Herbicide Injury Research Articles

Effect of postemergence fomesafen application on common milkweed (Asclepias syriaca) growth and utilization by monarchs (Danaus plexippus)

Field experiments were conducted to investigate impacts of herbicide injury to common milkweed (Asclepias syriaca L.) on oviposition preference of monarch butterflies (Danaus plexippus Linnaeus). Common milkweed seedlings were transplanted in patches containing five plants spaced 25 cm apart in a no-till soybean field shortly after soybean planting in 2016. Herbicide treatments included an untreated control and 0.14 kg ha−1 fomesafen plus 0.5% crop oil concentrate applied postemergence. The experiment was repeated in the same area in 2017 by planting soybean no-till prior to common milkweed emergence. Common milkweed leaves displayed chlorosis and necrotic lesions five days after fomesafen application during both years. Two weeks following application many leaves damaged by fomesafen dehisced, and plants averaged an injury rating of 3.4 (visual scale of 1 = healthy and 5 = dead). Leaves emerging from the apical meristem following fomesafen application appeared normal, and four weeks after application injury ratings decreased to an average of 2.6. Dry weight of common milkweed ten weeks after application was not affected by fomesafen in either year. Common milkweed plants were examined for monarch eggs and larval instars weekly from May to August. In 2016, patches averaged 0.8 eggs, whereas in 2017 patches averaged 45.2 eggs. Fomesafen did not affect oviposition preference by monarch butterflies in either year. Larval instars on the milkweed patches were recorded throughout 2017. Presence and survival of instars were not affected by fomesafen, with patches averaging 7.5 and 0.1 first and fifth instars, respectively. In greenhouse experiments, common milkweed survived fomesafen rates up to 0.28 kg ha−1, twice the rate typically used in soybean, and plants showed signs of recovery within two weeks of application.

Herbicide Programs Utilizing Halauxifen-Methyl for Glyphosate-Resistant Horseweed (Conyza canadensis) Control in Soybean

Evolution of glyphosate-resistant (GR) weeds, such as horseweed, presents major challenges in no-till soybean production systems. Effective GR horseweed control with preplant burndown applications is necessary to prevent potential soybean yield losses due to competition and to manage the soil weed seedbank. Halauxifen-methyl is a new synthetic auxin herbicide for broadleaf weed control in preplant burndown applications for soybean and other crops at low use rates (5 g ae ha–1). Experiments were conducted to evaluate the efficacy of herbicide treatments containing halauxifen-methyl for control of GR horseweed in comparison to existing herbicide treatments utilized in no-till GR soybean systems. Glyphosate alone controlled horseweed 33%. Herbicide treatments that included halauxifen-methyl, dicamba, or saflufenacil in combination with glyphosate controlled horseweed 87% to 96%, 89%, and 93%, respectively, 35 d after burndown application (DAB). Horseweed control, horseweed density reduction, and ground cover reduction by halauxifen-methyl plus glyphosate was similar to dicamba plus glyphosate. Horseweed control was greater for halauxifen-methyl plus glyphosate than for 2,4-D plus glyphosate. Cloransulam, cloransulam plus flumioxazin, and cloransulam plus sulfentrazone added to halauxifen-methyl plus glyphosate increased horseweed control and reduced horseweed density. No herbicide injury or soybean yield reduction was observed for treatments containing halauxifen-methyl.

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Groundnut (Arachis hypogea L.) is an important food source as well as cash crop for the people of Northern Ghana. The crop yield is low partly due to biological constraints which include diseases like leaf spot. A survey was conducted among 200 farmers in four districts of the Northern Region of Ghana, from June to August, 2014 using a structured questionnaire. The objectives of this study were to assess farmers’ knowledge, perception and management of leaf spot disease of groundnut. Differences in farmer responses were evaluated using Chi-square test. A significantly higher (P =0.005) number of farmers (87.5 %) were aware of leaf spot disease of groundnut and could identify symptoms of the disease, but could not differentiate symptoms from herbicide injury. Majority (84.5 %) of the farmers reported the incidence of leaf spot disease on their farms to be 50 % and above. Most farmers (74.5 %) also reported the disease severity to be above 50 %. Male farmers (33.5 %) who used defoliation or brown spots as signs of maturity of the groundnut crop were significantly more (P =0.031) than their female counterparts (26 %). Farmers who used non-chemical methods (62 %) of managing leaf spot disease were significantly (P <0.001) higher than those who used recommended methods including the use of chemicals (38 %). It is important to educate farmers to enhance their capabilities for leaf spot disease management through farmers’ field days. Also, since most of them use traditional methods such as crop rotation, appropriate spacing and mixed cropping as means of controlling the disease, and the use of effective plant extracts as an integrated management strategy would be ideal. Key words: Leaf spots, knowledge, perception, management, Northern region.

Solubility, partitioning, oxidation and photodegradation of dichloroacetamide herbicide safeners, benoxacor and furilazole

Approximately 242 million kg of herbicides are applied in the United States (US) annually. While herbicides prevent the growth of weeds, they can damage crops resulting in so called “herbicide injury.” To increase herbicidal tolerance of crops, herbicide safeners are commonly added to formulations. Herbicidal safeners are labeled as inert ingredients in herbicide formulations and typically minimal fate and transport information is available. The objective of this study is to experimentally derive the aqueous solubility, octanol-water partition coefficient, and photo-degradation and permanganate oxidation of two dichloroacetamide safeners, benoxacor and furilazole. These results can be used to understand the environmental chemodynamics of these compounds and their degradation via common drinking water treatment systems containing permanganate. The aqueous solubility of benoxacor and furilazole was 22 and 235 mg L−1 respectively while the estimated solubility from EPI Suite was 102.7 and 255 mg L−1 respectively. The log octanol-water partition coefficient of benoxacor and furilazole was 2.23 and 1.96 respectively. The selected safeners were not photodegradable to any great extent. Both benoxacor and furilazole oxidation were found to be second order with respect to initial KMnO4 concentrations. The results of this study can be used to predict distribution of safeners after application in agricultural fields and aid in the design of treatment systems.

High-Throughput Phenotyping of Seed/Seedling Evaluation Using Digital Image Analysis

Image-based evaluation of phenotypic traits has been applied for plant architecture, seed, canopy growth/vigor, and root characterization. However, such applications using computer vision have not been exploited for the purpose of assessing the coleoptile length and herbicide injury in seeds. In this study, high-throughput phenotyping using digital image analysis was applied to evaluate seed/seedling traits. Images of seeds or seedlings were acquired using a commercial digital camera and analyzed using custom-developed image processing algorithms. Results from two case studies demonstrated that it was possible to use image-based high-throughput phenotyping to assess seeds/seedlings. In the seedling evaluation study, using a color-based detection method, image-based and manual coleoptile length were positively and significantly correlated (p &lt; 0.0001) with reasonable accuracy (r = 0.69–0.91). As well, while using a width-and-color-based detection method, the correlation coefficient was also significant (p &lt; 0.0001, r = 0.89). The improvement of the germination protocol designed for imaging will increase the throughput and accuracy of coleoptile detection using image processing methods. In the herbicide study, using image-based features, differences between injured and uninjured seedlings can be detected. In the presence of the treatment differences, such a technique can be applied for non-biased symptom rating.

Preemergence Herbicide Effects on Hybrid Bermudagrass Root Architecture and Establishment

Preemergence herbicides generally have a negative effect on hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] establishment. However, little is known about the effect they have on root architecture and development. Research was conducted to determine the effects of commonly used preemergence herbicides on ‘Latitude 36’ hybrid bermudagrass root architecture and establishment. The experiment was conducted in a climate-controlled greenhouse maintained at 26 °C day/night temperature at Mississippi State University in Starkville, MS, from Apr. 2016 to June 2016 and repeated from July 2016 to Sept. 2016. Hybrid bermudagrass plugs (31.6 cm2) were planted in 126-cm2 pots (1120 cm3) and preemergence herbicide treatments were applied 1 d after planting at the recommended labeled rate for each herbicide. Preemergence herbicide treatments included atrazine, atrazine + S-metolachlor, dithiopyr, flumioxazin, indaziflam, liquid and granular applied oxadiazon, S-metolachlor, pendimethalin, prodiamine, and simazine. Treatments were arranged in a completely randomized design with four replications. Plugs treated with indaziflam and liquid applied oxadiazon failed to achieve 50% hybrid bermudagrass cover by the end of the experiment. Of the remaining herbicide treatments, all herbicides other than granular applied oxadiazon and atrazine increased the number of days required to reach 50% cover (Days50). In addition, all herbicide treatments reduced root mass when harvested 6 weeks after treatment (WAT) relative to the nontreated. By 10 WAT, all treatments reduced root mass in run 1, but during run 2, only prodiamine, pendimethalin, simazine, atrazine + S-metolachlor, liquid applied oxadiazon, and indaziflam reduced dry root mass compared with the nontreated. At 4 WAT, all treatments other than simazine and granular applied oxadiazon reduced root length when compared with the nontreated. By 10 WAT, only dithiopyr, S-metolachlor alone, and indaziflam reduced root length when compared with the nontreated. No differences were detected in the total amounts of nonstarch nonstructural carbohydrates (TNSC) within the roots in either run of the experiment. Results suggest that indaziflam, dithiopyr, and S-metolachlor are not safe on newly established hybrid bermudagrass and should be avoided during establishment. For all other treatments, hybrid bermudagrass roots were able to recover from initial herbicidal injury by 10 WAT; however, future research should evaluate tensile strength of treated sod.

Impact of fluopyram fungicide and preemergence herbicides on soybean injury, population, sudden death syndrome, and yield

Field experiments were conducted in Indiana and Iowa in 2014 and 2015 to examine the effect of preemergence herbicides and fluopyram seed treatment on soybean (Glycine max (L.) Merr.) injury, plant population, sudden death syndrome (SDS; Fusarium virguliforme O'Donnell & T. Aoki), and yield. Sulfentrazone + cloransulam-methyl + S-metolachlor and flumioxazin + chlorimuron ethyl + S-metolachlor herbicides resulted in higher phytotoxicity at growth stage VC-V1 compared to a non-treated control. Phytotoxicity due to preemergence herbicide was rarely observed at V4. Seed treated with fluopyram resulted in higher phytotoxicity at VC-V1 than seed without fluopyram, regardless of preemergence herbicide treatment. The combination of preemergence herbicide and fluopyram did not increase the severity of soybean injury in any year or location compared to either applied alone. Preemergence herbicide treatment reduced plant population in Indiana in 2014 and Iowa in 2015 compared to the non-treated control, but did not affect yield. Fluopyram seed treatment reduced foliar symptoms of SDS by over 70% and increased yield up to 12% in Indiana, but had no effect on SDS or yield in Iowa. These results indicate that while injury can occur with both preemergence herbicides and fluopyram-treated seed, phytotoxicity is not more severe when both pesticides are used together, and yield is not reduced by their use. Farmers should continue to use preemergence herbicide programs if they treat their seed with fluopyram to manage SDS, and use production practices that minimize the risk of preemergence herbicide injury in soybean.

Effect of Thiamethoxam on Injurious Herbicides in Rice

Increases in the number of herbicide-resistant weeds in rice has led to the need for new herbicides and modes of action to control these troublesome weeds. Previous research has indicated that insecticide seed treatments can safen rice from herbicide drift. In 2014 and 2015, two field experiments were conducted at the Rice Research and Extension Center (RREC) near Stuttgart, Arkansas, and at the University of Arkansas Pine Bluff (UAPB) farm near Lonoke, Arkansas, to determine if insecticide seed treatments could prevent unacceptable levels of herbicide injury from preemergence (PRE)- and postemergence (POST)-applied herbicides that are typically injurious to rice. Both studies were planted with the imidazolinone-resistant, inbred variety CL151. ‘Treated’ plots contained the insecticide seed treatment thiamethoxam while ‘nontreated’ plots contained no insecticide seed treatment. Seven herbicides were evaluated in the PRE experiment: clomazone, pethoxamid, fluridone, S-metolachlor, thiobencarb, clethodim, and quizalofop to determine crop injury, stand counts, groundcover, and rough rice yield with and without an insecticide seed treatment compared to plots with no herbicide treatments. Overall, an insecticide seed treatment provided increased rice stands and less herbicide injury than the ‘nontreated’ seed while increasing yield by 500 kg ha-1. Of the herbicides tested, clomazone-, thiobencarb-, clethodim-, and quizalofop-treated plots had equivalent yields to the no-herbicide plots. The POST experiment evaluated propanil, saflufenacil, carfentrazone, and acifluorfen in various tank-mixtures and application timings. Similar to the PRE experiment, plants from treated seed had less herbicide injury 1 and 5 weeks after treatment (WAT) along with an increased canopy height and groundcover percentage. Plants having treated seed also had increased yields when used with some herbicide programs. Overall, the use of an insecticide seed treatment can give the added benefit of less injury from injurious herbicides as well as increased groundcover.

Evaluation of Herbicides and their Tank‐Mixes for Suppression of Bermudagrass in Zoysiagrass

Zoysiagrass (Zoysia spp.) is a popular turfgrass species for use on lawns, sod farms, and golf courses in the transitional and southern climatic zones of the United States. One common problem in managing zoysiagrass is the contamination and subsequent removal of bermudagrass (Cynodon spp.). Various herbicides and herbicide tank‐mixes may be utilized for bermudagrass control in zoysiagrass. Research was conducted in Fayetteville, AR, and Auburn, AL, to evaluate aminocyclopyrachlor, fluazifop, fenoxaprop, triclopyr, and their combinations for bermudagrass suppression in zoysiagrass. Fluazifop at 0.105 kg active ingredient (a.i.) ha–1 suppressed bermudagrass most, but this application caused unacceptable injury and quality reduction to zoysiagrass. Tank‐mixing fluazifop or fenoxaprop at 0.14 kg ai ha–1 with triclopyr at 0.56 kg acid equivalent (a.e.) ha–1 reduced zoysiagrass injury and improved turf quality over fluazifop or fenoxaprop alone. Fluazifop + triclopyr provided more bermudagrass suppression than fenoxaprop + triclopyr. Aminocyclopyrachlor (0.026 or 0.071 kg a.e. ha–1) did not reduce herbicide injury from fluazifop or fenoxaprop applications to zoysiagrass and did not provide significant bermudagrass suppression. Results suggest that fluazifop + triclopyr and fenoxaprop + triclopyr remain the best treatments for bermudagrass suppression in zoysiagrass because they provide bermudagrass suppression without reducing zoysiagrass quality.

Herbicide injury induces DNA methylome alterations in Arabidopsis.

The emergence of herbicide-resistant weeds is a major threat facing modern agriculture. Over 470 weedy-plant populations have developed resistance to herbicides. Traditional evolutionary mechanisms are not always sufficient to explain the rapidity with which certain weed populations adapt in response to herbicide exposure. Stress-induced epigenetic changes, such as alterations in DNA methylation, are potential additional adaptive mechanisms for herbicide resistance. We performed methylC sequencing of Arabidopsis thaliana leaves that developed after either mock treatment or two different sub-lethal doses of the herbicide glyphosate, the most-used herbicide in the history of agriculture. The herbicide injury resulted in 9,205 differentially methylated regions (DMRs) across the genome. In total, 5,914 of these DMRs were induced in a dose-dependent manner, wherein the methylation levels were positively correlated to the severity of the herbicide injury, suggesting that plants can modulate the magnitude of methylation changes based on the severity of the stress. Of the 3,680 genes associated with glyphosate-induced DMRs, only 7% were also implicated in methylation changes following biotic or salinity stress. These results demonstrate that plants respond to herbicide stress through changes in methylation patterns that are, in general, dose-sensitive and, at least partially, stress-specific.

Effect of Indaziflam Application and Soil Manipulations on Pecan Evapotranspiration and Gas Exchange Parameters

Appropriate soil management practices and correct use of agrochemicals for crop protection are essential to alleviate stresses that affect the quality and yield of pecans [Carya illinoinensis (Wangenh.) K. Koch]. A greenhouse study was conducted to evaluate the effect of soil surface manipulation and indaziflam application on evapotranspiration (ET) and gas exchange parameters of pecan trees, and phytotoxicity effects of indaziflam on pecan trees. Trees were planted in large pots with a homogeneous porous media (HM), including the controls (C), preferential flow channels open at the soil surface (PF), and preferential flow channels with surface soil manually tilled to 5 cm depth [shallow tillage (ST)]. Trees with HM, PF, and ST were treated with 50 g a.i./ha of indaziflam in 2014 and 2015, whereas an application rate of 150 g a.i./ha was used for trees with HM and ST in 2016. All trees were irrigated about every 14 days with 7 L of water in 2014 and 2015, and 5 L in 2016. A water balance analysis determined the ET in different treatments in 2014 and 2015. Gas exchange parameters were measured before and after irrigation in 2015 and 2016. Photosynthetic rates in C, HM, PF, and ST were consistently significantly lower before than after irrigation. PF and ST did not decrease the available water content of the soil because there was no significant difference in the volume of effluent, ET, and gas exchange parameters among the treatments. No herbicide injury symptoms and no influence on gas exchange parameters and ET were observed after using both application rates of indaziflam.

Herbicide Tolerance of Established Buffalograss

Core Ideas Proper calibration and application is important when using herbicides on buffalograss. Established ‘Bowie’ buffalograss was most tolerant to carfentrazone + quinclorac, halosulfuron, indaziflam, quinclorac, quinclorac + MCCP + dicamba, simazine, sulfosulfuron, or thiencarbazone + iodosulfuron + dicamba. Herbicide injury on established buffalograss is relatively short‐lived with the exception of imazapic at the 2× rate.

Agronomic performance of insect-protected and herbicide-tolerant MON 89034 × TC1507 × NK603 × DAS-40278–9 corn is equivalent to that of conventional corn

ABSTRACTAgronomic characteristics of genetically modified (GM) MON 89034 × TC1507 × NK603 × DAS-40278–9 (PowerCore™ Enlist™), MON 89034 × TC1507 × NK603 (PowerCore™), and DAS-40278–9 (Enlist™) corn, a non-GM near-isogenic hybrid, and 2 commercial non-GM hybrids were assessed in a field study to determine if the agronomic performance of the GM corn hybrids is equivalent to that of non-transgenic hybrid corn. The MON 89034 × TC1507 × NK603 × DAS-40278–9 hybrid corn was developed through stacking of 4 individual transgenic events, MON 89034, TC1507, NK603, and DAS-40278–9 by traditional breeding and contains the cry1A.105 and cry2Ab2 (MON 89034), cry1F and pat (TC1507), cp4 epsps (NK603) and aad-1 (DAS-40278–9) transgenes. These transgenes encode the proteins Cry1A.105, Cry2Ab2, and Cry1F, which confer insect resistance, PAT, CP4 EPSPS, and AAD-1, which confer herbicide tolerance. The following agronomic characteristics were assessed in the study: initial and final stand count, seedling vigor, time to silk, time to pollen shed, pollen viability, plant height, ear height, stalk lodging, root lodging, days to maturity, stay green, disease incidence, insect damage, herbicide injury, and yield. The agronomic assessment was conducted in 2 regions of Brazil (Indianopolis-MG; Cravinhos-SP). The agronomic attributes for all GM entries were statistically indistinguishable from the non-GM near-isogenic hybrid. In addition, most of the agronomic assessments fell within the range of the commercial varieties included in the study. Taken together, MON 89034 × TC1507 × NK603 × DAS-40278, MON 89034 × TC1507 × NK603, and DAS-40278–9 were found to be agronomically equivalent to non-GM corn.

Tolerance of Processing Tomato (Solanum lycopersicum) Varieties to Halosulfuron-methyl

Field experiments were conducted at the Ohio Agricultural Research and Development Center in Wooster, OH in 2002 and 2004 to evaluate the tolerance of tomato varieties to halosulfuron-methyl, a selective herbicide used for POST control of broadleaf weeds and nutsedge (Cyperus). POST herbicide treatments included halosulfuron-methyl at 0, 34.7 and 70 gaiha−1. Plots were evaluated at 1, 3, and 6 wk after treatment (WAT), and yield was recorded at the end of the season. Minimal crop injury was observed 1 and 3 WAT in plots treated with both halosulfuron-methyl rates only in 2002. Although the crop recovered from herbicide injury when treated with the lower rate at 6 WAT, ‘Ohio 8245’, ‘M82’, and ‘E6203’ showed injury at this interval when treated with halosulfuron-methyl at 70 g ha−1. No injury was observed with either rates in 2004. No significant yield reduction was observed in any of the varieties in the test plots. These results indicate that differential tolerance to halosulfuron-methyl does not exists among these tomato varieties with the exception of E6203 and M82.

Potential Interaction of Pre-emergence Herbicides and the Efficacy of Insecticide and Fungicide Seed Treatments in Cotton

The increasing presence of glyphosate-tolerant weeds has increased the use of pre-emergence herbicides in cotton, Gossypium hirsutum L., grown in Tennessee during the last 5 to 8 years. These herbicides could have negative effects on seedling growth and potentially affect thrips (Thysanoptera: Thripidae) management or seedling disease with at-planting insecticides or fungicides. Experiments were conducted in 2013 and 2014 to evaluate the potential interactions of pre-emergence herbicides on the efficacy of insecticide or fungicide seed treatments in cotton. Nontreated plots and plots treated with a thiamethoxam seed treatment generally exhibited higher number of thrips, more thrips injury, less vigor, delayed maturity, and lower yields compared to plots treated with an imidacloprid seed treatment or an in-furrow application of aldicarb. Similarly, fungicide seed treatments generally reduced the incidence of seedling disease (primarily Rhizoctonia), while improving seedling health and stand density. Negative effects of some pre-emergence herbicides on plant health also were observed. For example, combination treatments of fluometuron plus S-metolachlor or fluometuron plus fomesafen reduced plant vigor and seedling biomass and there was a tendency for higher thrips populations where pre-emergence herbicides were used. There were no substantial interactions between injury caused by pre-emergence herbicides and that caused by thrips or seedling disease suggesting that thrips, seedling disease, and herbicide injury acted independently and additively. Following herbicide label rates should reduce the risk of compounding the effects of thrips or seedling disease with herbicide injury.

Applications of Unmanned Aerial Vehicles in Weed Science

For most producers, unmanned aerial vehicles (UAV) are a novelty that has been little employed in their agricultural operations. An UAV will not fix every problem on the farm, but there are some practical applications for which UAVs have demonstrated value. Three examples of how UAVs have been used in weed science applications are presented here; the methods are transferable to other agricultural commodities with similar characteristics. The first of these is quantification of the extent and severity of non-target herbicide injury. The second application is calculation of spray thresholds based on weed populations. The third application is development of site-specific herbicide treatment.

Early‐Season Lactofen Application Fails to Increase Soybean Yield under Weed‐Free Conditions

In an effort to increase soybean [Glycine max (L.) Merr.] yield, growers may consider non‐traditional use of crop inputs. One non‐traditional input use is the application of lactofen {2‐ethoxy‐1‐methyl‐2‐oxoethyl 5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoate} herbicide to early‐vegetative soybean to promote increased branch development and ultimately increase seed yield. The purpose of this study was to evaluate the effect of early‐season lactofen application and simulated herbicide injury on stands, plant height, light interception, and seed yield. The experiments were conducted at two locations in Kentucky during the 2013 and 2014 growing seasons. Treatments included lactofen herbicide applied at 240 g a.i. ha−1 and fomesafen {5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐N‐methylsulfonyl‐2‐nitrobenzamide} herbicide applied at 600 g a.i. ha−1. A meristem removal treatment was included, where the apical meristem of each soybean was physically removed, and a leaf removal treatment was also performed. All treatments were applied to soybean at V1, V2, V3, and V4 growth stages. The herbicide application timing had no effect on any of the above mentioned agronomic measurements. The apical meristem removal reduced plant stands and plant height in 2 site‐years while lactofen and leaf removal decreased early‐light interception in all site‐years. Meristem removal and leaf removal reduced seed yield in 1 site‐year, while lactofen, leaf removal, and meristem removal reduced seed yield in another site‐year. None of the treatments increased seed yield compared with the untreated control. Despite a limited number of trials, this study suggests that application of lactofen to soybean for non‐weed control purposes is not a viable strategy to increase soybean yield.Core Ideas Leaf removal and lactofen application decrease early‐season light interception in soybean. Destroying the soybean apical meristem either decreases or does not affect soybean yield. Lactofen application to early vegetative soybean does not increase yield under weed free conditions.

Herbicide tolerance of Euphorbia lagascae Spreng., (Euphorbiaceae)

Euphorbia lagascae Spreng., (Euphorbiaceae), (abbreviated EPHLA), has good potential to become an important crop and source of epoxy fatty acids in semi-arid regions. Crop yield is enhanced with good weed control, and this study examined EPHLA’s tolerance to several pre-plant incorporated (PPI), pre-emergence (PRE), and post-emergence (POST) herbicides, as well as seed and oil production factors. Preliminary tests were done in a greenhouse, and more involved studies were done in the field. The most promising PPI and PRE herbicides included benefin, ethalfluralin, trifluralin, and pendimethalin. Chloridazon and DCPA also gave reasonably good results, but rate and timing may be important when using these herbicides. Diuron and EPTC injured EPHLA and were poor herbicide candidates for EPHLA. The most promising POST herbicides included clopyralid, alachlor, acifluorfen, and chloridazon, to which EPHLA exhibited very good tolerance and very good to excellent yields. Oxyfluorfen and bromoxynil caused significant vegetative injury, but EPHLA produced good to excellent yields, suggesting that the herbicide injury was temporary. Bentazon and DCPA caused a moderately low degree of injury to EPHLA, which responded with a somewhat decreased seed yield, indicating that the effect of rate and timing may be important for these herbicides. Several POST herbicides, including metsulfuron, imazapyr, imazethapyr, imazamox, ethofumesate, and dicamba, caused a low degree of visible injury to the EPHLA, but EPHLA seed yield was very low, suggesting that these herbicides injured EPHLA’s reproductive processes. Picloram and 2,4-D caused severe damage or death to EPHLA. Because several PPI, PRE, and POST herbicides caused severe damage to EPHLA, they could be useful if EPHLA escaped cultivation to become a weed problem.

3-Dichloroacetyl oxazolidine protect maize from imazethapyr herbicide injury

ABSTRACT 3-Dichloroacetyl oxazolidine protect maize from imazethapyr herbicide injury Li-Xia Zhao 1 , Hao Wu 1 , Ying Fu 1 , Yue-Li Zou 1 , and Fei Ye 1* RESEARCH 1 Northeast Agricultural University, College of Science, Harbin, Heilongjiang Province, 150030, China. * Corresponding author (yefei@neau.edu.cn).Received: 9 September 2015.Accepted: 27 January 2016.doi:10.4067/S0718-58392016000200004 RESEARCH INTRODUCTION Imazethapyr .[( RS )-5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid], an imidazolinone herbicide, was discovered in the 1980s. Imazethapyr controls weeds by inhibiting the activity of acetolactate synthase (ALS) which catalyzes the first step in the biosynthesis of valine, leucine and isoleucine (Maja and Branko, 2011). Imazethapyr has been used worldwide in weed control. As a consequence, phytotoxic effects to certain rotational crops were observed because of imazethapyr residue in cultivation soil and weed resistance to imazethapyr has developed into a more serious problem (Zhou et al., 2009; Pinto et al., 2009; Heap, 2014). Herbicide safeners are a group of synthetic compounds that could protect selected plants against herbicide injury without decreasing herbicidal activity to target weeds (Kraehmer et al., 2014). In 1947, Hoffman realized that safener was a useful tool to protect crop from herbicide injury. Nearly 20 safeners has subsequently been developed and commercialized by famous agrochemical companies (Jablonkai, 2013). While the exact mechanism of safener is still not completely understood, it seems that safeners could increase crop tolerance by inducing the activity of detoxifying enzyme glutathione

Herbicide Control Strategies for Ventenata dubia in the Intermountain Pacific Northwest

Ventenata dubia is an exotic annual grass that has become increasingly invasive in various perennial grass systems throughout the Intermountain Pacific Northwest. Currently, little information is available to landowners about herbicide control options. In our first field study, we evaluated V. dubia control efficacy and perennial grass tolerance of herbicides applied pre-emergence (PRE) at two locations and as an early postemergence (EPOST) application at four different conservation reserve grasslands, with each grassland dominated by different perennial grass species. Treatments included flufenacet plus metribuzin (303 + 76 g ai ha−1 [0.27 + 0.07 lb ai ac−1]), propoxycarbazone-sodium (49 g ai ha−1 [0.04 lb ai ac−1]), rimsulfuron (53 g ai ha−1 [0.05 lb ai ac−1]), sulfosulfuron (53 g ai ha−1 [0.05 lb ai ac−1]), and imazapic (105 g ai ha−1 [0.09 lb ai ac−1]). Rimsulfuron and flufenacet plus metribuzin applied PRE provided &gt; 90% control 10 mo after treatment (MAT). Rimsulfuron and sulfosulfuron applied EPOST provided &gt; 90% control 9 MAT. Herbicide injury to bluebunch and intermediate wheatgrass was negligible across treatments. Imazapic and sulfosulfuron applied EPOST resulted in significant injury to smooth brome and timothy. In our second study, we addressed the following question: Will fall herbicide plus fertilizer treatments improve V. dubia control compared with herbicide treatments alone? We imposed fall herbicide treatments in main plots and fertilizer treatments (fall N, fall P, fall K, fall PK, spring N, NPK) in split plots at three study locations. Herbicide treatments resulted in high levels of V. dubia control. Differences in V. dubia abundance among fertilizer treatments were negligible 9 MAT. Within herbicide control plots, spring N and NPK treatments resulted in significant increases in perennial grass cover and decreases in V. dubia cover (9 MAT). This result indicates that spring N applications timed to the onset of perennial grass growth could be utilized as a component of an integrated management strategy for V. dubia in invaded perennial grass systems.