Corn Herbicides Research Articles

Efficacy of Preplant Corn and Soybean Herbicides on Star-of-Bethlehem (Ornithogalum umbellatum) in No-Till Crop Production

Field research was conducted to evaluate the efficacy of preplant herbicides commonly used in no-till corn and soybean production and to determine the efficacy of three application timings in the spring for star-of-Bethlehem bulb management. A single, preplant application of herbicide treatments that included flumioxazin, sulfentrazone, or paraquat resulted in 91 to 97% control of star-of-Bethlehem at 14 d after treatment (DAT). Star-of-Bethlehem control from atrazine and metribuzin was moderate (70 to 75%) at the Marion location but poor (< 20%) at Murphysboro. Regardless of the initial foliar control at 14 DAT from treatments included in the corn and soybean herbicide screen, only applications containing paraquat resulted in extensive control (75 to 86%) of star-of-Bethlehem foliar regrowth by 1 yr after treatment. Star-of-Bethlehem was most responsive to herbicide applications in mid-March in southern Illinois when compared with applications made March 1 and April 11. The mid-March application timing corresponded to the vegetative reproductive stage, approximately 3 wk prior to flowering. The average density of star-of-Bethlehem bulbs in nontreated plots occupied 7.9% of the field soil volume in the upper 7.6 cm of the soil profile. Spring applications of paraquat (repeated 2 yr consecutively) reduced bulb density in the soil by 88%, compared with 5% or less bulb reduction for consecutive applications of glyphosate or 2,4-D ester applied alone. Overall, paraquat and paraquat tank mixtures provided the most effective and consistent control of star-of-Bethlehem foliage and underground bulbs, which is paramount for long-term management of this invasive species.

Response of selected glyphosate-resistant broadleaved weeds to premix of fluthiacet-methyl and mesotrione (Solstice™) applied at two growth stages

Ganie, Z. A., Stratman, G. and Jhala, A. J. 2015. Response of selected glyphosate-resistant broadleaved weeds to premix of fluthiacet-methyl and mesotrione (Solstice™) applied at two growth stages. Can. J. Plant Sci. 95: 861–869. A premix of fluthiacet-methyl and mesotrione (1:17.5 ratio) has recently been registered for post-emergence (POST) broadleaf weed control in corn. The objective of this study was to determine the response of glyphosate-resistant common waterhemp, giant ragweed, and kochia to a premix of fluthiacet-methyl and mesotrione when applied to 10- and 20-cm-tall plants. Greenhouse dose response studies were conducted and log-logistic models were used to determine how the response varies between the weed species at two growth stages under various rates ranging from 21.8 to 218.5 g a.i. ha−1 (0.25× to 2.5×). The effective rate required to achieve >90% control and shoot biomass reduction varied depending on the weed species and growth stage. The rates required for 90% control (ED90) of 10-cm-tall glyphosate-resistant common waterhemp, giant ragweed, and kochia were 78, 251, and 17 g a.i. ha−1, respectively, compared with 144, 489, and 79,349 g a.i. ha−1, respectively, for 20-cm-tall plants at 21 d after treatment (DAT). Based on visual control estimates at ED90 level, glyphosate-resistant common waterhemp was the most sensitive at both growth stages; kochia was sensitive at 10-cm height, while giant ragweed was the least sensitive at both growth stages. Irrespective of weed species or growth stage, the ED90 values calculated on the basis of shoot biomass reduction were mostly higher compared with visual control estimates. It is concluded that premix of fluthiacet-methyl plus mesotrione can be potentially used as a POST herbicide in corn for controlling glyphosate-resistant common waterhemp and kochia (≤ 10 cm tall) at the labeled rate (87 g a.i. ha−1).

Integrating Cover Crops and POST Herbicides for Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Control in Corn

Field experiments were conducted in 2013 and 2014 in Jackson, TN, to evaluate the efficacy of integrating cover crops and POST herbicides in corn to control glyphosate-resistant (GR) Palmer amaranth. Crimson clover and hairy vetch were planted in the fall and accumulated greater than 1,600 kg ha−1aboveground biomass by time of termination. Crimson clover and hairy vetch provided 62% and 58% Palmer amaranth control 14 d before application, respectively. POST herbicide treatments of glyphosate +S-metolachlor + mesotrione + atrazine, thiencarbazone-methyl + tembotrione + atrazine, and glyphosate + atrazine were applied when Palmer amaranth reached 15 cm tall. The herbicide treatments provided greater than 95% control of Palmer amaranth 28 d after application. In addition to Palmer amaranth suppression, corn was taller at V5 and V7 following a hairy vetch cover crop. Hairy vetch and crimson clover residues provided early season weed suppression because of biomass accumulation. Palmer amaranth in the nontreated control plots reached 15 cm 4 and 3 d ahead of the cover-treated plots in 2013 and 2014, respectively. This could potentially increase POST herbicide-application flexibility for producers. Results of this trial also suggest that cover crops alone are not a means of season-long control of GR Palmer amaranth. From a herbicide resistance-management perspective, the integration of cover crops with herbicide mixtures that incorporate multiple sites of action should aid in mitigating the further selection of herbicide resistance in Palmer amaranth.

Effect of Biostimulants Added to Postemergence Herbicides in Corn, Oats and Winter Wheat

There is limited information available on the effect of biostimulants such as Crop Booster or RR SoyBooster on corn, oats and winter wheat under Ontario environmental conditions. A total of 37 field experiments were conducted in corn, oats and winter wheat at two locations (Ridgetown and Exeter, Ontario, Canada) to evaluate the effect of Crop Booster or RR SoyBooster on crop injury, weed control and yield. The addition of Crop Booster to glyphosate did not affect weed control or corn yield except at 4 weeks after herbicide application (WAA) when control of pigweed species was increased by 1% and at 4 and 8 WAA when control of common lambsquarters was reduced by 1%. The addition of RR SoyBooster to glyphosate did not affect crop injury, weed control or corn yield. The addition of Crop Booster to glyphosate + topramezone + atrazine did not affect crop injury, weed control or corn yield except at 4 WAA when control of common ragweed was reduced by 1%. The tank mix of Crop Booster with glyphosate + thiencarbazone-methyl did not affect crop injury, weed control or corn yield except at 4 WAA when control of green foxtail and annual grasses were reduced by 2% and 1%, respectively. The addition of Crop Booster to bromoxynil/ MCPA had no significant effect on crop injury, weed control or yield of oats or winter wheat.

Winter Annual Weed Response to Nitrogen Sources and Application Timings prior to a Burndown Corn Herbicide

Autumn and early preplant N applications, sources, and placement may affect winter annual weed growth. Field research evaluated (1) the effect of different nitrogen sources in autumn and early preplant on total winter annual weed growth (2006–2010), and (2) strip-till and broadcast no-till N applied in autumn and early preplant on henbit (Lamium amplexicauleL.) growth (2008–2010) prior to a burndown herbicide application. Total winter annual weed biomass was greater than the nontreated control when applying certain N sources in autumn or early preplant for no-till corn. Anhydrous ammonia had the lowest average weed density (95 weeds m−2), though results were inconsistent over the years. Winter annual weed biomass was lowest (43 g m−2) when applying 32% urea ammonium nitrate in autumn and was similar to applying anhydrous ammonia in autumn or early preplant and the nontreated control. Henbit biomass was 28% greater when applying N in the autumn compared to an early preplant application timing. Nitrogen placement along with associated tillage with strip-till placement was important in reducing henbit biomass. Nitrogen source selection, application timing, and placement affected the impact of N on winter annual weed growth and should be considered when recommending a burndown herbicide application timing.

Evaluation of bio-fertilizer effect on selective corn herbicides efficiency to control of Chenopodium album and Amaranthus retroflexus

Evaluation of bio-fertilizer effect on selective corn herbicides efficiency to control of Chenopodium album and Amaranthus retroflexus

Critical source areas for herbicides can change location depending on rain events

During rain events, herbicides can be transported from their point of application to surface waters, where they may harm aquatic organisms. Since the spatial variability of herbicide losses to streams can be large, the identification of critical source areas could help to target mitigation measures efficiently to those locations where they reduce herbicide pollution the most. We performed a controlled herbicide application on wheat (isoproturon) and corn fields (atrazine, S-metolachlor and sulcotrione) in an agricultural head-water catchment (about 1km2) in the Swiss Plateau to investigate the spatial variability of herbicide losses. We performed spatially distributed discharge measurements and high-resolution water sampling during rain events after herbicide application to determine herbicide loads and loss rates for individual fields. The dry weather conditions after the wheat herbicide application resulted in a very low isoproturon loss rate (0.005% of the applied amount). In contrast, the corn herbicide application was followed by several rain events with varying intensities and magnitudes causing loss rates of 0.26, 0.16 and 0.26% for atrazine, S-metolachlor and sulcotrione, respectively. The spatial differences in loss rates between fields were about a factor of three in most events. However, the spatial loss pattern varied between events implying that being a critical source area is not a temporally stable field property. No correlations were observed with several field characteristics (connectivity of the fields to the stream, the tendency for topsoil saturation, field-specific herbicide dissipation rates and sorption affinities). However, the data suggest that critical source areas may depend on the type of rain event because infiltration and saturation-excess runoff affects different parts of the catchment.

Confirmation and Control of Triazine and 4-Hydroxyphenylpyruvate Dioxygenase-Inhibiting Herbicide-Resistant Palmer Amaranth (Amaranthus palmeri) in Nebraska

Palmer amaranth is a difficult-to-control broadleaf weed that infests corn and soybean fields in south-central and southwestern Nebraska and several other states in the United States. The objectives of this research were to confirm triazine and 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide-resistant Palmer amaranth in Nebraska and to determine sensitivity and efficacy of POST-applied corn herbicides for control of resistant and susceptible Palmer amaranth biotypes. Seeds from a putative HPPD-resistant Palmer amaranth biotype from Fillmore County, NE were collected from a seed corn production field in fall 2010. The response of Palmer amaranth biotypes to 12 rates (0 to 12×) of mesotrione, tembotrione, topramezone, and atrazine was evaluated in a dose–response bioassay in a greenhouse. On the basis of the values at the 90% effective dose (ED90) level, the analysis showed a 4- to 23-fold resistance depending upon the type of HPPD-inhibiting herbicide being investigated and susceptible biotype used for comparison. This biotype also had a 9- to 14-fold level of resistance to atrazine applied POST. Results of a POST-applied herbicide efficacy study suggested a synergistic interaction between atrazine and HPPD-inhibiting herbicides that resulted in > 90% control of all Palmer amaranth biotypes. The resistant biotype had a reduced sensitivity to acetolactate synthase inhibiting herbicides (halosulfuron and primisulfuron), a photosystem-II inhibitor (bromoxynil), and a protoporphyrinogen oxidase inhibitor (fluthiacet-methyl). Palmer amaranth biotypes were effectively controlled (≥ 90%) with glyphosate, glufosinate, and dicamba, whereas 2,4-D ester provided 81 to 83% control of the resistant biotype and > 90% control of both susceptible biotypes.

Ionic liquid-based foam flotation followed by solid phase extraction to determine triazine herbicides in corn

Ionic liquid-based foam flotation followed by solid phase extraction was developed for extraction of eight triazine herbicides, including cyanazine, metribuzin, desmetryn, secbumeton, terbumeton, terbuthylazine, dimethametryn and dipropetryn in corn samples. When the extraction was completed, the analytes were separated from the sample matrix by foam flotation and introduced into the solid phase extraction cartridge. The separation and concentration of target analytes were performed simultaneously. The analytes eluted from the solid phase extraction cartridge were determined by high performance liquid chromatography. The effects of experimental parameters of extraction and flotation were examined. Under the optimized experimental conditions, a good linearity was obtained in the range of 2.50-150 µg/kg. The detection limits of the triazine herbicides were in the range of 0.74-1.62 µg/kg. The present method was successfully applied to the analysis of corn samples. The recoveries ranged from 85.9% to 104.0% and the relative standard deviations were lower than 5.6%.

Efficacy of POST glyphosate applications in combination with other POST herbicides in glyphosate-resistant corn (Zea mays L.)

The use of glyphosate-resistant corn has facilitated a shift from a reliance on preemergence residual herbicides to postemergence (POST) herbicides, and in some cases exclusively glyphosate. Glyphosate is a non-selective herbicide that is relatively slow-acting, which may allow weeds to continue to compete with corn after application and potentially decrease crop yield. The addition of several POST corn herbicides, with some residual control, to an early-season glyphosate application was examined to determine if the tankmix combination would improve the speed of weed control compared to glyphosate applied alone. Seven field trials were conducted over three years (2009, 2010 and 2011) near Ridgetown and Exeter, Ontario. The control of common ragweed was improved 3 days after application (DAA) with three POST glyphosate tankmixes compared to glyphosate alone. However control was still less than 55%. Depending on the weed species examined, at 28 DAA two of the glyphosate tankmix treatments tested provided better common ragweed, common lambsquarters, or green foxtail control than glyphosate alone. Treatments providing better weed control at 28 DAA also typically decreased weed density compared to glyphosate alone.

Responses of an HPPD Inhibitor-Resistant Waterhemp (Amaranthus tuberculatus) Population to Soil-Residual Herbicides

Field experiments were conducted in 2010 and 2011 at a Mclean County, IL seed corn production field where resistance to foliar-applied 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors was confirmed in waterhemp. Corn herbicides were applied to the soil at 1 and 2 times (1× and 2×, respectively) the recommended field use rate, while soybean herbicides were applied only at 1× the recommended rate. Waterhemp control and density were determined 30 and 60 d after treatment (DAT). In corn, 1× rates of mesotrione, safened and unsafened isoxaflutole formulations, atrazine, andS-metolachlor provided less than 70% control 30 DAT, while control with acetochlor was greater than 80%. One and 2× rates of acetochlor and 2× rates of mesotrione and unsafened isoxaflutole provided the greatest reduction of waterhemp density across years. At 30 DAT in soybean, sulfentrazone, flumioxazin, metribuzin, and pyroxasulfone provided the highest levels of waterhemp control (84 to 92%), as well as the greatest reduction in waterhemp density both years. A dose–response experiment with soil-applied mesotrione was performed under controlled greenhouse conditions using three waterhemp populations: MCR15 (seed collected from the McLean Co. site), NH41 (progeny obtained from the McLean Co. population by an additional generation of mesotrione selection in the greenhouse), and a sensitive (S). Emergence counts 21 DAT revealed higher seedling survival of MCR15 and NH41 at mesotrione rates of 105 g ha−1or less compared with the sensitive control. Resistant-to-sensitive (R/S) ratios for NH41 and MCR15 were 12.7 and 8.8, respectively. Field results indicate the McLean Co. waterhemp population demonstrates reduced sensitivity to soil-applied HPPD-inhibiting herbicides. This is supported by greenhouse results that demonstrate reduced sensitivity to mesotrione in MCR15 and NH41.

Efficacy of Various Corn Herbicides Applied Preplant Incorporated and Preemergence

Field studies were conducted in central Missouri and central Kansas to evaluate the crop tolerance and efficacy of various combinations of atrazine, flufenacet + isoxaflutole, flumetsulam + clopyralid, isoxaflutole, andS-metolachlor applied PPI or PRE in conventional-till corn. Application technique did not influence crop injury in Kansas. In Missouri, greater crop injury was observed with treatments containing isoxaflutole when applied PPI vs. PRE. Application technique influenced giant foxtail, ivyleaf morningglory, large crabgrass, Palmer amaranth, and common waterhemp control. In dry years, control of these weeds was usually either same or greater with PPI than it was with PRE treatments. In years with average to above average precipitation, isoxaflutole provided greater control as a PRE application than as a PPI application. Palmer amaranth and common waterhemp control was usually greater with atrazine, isoxaflutole, andS-metolachlor applied PRE than it was applied PPI. Differences in control of all weeds between PPI and PRE applications were less obvious with two or three herbicides compared with treatments with a single herbicide. In general, the corn yield was greater with most of the treatments having two, three, or four herbicides than it was with treatments having a single herbicide, which was due to better weed control with the tank-mixtreatments.

Determinants of Atrazine Contamination in the Homes of Commercial Pesticide Applicators Across Time

Twenty-nine commercial pesticide applicator households in eastern Iowa were enrolled to investigate in-home contamination of atrazine, the most commonly used corn herbicide in the Unites States. From each home, four vacuum dust samples were collected during atrazine application season (Visit 1) and again 6 months later during winter months (Visit 2). Samples were taken from the following locations: primary entryway for pesticide applicator, living room, master bedroom, and kitchen. The applicator completed an atrazine handling log and household questionnaire with spouse. Of the 230 dust samples, only 2 were below the level of detection, 2 ng of atrazine per gram (ng/g) of fine dust (dust particle size 5–150 μm). Dust levels were standardized to chemical loading. During application season the entryway (2.68 ng/cm2) and kitchen (0.47 ng/cm2) had the highest geometric mean atrazine chemical loading. The entryway chemical loading during Visit 2 was the second highest aggregate (0.55 ng/cm2). Aggregate concentrations were significantly higher at Visit 1 compared with Visit 2 when paired by location (p≤0.02). Analysis showed that job (application, mixing/loading, or both) was not associated with in-home atrazine contamination. Linear regression showed a strong positive association between atrazine handling (number of acres applied with atrazine, number of days atrazine handled, and pounds of atrazine handled) and aggregate dust chemical loading from both visits (p = 0.06, 0.03, and 0.10, respectively). Frequency of vacuuming was inversely associated with Visit 2 concentrations (p = 0.10) and showed a weaker association with Visit 1 (p = 0.30). Removing shoes outside the home was associated with lower atrazine chemical loading (p = 0.03), and applicators changing work clothes in the master bedroom had significantly increased atrazine chemical loading in master bedrooms (p = 0.01). Changes in hygiene practices for commercial pesticide applicators could significantly reduce atrazine and, likely, other pesticide contaminations in the home.

Precipitation Influences Pre- and Post-Emergence Herbicide Efficacy in Corn

Selecting a preemergence (PRE) and postemergence (POST) herbicide program that has the greatest efficacy can be difficult for corn producers and is highly dependent on weed spectrum. Weather conditions before and after herbicide application can further complicate decisions because they influence herbicide efficacy. Eleven field trials were conducted at three locations in Southwestern Ontario from 2003 to 2006, to determine the most effective PRE and POST corn herbicides for weed control. The most abundant weed species across all locations were redroot pigweed (Amaranthus retroflexus L.), common ragweed (Ambrosia artemisiifolia L.), common lambsquarters (Chenopodium album L.), and green foxtail (Setaria viridis (L.) Beauv.). Nine PRE herbicide treatments and eleven POST (applied at the 3-4 leaf stage of corn) herbicide treatments were tested. Results from this study suggest that the timing and amount of precipitation influence herbicide efficacy. For example, precipitation levels 0-17 mm within seven days after herbicide application (PRE or POST) provided unacceptable weed control in treatments that included atrazine, dimethenamidp, isoxa-flutole/atrazine or S-metolachlor/benoxacor. Cumulative precipitation during the 14 days after PRE application that exceeded the monthly average (by at least 64%) reduced Setaria viridis control with pendimethalin. This study demonstrates that a better understanding of how environmental conditions, especially precipitation affect herbicide efficacy, need to be considered by growers when selecting a corn herbicide program to reduce the possibility of weed control failure.

Significance of Atrazine as a Tank-Mix Partner with Tembotrione

Manufacturers of several POST corn herbicides recommend tank-mixing their herbicides with atrazine to improve performance; however, future regulatory changes may place greater restrictions on atrazine use and limit its availability to growers. Our research objectives were to quantify the effects of tank-mixing atrazine with tembotrione compared to tembotrione alone on (1) weed control, (2) variability in weed control, and (3) sweet corn yield components and yield variability. Field studies were conducted for 2 yr each in Illinois, Oregon, Washington, and Ontario, Canada. Tembotrione at 31 g ha−1 was applied alone and with atrazine at 370 g ha−1 POST at the four- to five-collar stage of corn. The predominant weed species observed in the experiment were common to corn production, including large crabgrass, wild-proso millet, common lambsquarters, and velvetleaf. For nearly every weed species and species group, the addition of atrazine improved tembotrione performance by increasing mean levels of weed control 3 to 45% at 2 wk after treatment. Adding atrazine reduced variation (i.e., standard deviation) in control of the weed community by 45%. Sweet corn ear number and ear mass were 9 and 13% higher, respectively, and less variable when atrazine was applied with tembotrione, compared to tembotrione alone. Additional restrictions or the complete loss of atrazine for use in corn will necessitate major changes in sweet corn weed management systems.

Development of a Method for the Simultaneous Determination of Six Sulfonylurea Herbicides in Wheat, Rice, and Corn by Liquid Chromatography–Tandem Mass Spectrometry

A sensitive and reliable method was developed and validated for trace determination of sulfonylurea herbicides residues in cereals (wheat, rice, and corn) by liquid chromatography-tandem mass spectrometry. The selected analytes were ethoxysulfuron, ethametsulfuron-methyl, bensulfuron-methyl, chlorimuron-ethyl, pyrazosulfuron-ethyl, and cyclosulfamuron. In this work, the extraction procedure was performed by using a mixture solvent of phosphate buffer (pH 9.5)/acetonitrile (8:2, v/v) as the extraction solvent and then was cleaned up by using Spe-ed C18/18% SPE cartridges, providing good recoveries for all of the tested analytes and with no matrix effects affecting method accuracy. The limits of detection for the studied analytes in cereal samples were between 0.043 and 0.23 μg kg(-1), and the limits of quantification were between 0.14 and 0.77 μg kg(-1), lower in all cases than the maximum residue limits permitted by the European Union for this kind of food. The developed methodology has demonstrated its suitability for the monitoring of these residues in cereal samples with high sensitivity, precision, and satisfactory recoveries.

The effect of residual corn herbicides on injury and yield of soybean seeded in the same season

Soltani, N., Mashhadi, R. H., Mesgaran, M. B., Cowbrough, M., Tardif, F. J., Chandler, K., Swanton, C. J. and Sikkema, P. H. 2011. The effect of residual corn herbicides on soybean injury and yield seeded in the same season. Can. J. Plant Sci. 91: 571–576. In rare situations, poor stands of corn are removed and reseeded to soybean later in the spring, even though residual corn herbicides have already been applied. Nine field studies were conducted over a 3-yr period (2005 to 2007) at four locations in Ontario, Canada, to determine the minimum interval for re-seeding to soybean following the application of residual corn herbicides. Five commonly used residual corn herbicide premixes or tankmixes were applied 6, 4, 2 or 0 wk before soybean seeding. The level of injury generally increased as the interval between herbicide application and soybean seeding decreased. Isoxaflutole plus atrazine caused as much as 28% injury and decreased plant stand, biomass and yield as much as 7, 49 and 42%, respectively. S-met...

The effect of residual corn herbicides on injury and yield of soybean seeded in the same season

Soltani, N., Mashhadi, R. H., Mesgaran, M. B., Cowbrough, M., Tardif, F. J., Chandler, K., Swanton, C. J. and Sikkema, P. H. 2011. The effect of residual corn herbicides on soybean injury and yield seeded in the same season. Can. J. Plant Sci. 91: 571-576. In rare situations, poor stands of corn are removed and reseeded to soybean later in the spring, even though residual corn herbicides have already been applied. Nine field studies were conducted over a 3-yr period (2005 to 2007) at four locations in Ontario, Canada, to determine the minimum interval for re-seeding to soybean following the application of residual corn herbicides. Five commonly used residual corn herbicide premixes or tankmixes were applied 6, 4, 2 or 0 wk before soybean seeding. The level of injury generally increased as the interval between herbicide application and soybean seeding decreased. Isoxaflutole plus atrazine caused as much as 28% injury and decreased plant stand, biomass and yield as much as 7, 49 and 42%, respectively. S-met...

Molecularly imprinted polymer coated on stainless steel fiber for solid-phase microextraction of chloroacetanilide herbicides in soybean and corn

A molecularly imprinted polymer (MIP) with metolachlor as template was firstly coated on stainless steel fiber through chemical bonding strategy to solve the fragility problem of silica fiber substrate for solid-phase microextraction. The surface pretreatment of stainless steel fiber and the polymerization conditions were investigated systematically to enhance the preparation feasibility and MIP coating performance, and then a porous and highly cross-linked MIP coating with 14.8-μm thickness was obtained with over 200 times re-usability which was supported by non-fragile stainless steel fiber adoption. The MIP coating possessed specific selectivities to metolachlor, its metabolites and other chloroacetanilide herbicides with the factors of 1.1–4.6. Good extraction capacities of metolachlor, propisochlor and butachlor were found with MIP coating under quick adsorption and desorption kinetics, and the detection limits of 3.0, 9.6 and 38 μg L −1 were achieved, respectively. Moreover, the MIP-coated stainless steel fiber was evaluated for trace metolachlor, propisochlor and butachlor extraction in the spiked soybean and corn samples, and the enrichment factors of 54–60, 27–31 and 15–20 were obtained, respectively.

Genetic Factors Influencing Adverse Effects of Mesotrione and Nicosulfuron on Sweet Corn Yield

Sensitivity to certain P450‐metabolized herbicides in corn (Zea mays L.) is largely conditioned by a single cytochrome P450 (CYP) gene. Little to no research has been done to evaluate the effect of CYP genotype on sweet corn yield. Yield of 23 sweet corn hybrids of known CYP genotype was evaluated in 2007, 2008, and 2009 following postemergence applications of mesotrione, an hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor, or nicosulfuron, an acetolactate synthase (ALS) inhibitor, at two growth stages. Mesotrione and nicosulfuron were evaluated in separate experiments. Treatments included herbicide application during the V3 to V5 or V5 to V7 growth stages and a nontreated control. Crop injury, measured 7 d after treatment (DAT), ranged from 0 to 87% for mesotrione and 0 to 54% for nicosulfuron among CYP genotypes. Injury from both mesotrione and nicosulfuron was most severe following application during V3 to V5 growth stages on hybrids with mutant (i.e., nonfunctional) cyp alleles. Only hybrids homozygous for mutant cyp alleles (i.e., cypcyp) suffered yield losses from mesotrione, ranging from 9 to 40%. These hybrids were not evaluated for nicosulfuron because applications of ALS‐inhibiting herbicides kill cypcyp hybrids. Nicosulfuron reduced the yield of CYPcyp hybrids only; whereas mesotrione did not. Yield losses from nicosulfuron ranged from 9 to 35% among CYPcyp hybrids and were associated with moderate to severe loss of kernel rows (i.e., ear pinching). Yield of CYPCYP hybrids was not affected by mesotrione or nicosulfuron.