and are growing but the SCN developing on henbit roots have not yet achieved full maturity in Nebraska.

Turfgrass injury from triazines has limited the use of photosystem II (PS II) inhibitors for weed control in seashore paspalum. Amicarbazone is a new PS II inhibitor with potential safety in seashore paspalum, but the effects of application timing on turf tolerance has received limited investigation. Field experiments were conducted in Griffin, GA to evaluate the tolerance of ‘Sea Isle 1’ seashore paspalum to amicarbazone applications in winter, spring, and summer. Seashore paspalum had minimal injury (< 5%) from amicarbazone treatments (98, 196, and 392 g ai ha−1) applied for annual bluegrass control in winter and spring. By 6 wk after treatment (WAT), amicarbazone at 392 g ha−1 provided 78 and 90% annual bluegrass control in 2013 and 2014, respectively, and was similar to pronamide at 1,680 g ai ha−1. Amicarbazone at 196 g ha−1 provided 71% control of annual bluegrass in 2014, but control was poor (< 70%) in 2013. Sequential amicarbazone applications at 98 g ha−1 provided poor control in both years by 6 WAT. From six amicarbazone rates (up to 984 g ha−1) applied in summer, seashore paspalum required 510 and < 123 g ha−1 for 20% turfgrass injury (I20) and 20% clipping reduction (CR20), respectively, whereas I20 and CR20 measured > 984 g ha−1 for ‘Tifway’ bermudagrass. Overall, amicarbazone may be safely applied to seashore paspalum in winter, spring, and summer at rates and regimens evaluated. However, seashore paspalum may exhibit shoot growth inhibition up to 4 WAT, suggesting that end users should be cautious when using amicarbazone during active growth in summer.

With the frequency of glyphosate-resistant waterhemp increasing throughout the Midwest, the identification of resistant populations has become important for managing this species. However, high-throughput screening for glyphosate resistance in the greenhouse is tedious and inefficient. Research was conducted to document the occurrence of glyphosate-resistant waterhemp throughout the state of Illinois, and to determine whether a molecular assay for 5-enolypyruvyl-shikimate-3-phosphate synthase (EPSPS) gene amplification can be used as an alternative means to detect resistant populations. Populations throughout the state of Illinois were collected in 2010 and screened for glyphosate resistance using a whole-plant assay in a greenhouse, and survivors were examined for EPSPS gene amplification. Of 80 populations investigated, 22 were glyphosate resistant based on the greenhouse screen, and gene amplification was identified in 20 (91%) of the resistant populations. Although there are multiple mechanisms for glyphosate resistance in waterhemp, a molecular test for EPSPS gene amplification provides a rapid alternative for identification of glyphosate resistance in most populations.

Winter sowing of lentil results in higher yields than a spring-sown crop. However, when lentil is winter-sown, the critical period of weed control is extended and might require sequential herbicide management strategies to obtain maximum yields. The efficacy of POST alone or soil applied followed by (fb) POST herbicides or hand weeding were evaluated in 2002 and 2003. Trifluralin (PPI) or pendimethalin (PRE) were applied at planting, and pyridate or oxyfluorfen were applied POST at the three- to four-leaf stage of lentil. The lowest level of weed biomass was recorded with all treatments, except pyridate alone in both years, pendimethalin PRE fb pyridate in 2002, and oxyfluorfen in 2003. Application of pyridate or oxyfluorfen POST alone resulted in lower yields. In 2002, trifluralin PPI or pendimethalin PRE fb one hand weeding or pendimethalin fb pyridate resulted in yields similar to the weed-free treatment. In 2003, yields were similar to the weed-free treatment, except pyridate or oxyfluorfen alone and trifluralin PPI fb oxyfluorfen. Weed species observed in the present study required sequential management to achieve both effective control and maximum lentil yield.

PRE herbicides are generally less effective in conservation farming systems because of high levels of crop residue. However, performance can be improved if the herbicides are applied with a high carrier volume. This research investigated the interaction of carrier volume and row spacing or height of crop residue on the control of rigid ryegrass with trifluralin, at Cunderdin and Wongan Hills Western Australia. To create plots with varying residue row spacing in 2011, wheat was seeded in 2010 using a narrow row spacing (25 or 22 cm at Cunderdin and Wongan Hills), wide spacing (50 or 44 cm), or not planted to wheat. Narrow or wide row spacing or no crop plots had an average residue biomass of 4480, 3560, and 2430 kg ha−1 at Cunderdin and 1690, 1910, and 1030 kg ha−1 at Wongan Hills. To vary residue height, the wheat was harvested to produce tall, medium, or short crop residue (22, 13, and 5 cm at Cunderdin and 27, 22, and 17 cm at Wongan Hills). Rigid ryegrass seeds were broadcast onto each site in 2011 and trifluralin was sprayed using 50, 75, or 100 L ha−1 carrier volume (directly prior to seeding). Increased carrier volume increased spray coverage at both sites (average cover of 9, 15, and 26% at 50, 75, and 100 L ha−1), leading to improved control of rigid ryegrass (68, 75, and 82% control at Cunderdin and 23, 41, and 68% control at Wongan Hills). Reduced crop residue height or increased row spacing led to reduced rigid ryegrass density at Cunderdin but had no impact at Wongan Hills. Therefore, carrier volume has a more consistent impact on the performance of trifluralin than crop residue row spacing or height.

Soybean planting has occurred earlier in the Midwestern United States in recent years; however, earlier planting subjects the crop to longer durations of weed interference. This may change the optimum timing of POST glyphosate applications, or increase the need for residual herbicides applied PRE to optimize yield. A field study was conducted in 2012 and 2013 near Arlington, WI to determine the effect of planting date, residual herbicide use, and POST glyphosate timing on weed control and soybean yield. Planting dates were late April, mid-May, and early June. A PRE application of sulfentrazone plus cloransulam was applied to half the plots following each planting date. Glyphosate was applied POST to all plots at the V1, V2, V4, or R1 soybean growth stage. Planting date and glyphosate timing did not affect soybean yield in this study. However, averaged across years, planting dates, and POST glyphosate timings, yield increased from 3,280 to 3,500 kg ha−1 when a PRE herbicide with residual soil activity was used. In POST-only treatments, delaying the planting date to June decreased weed density at POST application timing from 127 to 5 plants m−2 (96%) and from 205 to 42 plants m−2 (80%) in 2012 and 2013, respectively. Where a PRE was used, total weed density at POST application timing was always less within planting date, and also declined from early to late planting date 26 to 3 plants m−2 (89%) and 23 to 6 plants m−2 (74%) in 2012 and 2013, respectively. In conclusion, both PRE herbicide use and delayed soybean planting were effective strategies to reduce the number of in-crop weeds exposed to POST glyphosate and should be considered as strategies to reduce the number of weeds exposed to POST herbicides for resistance management.

Glyphosate-resistant common waterhemp is a difficult-to-control annual broadleaf weed that has become a serious management challenge for growers in Nebraska and other states in the United States. The objectives of this study were to confirm glyphosate-resistant common waterhemp in Nebraska by quantifying level of resistance in a dose-response study, and to determine the sensitivity and efficacy of POST soybean herbicides for controlling suspected glyphosate-resistant common waterhemp biotypes. Seeds of suspected glyphosate-resistant common waterhemp biotypes were collected from seven eastern Nebraska counties. Greenhouse dose-response experiments were conducted to evaluate the response of common waterhemp biotypes to nine rates of glyphosate (0 to 16×). Common waterhemp biotypes were 3- to 39-fold resistant to glyphosate depending on the biotype being investigated and the susceptible biotype used for comparison. Results of the POST soybean herbicides efficacy experiment suggested that glyphosate-resistant biotypes, except a biotype from Pawnee County, had reduced sensitivity to acetolactate synthase (ALS)–inhibiting herbicides (chlorimuron-ethyl, imazamox, imazaquin, imazethapyr, and thifensulfuron-methyl). Glufosinate and protoporphyrinogen oxidase (PPO)–inhibiting herbicides (acifluorfen, fluthiacet-methyl, fomesafen, and lactofen) provided ≥ 80% control of glyphosate-resistant common waterhemp at 21 d after treatment (DAT). This study confirmed the first occurrence of glyphosate-resistant common waterhemp in Nebraska, and also revealed reduced sensitivity to ALS-inhibiting herbicides in most of the biotypes tested in this study.

Occurrence of glyphosate-resistant (GR) canola volunteers in GR sugar beet is a management concern for growers in the Northern Great Plains. Field experiments were conducted at the Southern Agricultural Research Center near Huntley, MT, in 2011 and 2012 to evaluate effective herbicide programs to control volunteer GR canola in GR sugar beet. Single POST application of triflusulfuron methyl alone at the two-leaf stage of sugar beet was more effective at 35 compared with 17.5 g ai ha−1. However, rate differences were not evident when triflusulfuron methyl was applied as a sequential POST (two-leaf followed by [fb] six-leaf stage of sugar beet) program (17.5 fb 17.5 or 35 fb 35 g ha−1). Volunteer GR canola plants in the sequential POST triflusulfuron methyl–containing treatments produced little biomass (11 to 15% of nontreated plots) but a significant amount of seeds (160 to 661 seeds m−2). Ethofumesate (4,200 g ai ha−1) PRE followed by sequential POST triflusulfuron methyl (17.5 or 35 g ha−1) provided effective control (94 to 98% at 30 d after treatment [DAT]), biomass reduction (97%), and seed prevention of volunteer GR canola. There was no additional advantage of adding either desmedipham + phenmedipham + ethofumesate premix (44.7 g ha−1) or ethofumesate (140 g ha−1) to the sequential POST triflusulfuron methyl–only treatments. The sequential POST ethofumesate-only (140 fb 140 g ha−1) treatment provided poor volunteer GR canola control at 30 DAT, and the noncontrolled plants produced 6,361 seeds m−2, which was comparable to the nontreated control (7,593 seeds m−2). Sequential POST triflusulfuron methyl–containing treatments reduced GR sugar beet root and sucrose yields to 18 and 20%, respectively. Consistent with GR canola control, sugar beet root and sucrose yields were highest (95 and 91% of hand-weeded plots, respectively) when the sequential POST triflusulfuron methyl–containing treatments were preceded by ethofumesate (4,200 g ha−1) PRE. Growers should utilize these effective herbicide programs to control volunteer GR canola in GR sugar beet. Because of high canola seed production potential, as evident from this research, control efforts should be aimed at preventing seed bank replenishment of the GR canola volunteers.

Fresh market spinach has limited herbicides available and weed management in this crop is dependent on hand-weeding. Phenmedipham is a POST herbicide registered for use on spinach grown for processing or for seed, but not fresh market spinach. This study evaluates the potential use of phenmedipham alone and in combination with cycloate for weed control in fresh spinach production. Greenhouse and field studies were conducted in 2013 using two spinach varieties known to have low and high tolerance to phenmedipham. The greenhouse studies showed that phenmedipham at 270 and 550 g ai ha−1 was safe to spinach when applied at the four-leaf stage for the low- and high-tolerance varieties, respectively. Phenmedipham was evaluated alone (550 g ha−1) and applied to the four-leaf stage in two varieties. Subsequently, a second experiment evaluated cycloate (1,700 g ha−1) followed by (fb) phenmedipham at several rates (90, 180, and 270 g ha−1). Phenmedipham alone (550 g ha−1) did not result in crop injury when applied to four-leaf spinach; however, the weed control was not better than cycloate alone. When applied as a sequential treatment following cycloate, all phenmedipham rates were safe to spinach and significantly improved weed control compared to cycloate alone. Cycloate fb phenmedipham at 270 g ha−1 provided 87% weed control relative to cycloate alone. This level of weed control was similar to the cycloate plus hand-weeding treatment, which provided 98% control. Results here show that cycloate fb phenmedipham improves weed control compared to cycloate alone, and has the potential to reduce hand-weeding costs in the fresh spinach production.

Flumioxazin is commonly used in nursery production for PRE weed control. Container nursery producers are of the opinion that the granular formulation is less effective than the sprayable formulation. Under the hypothesis that the granular formulation may require more water for activation, an experiment was conducted to evaluate the interaction of flumioxazin formulation, rate, and activation moisture for PRE control of spotted spurge in a pine-bark substrate. Experiment consisted of a factorial arrangement of four experimental variables; flumioxazin formulation (granular and spray), and flumioxazin rate (0.28 and 0.42 kg ai ha−1), substrate moisture level at the time of application (dry, medium, and wet), and after-application irrigation level (a single irrigation at 0.6, 1.3, 2.5, and 5.1 cm). Treated pots were seeded with spotted spurge 2 d after the herbicide application, which was 1 d after the first irrigation. Control as indicated by spotted spurge counts and fresh weight was influenced only by flumioxazin rate and formulation. The sprayable formulation provided excellent control regardless of rate. Granular formulation was generally less effective, and additional activation moisture did not improve efficacy. Further studies were conducted with the granular formulation to determine the maximum separation distance between the spotted spurge seed and herbicide prills at which control is possible. Individual prills and spotted spurge seeds were placed on media surface at progressively increasing separation distances. Nonlinear regression of seedling survival data revealed that ≥99% control required a prill–seed separation of ≤5.2 mm. This prill–seed separation requirement is only marginally obtained with the current registered rate, i.e., 0.42 kg ai ha−1 or 168 kg product ha−1. The relationship between control and prill–seed separation distance cannot be manipulated by additional activation moisture. Inadequate contact between the spotted spurge seeds and the flumoioxazin-containing prills is likely the sole cause of inadequate control.

Poison ivy is a virulent weed that is frequently treated with herbicides. Dicamba, 2,4-D, and two fixed-ratio tank mixtures of dicamba plus 2,4-D were evaluated across a series of rates for poison ivy control. Objective was to test whether tank mixtures were more effective than either herbicide applied alone. Dicamba alone, 2,4-D alone, a 1 : 3, and a 3 : 1 ratio (by weight) mixture of dicamba plus 2,4-D, respectively, were applied at eight rates to 2-yr-old, container-grown poison ivy plants. The eight rates ranged from 0.036 to 1.79 kg ae ha−1, which, in terms of phytotoxicity, generally ranged from none to death. Percentage of control was determined from plant fresh-weight reduction relative to a nontreated control and was determined at 1 and 4 mo after treatment (MAT). Rates required for 95% control at 1 MAT and for control of regrowth at 4 MAT and the cost of those treatments were determined for the dicamba and 2,4-D applied alone and in the two mixtures. At the 1-MAT evaluation, 2,4-D alone was more cost effective than either dicamba alone or the two mixtures. By the 4-MAT evaluation, however, which followed clipping at 3 MAT, dicamba alone was more cost effective than either mixture. The 2,4-D alone failed to provide 95% control at the 4 MAT evaluation, even at the highest rate evaluated (1.79 kg ha−1). Response curves for the two mixtures were equivalent to the response curves of the components applied alone at the 1 MAT evaluation and fell between the response curves of the components at the 4 MAT evaluation. Hence, 2,4-D plus dicamba mixtures were neither antagonistic nor synergistic. Results indicate that dicamba applied alone is far more effective than 2,4-D is for control of established and perennial poison ivy, assuming the intent is to obtain control with a single, one-time application.

Soft rush is a perennial plant found in or along water ditches on cranberry farms that can impede drainage as well as water movement within production areas, and can easily spread into production areas. Established tussocks are not substantially affected by chemical controls and proximity to water resources limits herbicide application. The efficacy of flame cultivation (FC) with hand-held tools is being evaluated for efficacy to manage perennial weeds in cranberry production. Two separate studies were conducted on a Massachusetts cranberry farm to evaluate the effectiveness of FC for rush control. A single exposure was made in June with an open flame (OF), infrared (IR), or infrared with a metal spike (IRS) FC tool at four different exposure durations. Stem number, biomass, and percentage flowering stems decreased linearly for plants treated with the IR torch. For plants treated with OF, the number of stems decreased linearly, while biomass and percentage flowering stems decreased quadratically as exposure duration increased. Although IR reduced rush growth, OF required shorter exposure durations (8 s versus 60 s) to achieve similar results. The IRS tool was not effective for controlling rushes. A second study compared the efficacy of a single clipping event, a single, medium exposure of OF, OF immediately followed by (fb) clipping, or clipping immediately fb OF. All treatments reduced the mean number of stems, biomass and percentage of flowering stems per tussock compared to the nontreated control but the clipping fb FC treatment reduced the number of stems more than clipping alone. Future experiments on FC use for rush control in cranberry production should explore potential improvement with multiple treatments within a single season as well as repeated annual applications of treatments.

Intensive cultivation in organic peanut is partially effective, but in-row weed control remains problematic. In an attempt to improve in-row weed control, irrigated trials were conducted from 2011 to 2013 near Ty Ty, GA to determine the feasibility of early-season cultivation perpendicular to row direction using a tine weeder when integrated with other weed-control practices. Combinations of perpendicular cultivation (cultivation perpendicular to row direction), parallel cultivation (cultivation in the same direction of the rows), and banded applications of herbicides derived from natural sources were compared. Perpendicular cultivation improved overall weed control and peanut yield (two years of three), but this benefit was independent of weed control from any form of parallel cultivation. Additionally, tractor tire tracks from perpendicular cultivation across the rows repeatedly crushed peanut seedlings. Parallel cultivation with the tine weeder was generally more effective than parallel cultivation with sweeps, particularly for southern crabgrass and Texas millet. Herbicides derived from natural products were inconsistent in controlling dicot weeds, ineffective in controlling annual grasses, and did not protect peanut yield from weed interference.

Interest in the cultivation of bioenergy feedstocks has increased the need for information in this rapidly developing sector of agriculture. Many fast-growing, large-statured perennial grasses have been selected because of their high biomass production potential, competitive nature, and ability to tolerate marginal growing conditions. However, weed pressure in the establishment phase can be detrimental to crop yield. Weed control is one of the most costly and resource-intensive aspects of bioenergy crop establishment. Unfortunately, little information exists on practical weed management techniques for the majority of these new crops. The tolerance of switchgrass, big bluestem, reed canarygrass, sorghum, giant reed, eulaliagrass, and giant miscanthus (sterile and seeded) to 22 PRE and 22 POST herbicides were evaluated. Plants were grown in the greenhouse and evaluated for injury, height, and aboveground biomass after 5 or 7 wk for PRE and POST applications, respectively. PRE and POST application of 2,4-D, bentazon, bromoxynil, carfentrazone, dicamba, halosulfuron, and topramezone did not significantly injure any species. Giant miscanthus was more tolerant to PRE herbicides when established from rhizomes compared with seed establishment. Supporting previous research, all eulaliagrass and switchgrass cultivars demonstrated comparable tolerance to PRE application of all 22 herbicides. With the information gained in this study a suite of herbicides may have potential for use in bioenergy crops; however, they should be tested on larger-scale field trials over multiple growing seasons to validate initial findings.

Buckhorn plantain is a perennial weed in turfgrass and efficacy of POST herbicides is often inconsistent for control in spring. Indaziflam is a cellulose biosynthesis inhibitor used for PRE control of annual weeds in turf and applications have shown to be injurious to established buckhorn plantain. The objectives of this research were to evaluate (1) effects of indaziflam application rate and placement on buckhorn plantain injury; (2) effects of tank-mixing indaziflam with POST herbicides for buckhorn plantain control; and (3) physiological effects of indaziflam on absorption and translocation of 14C-2,4-D in buckhorn plantain. In greenhouse experiments, indaziflam reduced buckhorn plantain shoot mass 61 to 75% from the nontreated at 4 wk after treatment (WAT) and hierarchical rank of application placements were: foliar + soil ≥ soil ≥ foliar. Differences in biomass reduction from application rates (27.5 and 55 g ai ha−1) were not detected. In field experiments, indaziflam at 55 g ha−1 controlled buckhorn plantain 34% at 9 WAT but enhanced the speed of control from all herbicides tested in tank mixtures. Exclusive applications of 2,4-D or 2,4-D + dicamba + MCPP provided poor control (< 70%) of buckhorn plantain at 9 WAT, but tank mixtures with indaziflam provided 81 and 98% control, respectively. Fluroxypyr and simazine alone controlled buckhorn plantain < 38% but tank mixtures with indaziflam enhanced control more than twice as much from exclusive applications. Tank-mixing indaziflam with metsulfuron did not improve control from metsulfuron alone after 9 wk. Bermudagrass injury was not detected from any treatment. In laboratory experiments, 14C-2,4-D absorption and translocation in buckhorn plantain was similar with or without indaziflam tank mixtures at 72 and 168 h after treatment. Overall, indaziflam may improve buckhorn plantain control from POST herbicides by providing additive phytotoxicity in tank mixtures in spring.

Glyphosate-resistant (GR) weeds are most challenging for growers to control in cotton in the midsouth region of the United States. As a result, growers in these states are transitioning from a glyphosate-based system to a glufosinate-based system. A field study was conducted in 2010 and 2011 in Georgia, North Carolina, and Tennessee to determine the effect of repeated glufosinate applications to WideStrike cotton applied at various application timings. One to three glufosinate applications at 594 g ai ha−1 were applied to cotton at the two-leaf, seven-leaf, bloom, or 2 wk after bloom stages. Visual estimates of crop injury were evaluated after each application, in addition to crop height, development, and yield. Crop injury after each glufosinate application typically ranged from 3 to 11%, with higher injury observed where multiple glufosinate applications were made. Crop height differences were noted after the bloom and 2 wk after bloom applications. Treatments that had one, two, or three glufosinate applications had reduced crop height when compared with the weed-free control. Node above cracked boll ratings also indicated that glufosinate treatments may have stressed the cotton. Ultimately, yield was reduced where three glufosinate treatments were applied to WideStrike cotton. In addition, one glufosinate application at the bloom stage or two glufosinate applications at the bloom and 2 wk after bloom stages reduced yield when compared with the weed-free control. Although it is a legal application, growers should use caution when applying glufosinate to WideStrike cotton because the manufacturer of glufosinate and the manufacturer of WideStrike cotton do not recommend this application. However, where GR Palmer amaranth is present, these applications may be necessary.

Rhizoma et Radix Notopterygii is often used as a traditional medicine in China. In our recent work, we found that the ethanol crude extract of Rhizoma et Radix Notopterygii could reduce phytotoxicity of acetochlor on rice. The crude extract of Rhizoma et Radix Notopterygii was isolated and purified by activity-guided fractionation. Two coumarins, isopimpinellin and 5-methoxypsoralen (5-MOP) were identified, and their bioactivity was tested in a growth chamber. The results showed that the two coumarins increased herbicide tolerance of rice shoots, and 5-MOP demonstrated better protection than isopimpinellin. The treatment of 5-MOP at 50 g ai ha−1 recovered the shoot height of rice from 42.6% (treated with acetochlor only) to 81.6% of the control treated without acetochlor, whereas the phytocidal activity of acetochlor on barnyardgrass was not impaired by 5-MOP. Further study suggested that 5-MOP increases herbicide tolerance of rice by enhancing the glutathione S-transferase level of activity in rice. Our findings suggest that isopimpinellin and 5-MOP have the potential to be applied as safeners for rice.