Herbicide Injury Research Articles

Understanding Mechanisms of Herbicide Selectivity in Agro-Ecosystems: A Review

Weeds cause yield losses in desired crops through competition for sunlight, water, space, and nutrients. It is important to manage weeds in crop fields and aqua bodies using various management strategies. One of the most effective and efficient ways of managing weeds is through the use of herbicides. However, there is a need to understand the effects of these herbicides on the desired plants and/or the environment. Herbicide selectivity allows the application of herbicides in a field with both the desired crop and weeds. Herbicide selectivity is therefore described as, an application treatment at a given dosage that is toxic to some plant species but does not damage another species. However, many herbicides can be toxic at high dose rates even when applied to tolerant crops. There are several mechanisms of herbicide selectivity which are grouped into physiological and physical. Physical herbicide selectivity occurs when physical factors such as time, the position of application, plant morphological structure, and environment aid in selectivity. Physiological selectivity occurs when the plant species affect herbicide retention, penetration, movement, and detoxification. Herbicide selectivity is known to be a major cause of difficulties in controlling weeds. As a result, there is a need to understand how the environment, herbicides, and plants contribute to selectivity. This paper, therefore, provides insights into herbicide selectivity and how plants escape herbicide injury which enables species diversity.

Condições ambientais que afetam a seletividade de herbicidas em arroz irrigado no Sul do Brasil

ABSTRACT: Rice yield in Southern Brazil has increased linearly over the years. Early season sowing is the primary contributor to rice yield increase in Southern Brazil. However, that practice might expose rice seedlings to the risk of low-temperature stress, which can enhance herbicide injury and reduce rice yield. This research evaluated the effect of sowing dates on herbicide selectivity and agronomical rice traits. We conducted field experiments during the 2010/11 and 2011/12 growing seasons in Capão do Leão, RS, Brazil. The experimental design was a complete randomized block with a factorial arrangement. Factor A was early-sowed (in September) and late-sowed (in November); factor B was herbicide treatment (bispyribac-sodium, cyhalofop-butyl penoxsulam, metsulfuron-methyl, and nontreated check). Rice response to herbicide treatments differed between years. In 2010/11, bispyribac-sodium, penoxsulam, and metsulfuron-methyl injured rice only on early-sowed. In both years, early sowing rice promoted higher yield potential despite herbicide injury. The injury caused by the herbicides bispyribac-sodium, penoxsulam and metsulfurom-methyl was transient did not lead to yield losses. Cold temperature close the application increases the injury of ALS herbicides.

Assessment of genetic variation for herbicide tolerance in sesame (Sesamum indicum L.) germplasm

To assess genetic variation for herbicide tolerance in sesame, a set of 55 genotypes were sprayed with imazethapyr@75g ai/ha on the 18th day after sowing at seedling stage. A control plot without herbicide spray was maintained. The injury caused due to Imazethapyr spray was recorded visually on 1-5 scale and the survival rate was calculated on 7th, 10th, 13thand 15th day after treatment. The herbicide injury rating ranged from 2-4.8 on 7thday after herbicide spray (DAHS) and 3.7 -5.0 on the 15th DAHS. The survival rate progressively decreased from 7th DAHS to 15th DAHS inmost genotypes. The genotype, NIC-8261 was the most sensitive genotype expressing the symptoms of herbicide injury at a very early stage. On the 15th DAHS, only 10 genotypes viz., CO-1, OTS-2, SI-328, SI-3171, NIC-16106, G-53, SI-1769, TC-25, RT-146 and NIC-8317 had a survival rate ranging from27% to 39%. The subset of 10 genotypes was further evaluated for growth and yield attributes to assess the effect of imazethapyr spray on them. Imazethapyr spray resulted in delayed flowering and adversely caused a reduction in plant height, number of capsules per plant, seeds per capsule, thousand seed weight and seed yield per plant in the sesame genotypes. The findings of the study indicated that Imazethapyr@75gai/ha applied as a post-emergence herbicide at seedling stage was toxic to sesame and caused adverse effects on sesame growth and yield, by reducing the plant height, capsule production, thousand seed weight and also caused a delay in flowering. The response of sesame genotypes to Imazethapyr application was variable suggesting that genetic variability exists for herbicide tolerance in the germplasm, which need to be studied intensively.

A Mini Review on Natural Safeners: Chemistry, Uses, Modes of Action, and Limitations.

Herbicide injury is a common problem during the application of herbicides in practice. However, applying herbicide safeners can avoid herbicide damage. Safeners selectively protect crops against herbicide injury without affecting the biological activity of herbicides against the target weeds. However, after long-term application, commercial safeners were found to pose risks to the agricultural ecological environment. Natural safeners are endogenous compounds from animals, plants, and microbes, with unique structures and are relatively environment-friendly, and thus can address the potential risks of commercial safeners. This paper summarizes the current progress of the discovery methods, structures, uses, and modes of action of natural safeners. This study also concludes the limitations of natural safeners and prospects the future research directions, offering guidance for the practical application of natural safeners to prevent herbicide injury. This study will also guide the research and development of corresponding products.

Field performance of a red clover germplasm selected for increased tolerance to 2,4-D

AbstractThis study compared the field performance of red clover germplasm UK2014, selected for 2,4-D tolerance, to Kenland, a standard variety grown in the transition zone of the United States. UK2014 and Kenland were seeded in the spring of 2017 and 2018. Single applications of 0, 1.12, or 2.24 kg ae ha−1 2,4-D-amine were made in June, August, or October. One week after the treatments, yields were determined. Visible herbicide injury ratings were made prior to harvest and regrowth was visibly assessed 1 wk after harvest. Red clover stands were visibly assessed the following spring. Kenland, across all application timings, was injured by 2,4-D more than UK2014, with mean injury ratings of 39% and 63% compared with 26% and 37% at 1.12 and 2.24 kg 2,4-D ae ha−1, respectively. At equivalent rates, Kenland regrowth was less than UK2014 at all application timings. UK2014 regrowth after 2,4-D treatment ranged from 65% to 91%, whereas Kenland regrowth ranged from 12% to 72%. Applications of 2,4-D in October were the most damaging to stands of both UK2014 and Kenland the following spring, but Kenland stands were reduced much more than those of UK2014. Kenland and UK2014 had similar season total yields when not treated with 2,4-D (means of 7,550 and 7,880 dry matter kg ha−1, respectively in 2017 and 5,280 dry matter kg ha−1 for both in 2018). Kenland season total yield in 2017 was reduced by both 2,4-D rates applied in June or August and at all timings in 2018. UK2014 season total yield in 2017 was reduced only when 2.24 kg 2,4-D ae ha−1 was applied in August. In 2018, 2.24 kg ae ha−1 2,4-D resulted in reduced UK2014 season total yield across application timings. UK2014 has greater 2,4-D tolerance than Kenland, but additional selection might be beneficial.

Current Advances in the Action Mechanisms of Safeners

Herbicide safeners are a series of agrochemicals that can selectively protect crop plants from herbicide injury without affecting herbicidal efficacy. Understanding mechanisms by which safeners act is significant for discovery of novel types. Safeners primarily alleviate herbicide phytotoxicity to crop plants via several actions: (i) enhancing metabolism of herbicides in crops; (ii) affecting absorption and transportation of herbicides in crops; (iii) competitively binding to herbicide target sites; and (iv) affecting activity of target enzymes. This review describes recent advances in the action mechanisms of safeners, analyzes existing problems, anticipates the future direction of studies of modes of action of safeners, and prospects potential strategies to design safeners related to their reported mechanisms. The aim of this paper is to provide insight into mechanisms of safeners and give tips for development of new safeners.

Effects of Different Environment-Friendly Gibberellic Acid Microcapsules on Herbicide Injury of Wheat.

Environmentally friendly microcapsules are becoming more and more widely used due to the increasing demand for environmental safety in pesticides. To compare the impact of differences in wheat herbicide phytotoxicity of different gibberellic acid microcapsule suspensions, two microcapsule suspensions were separately formulated using the phase transfer method and the in situ polymerization method, and the key performance indicators are the size of microcapsules and the degree of encapsulation. Meanwhile, through field trials, the pharmacological and detoxification effects of different types of microcapsule suspensions on the herbicide methyldisulfuron in wheat fields were compared. The microcapsule suspension was prepared by the phase transfer method and the particle sizes D10, D50, and D90 are 0.990, 2.136, and 5.201 μm, respectively; the microcapsule suspension was prepared by the in situ polymerization, the particle sizes D10, D50, and D90 are 4.365, 8.547, and 16.782 μm, respectively. The encapsulation rate of the microcapsules prepared by the phase transfer method and the in situ polymerization method was 86.9% and 91.2%, being higher than 80%, the national standard for capsules. Meanwhile, the release rate conforms to first-order release kinetics in 0–4 days and zero-order release kinetics in 5–28 days. The plot trials' result showed that the detoxification effect of the microcapsules prepared by the in situ polymerization method was significantly better than the detoxification effect of the microcapsules prepared by the phase transfer method and the control agent. The growth index of wheat was higher than that of the untreated check after using the agent.

Reflectance Signatures Developed from Multi-Spectral Imaging of Peanut (Arachis hypogaea L.) Expressing Visible Herbicide Injury

Multi-spectral imaging can be used to define a number of abiotic and biotic stresses associated with crop production and management. Research was conducted during 2004 and 2005 to develop spectral signatures of peanut leaves expressing visual symptoms of herbicide injury. Single leaf measurements using an artificial light source were used to develop spectra ranging from 350 to 2500 nm grouped into specific categories. Reflectance was determined for plants treated with acifluorfen, bentazon, clethodim, imazapic, paraquat, or 2,4-DB at 3 and 24 h and 3 and 6 d after application. Reflectance following herbicide applications was significant at bands 470-500 nm, 500-590 nm, 800 nm, and UMIR, at 3 and 24h after treatment and for bands 470-500 nm, 500-590 nm, 680-700 nm, 800 nm, and UMIR at 3 and 6d after treatment. Differences in reflectance were observed when comparing herbicides with different sites of action, especially when measurements were taken 3 and 6 d after treatment. These results indicate that there is potential for multi-spectral imaging to be used to discriminate among herbicides with different sites of action.

Spatially Resolved Investigation of Herbicide-Safener Interaction in Maize (Zea mays L.) by MALDI-Imaging Mass Spectrometry.

Monitoring agrochemical distribution within plant tissues delivers significant insights into the adsorption, distribution, metabolism, and elimination of agrochemicals. Detection and imaging of the safener cyprosulfamide (CSA) and the herbicide thiencarbazone-methyl (TCM) after micro-droplet application on the surface of maize leaves (Zea mays L.) have been achieved using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI). The agrochemicals were deposited onto the adaxial surface of maize leaves on growing plants, and their uptake, distribution, and metabolism were investigated at four timepoints (3 h, 24 h, 4 days, and 7 days) to assess the influence of CSA treatment on TCM metabolism. MALDI MSI visualized significant changes for the metabolism of TCM after 24 h. Although TCM metabolism was detected neither in the control without the safener nor in the approach with CSA on the second leaf, the co-application on the same leaf showed significant metabolism of the herbicide by detecting the metabolite N-demethylated TCM. These findings suggest that safener protection against herbicide injury is a rapid process in which CSA and TCM need to be present in the same tissues. This study showcases the use of MALDI MSI to visualize and analyze indirect interactions of two substances in planta.

Research Progress in the Design and Synthesis of Herbicide Safeners: A Review

Detoxification plays an important role in herbicide action. Herbicide safeners selectively protect crops from herbicide injury without reducing the herbicidal efficiency against the target weeds. With the large-scale use of herbicides, herbicide safeners have been widely used in sorghum, wheat, rice, corn, and other crops. In recent years, an increasing number of unexpected new herbicide safeners have been designed. The varieties, structural characteristics, uses, and synthetic routes of commercial herbicide safeners are reviewed in this paper. The design ideas and structural characteristics of novel herbicide safeners are summarized, which provide a basis for the design of bioactive molecules as new herbicide safeners in the future.

The Viral Threat in Cotton: How New and Emerging Technologies Accelerate Virus Identification and Virus Resistance Breeding.

Cotton (Gossypium spp. L., Malvaceae) is the world’s largest source of natural fibers. Virus outbreaks are fast and economically devasting regarding cotton. Identifying new viruses is challenging as virus symptoms usually mimic nutrient deficiency, insect damage, and auxin herbicide injury. Traditional viral identification methods are costly and time-consuming. Developing new resistant cotton lines to face viral threats has been slow until the recent use of molecular virology, genomics, new breeding techniques (NBT), remote sensing, and artificial intelligence (AI). This perspective article demonstrates rapid, sensitive, and cheap technologies to identify viral diseases and propose their use for virus resistance breeding.

Direct comparisons of four irrigation systems on a commercial rice farm: Irrigation water use efficiencies and water dynamics

This two-year field study compared the industry-standard rice (Oryza sativa L.) irrigation practice, a continuous-flood delivered using cascade distribution (CASC), to two related levee-based systems (multiple-inlet rice flood distribution (MIRI) and MIRI plus alternate wetting-drying flood management (AWD)) and one furrow-irrigated with end-blocking (ROW) system. Seasonal applied irrigation, soil volumetric water holding content, water depth, grain yield and irrigation water use efficiency (IWUE) were determined for sixteen 16-ha commercial rice fields sown using the same hybrid each year. Also, runoff from one field for each system was measured each year. Average seasonal irrigation applications were 824 ± 197 mm for CASC, 641 ± 165 mm for MIRI, 696 ± 181 mm for AWD and 631 ± 125 mm for ROW. Although a minimum of two AWD dry-down cycles were performed each year and runoff was the least from MIRI (5% runoff) and AWD (3% runoff), ROW (13% runoff) was the only system to receive less irrigation (p = 0.0314) than CASC (14% runoff). In terms of grain yield, only the ROW fields, with an average yield of 8890 ± 417 kg ha−1, differed (p = 0.0107) from CASC (9991 ± 751 kg ha−1). This reduction in ROW yield was due primarily to herbicide injury in 2018 and resulted in average irrigation water use efficiency (IWUE) values that were not different between irrigation treatments (p > 0.05). Taken together, ROW with end-blocking (a) proved to be a more consistent method of water conservation than MIRI and AWD under field conditions complicated by variable soil textures, and (b) lends itself to automation as the ROW fields were irrigated regularly, on a three-to-four-day schedule, rather than depending on human judgement to decide when to irrigate as was required for CASC, MIRI and AWD.

Effect of Soil Moisture Regimes on the Glyphosate Sensitivity and Morpho-Physiological Traits of Windmill Grass (Chloris truncata R.Br.), Common Sowthistle (Sonchus oleraceus L.), and Flaxleaf Fleabane [Conyza bonariensis (L.) Cronq.

The glasshouse study was conducted with the objectives of (i) investigating the effect of soil moisture variations on the control efficiency of glyphosate on windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronq.], (ii) evaluating the tolerance of tested weed species under soil moisture variations, and (iii) determining the morphological and physiological characteristics of these species to partially explain herbicide tolerance under periods of reduced soil moisture availability (RSM). The species’ tolerance to glyphosate increased significantly under reduced soil moisture availability (p < 0.001). The lethal dose to cause herbicide injury or biomass reduction by 50% (LD50) and 80% (LD80) in relation to untreated control for water-stressed plants [i.e., moderate soil moisture availability (MSM) and RSM] was significantly higher than that of plants grown under high soil moisture availability (HSM). The tolerance factor (TF) for C. truncata, S. oleraceus, and C. bonariensis, in terms of biomass reduction under RSM, was 2.6, 2.4, and 2.6, respectively, as compared to HSM. The results showed that the glyphosate sensitivity, especially at the sub-lethal rates, of the three weed species under study decreased as soil moisture availability reduced (p < 0.01). Overall glyphosate efficacy, in relation to the recommended rate, was unaffected, except for C. truncata; the weed survived the highest tested glyphosate rate [750 g active ingredient (a.i.) ha−1] under RSM. There was significant interaction between weed species and soil moisture regimes for weed morpho-physiological traits (p < 0.001), with reduced soil moisture having a more influential impact on the growth of C. bonariensis and S. oleraceus compared to C. truncata. Changes in the leaf characteristics, such as increased leaf thickness, higher leaf chlorophyll content, reduced leaf area, and limited stomatal activity for all the tested weed species under MSM and RSM in relation to HSM, partially explain the tolerance of species to glyphosate at sublethal rates.

Herbicide options to manage novel turf-type bahiagrass (Paspalum notatum)

AbstractHerbicide management information is lacking for recently developed turf-type bahiagrass germplasm. The objective of this study was to evaluate the herbicide tolerance of nine experimental bahiagrass genotypes compared to the industry standard ‘Argentine’. The experimental entries included Argentine and ‘Wilmington’ mutants, and wild-type breeding lines. Plants were grown under greenhouse conditions, and 12 herbicides were applied at 1× and 2× labeled rates. Bentazon, bromoxynil, carfentrazone + 2,4-D + MCPP + dicamba, and carfentrazone were classified as safe. Fluroxypyr, halosulfuron, and triclopyr + clopyralid reduced growth &gt;50% when applied at twice the label rate. Fenoxaprop, sulfentrazone + imazethapyr, and thiencarbazone + iodosulfuron + dicamba reduced growth and caused turfgrass injury above an acceptable threshold (≥20%). In general, the Argentine mutants showed greater herbicide injury compared to the Wilmington mutants. However, metsulfuron exceeded the acceptable injury threshold and stopped growth in all the genotypes, Argentine and genotype WT6 were the least injured by this herbicide. The experimental genotype WT6 consistently showed the greatest herbicide tolerance. Except for one genotype (WT4), the experimental genotypes responded similarly or better than Argentine to the tested herbicides, except for metsulfuron.

Antitranspirants Partially Mitigate Auxin Herbicide Injury on Tomato Plants

The use of dicamba and 2,4-D products on herbicide-tolerant crops has resulted in numerous cases of off-target movement and injury to sensitive plants, including tomato (Solanum lycopersicon L.). Two greenhouse studies were conducted to determine whether ‘Big Beef’ (‘BB’) or ‘Florida 91’ (‘FL’) tomato plants pretreated with an antitranspirant, including Moisture-Loc (ML) at 100 mL·L−1, TransFilm (TF) at 50 g·L−1, or Wilt-Pruf (WP) at 100 mL·L−1, mitigated injury from synthetic auxin herbicides. Dicamba or 2,4-D was applied at a rate corresponding to 1/200 of the manufacturer’s labeled rate of 0.56 kg ae/ha or 1.06 kg ae/ha, respectively. At 2 weeks after treatment (WAT), plants treated with ML or WP before either herbicide exhibited injury symptoms, but they were always less severe than those treated with the herbicide alone for both cultivars. However, shoot length measurements indicated that none of the antitranspirants consistently provided protection against herbicide injury at 2 WAT. By 12 WAT, ML or WP used before either herbicide increased the number of live reproductive organs compared with dicamba or 2,4-D alone for both cultivars. Floral abortion on tomato plants was also reduced when ML or WP was applied before an herbicide treatment by 12 WAT. Although WP and ML did not provide complete protection against synthetic auxin herbicide injury, the concept of using film-forming barriers may be useful in mitigating some of the short-term effects of drift on plants.

Evaluation of Chemical Control Methods of Fountain Grass

Fountain grass (Pennisetum alopecuroides) is a common ornamental grass because of its glossy foliage and showy inflorescence. However, there have been reports of populations growing outside of cultivation and demonstrating invasive tendencies. There is limited research of the chemical control of fountain grass in natural areas. The objective of this experiment was to evaluate the impact of glyphosate, sethoxydim, and fluazifop on fountain grass. Treatments consisted of 2250 and 4500 g⋅ha–1 glyphosate, 262.5 and 525 g⋅ha–1 sethoxydim, and 200 and 400 g⋅ha–1 fluazifop; a nontreated control group was also included. The percent herbicide injury was determined visually 1, 3, 4, 6, and 10 weeks after treatment (WAT). Both rates of glyphosate resulted in 100% of the foliage injured by 3 WAT. The application of flauzifop and sethoxydim led to intermediate results ranging from 15% to 23% injury by 6 WAT, with no significant difference between active ingredients or rates. Nontreated control plants exhibited little to no injury throughout the study. Flauzifop, sethoxydim, and glyphosate all caused visible injury to fountain grass. For complete, fast-acting control, glyphosate is recommended. Herbicide control coupled with restorative plantings of native plants can help reduce invasive plant pressure and improve biodiversity of natural areas.

Herbicide alternative for Conyza sumatrensis control in pre-planting in no-till soybeans

Background In the last two decades, herbicide-resistant biotypes of Conyza bonariensis, Conyza canadensis, and Conyza sumatrensis were identified. Objective: To evaluate herbicide alternatives for the control of C. sumatrensis to replace simplified management at soybean pre-sowing in the no-till system and assess the potential herbicide injury to soybeans. Methods Four experiments were conducted in Palotina, PR, to evaluate alternative managements to the herbicides commonly used in C. sumatrensis , such as synthetic auxins, pre-emergent, and burndown herbicides. All consisted [...]

Fragmenlt Recombination Design, Synthesis, and Safener Activity of Novel Ester-Substituted Pyrazole Derivatives.

Fenoxaprop-p-ethyl (FE), a type of acetyl-CoA carboxylase (ACCase) inhibitor, has been extensively applied to a variety of crop plants. It can cause damage to wheat (Triticum aestivum) even resulting in the death of the crop. On the prerequisite of not reducing herbicidal efficiency on target weed species, herbicide safeners selectively protect crops from herbicide injury. Based on fragment splicing, a series of novel substituted pyrazole derivatives was designed to ultimately address the phytotoxicity to wheat caused by FE. The title compounds were synthesized in a one-pot way and characterized via infrared spectroscopy, 1H nuclear magnetic resonance, 13C nuclear magnetic resonance, and high-resolution mass spectrometry. The bioactivity assay proved that the FE phytotoxicity to wheat could be reduced by most of the title compounds. The molecular docking model indicated that compound IV-21 prevented fenoxaprop acid (FA) from reaching or acting with ACCase. The absorption, distribution, metabolism, excretion, and toxicity predictions demonstrated that compound IV-21 exhibited superior pharmacokinetic properties to the commercialized safener mefenpyr-diethyl. The current work revealed that a series of newly substituted pyrazole derivatives presented strong herbicide safener activity in wheat. This may serve as a potential candidate structure to contribute to the further protection of wheat from herbicide injury.

Potato injury risk and weed control from reduced rates of PPO-inhibiting herbicides

AbstractThe ability to use the protoporphyrinogen oxidase (PPO)-inhibiting herbicides fomesafen, flumioxazin, and sulfentrazone in potato is limited regionally or by soil texture, largely because of crop injury noted in research in the 1990s. With that in mind, we evaluated whether reducing the herbicide rates could maintain weed control while providing more consistent crop safety. Studies were conducted on a silt loam and a coarse-textured loamy sand soil. Soil texture played a greater than anticipated role in PPO-inhibitor herbicide injury risk as it relates to high-precipitation events. For example, in 2020 at the silt loam location, there were five precipitation events across the season that exceeded 2.5 cm, including one 6 d after treatment (DAT), and a seasonal total precipitation that was over 10 cm greater than the previous year. Despite excessive moisture and initial potato injury as high as 27% where flumioxazin was applied at the high rate with S-metolachlor, by 29 DAT injury was less than 10% in all treatments, and marketable tuber yield was similar among treatments. In contrast, in 2020 at the loamy sand location, there were four precipitation events across the season that exceeded 2.5 cm, and potato injury was as much as 60%. In 2020 the high amount of injury from flumioxazin was hypothesized to be caused by precipitation before herbicide application and not after, suggesting a need for more research in this area. This work documents the fine line between yield reduction presumably caused by reduced weed control and yield reduction assumed to be related to herbicide injury. This delineation between adequate weed control and consistent crop safety may differ by soil texture and environmental conditions, supporting the notion that custom-tailored weed management may become more necessary as high-precipitation events become more common in upper midwestern U.S. agricultural systems.

Field Response of Green Ash (Fraxinus pennsylvanica) and Honey Locust (Gleditsia triacanthos) to Aminocyclopyrachlor1

AbstractField trials were conducted to assess the impact of aminocyclopyrachlor on green ash (Fraxinus pennsylvanica Marshall) and honey locust (Gleditsia triacanthos L.) trees in an urban environment. Aminocyclopyrachlor is a relatively new, selective, plant-growth-regulator herbicide in the pyrimidine carboxylic acid family. Treatments were applied to Kentucky bluegrass (Poa pratensis L.) sod growing with and without trees present. Evaluations included determination of a safe spraying distance from target trees and the effect of application timing on tree response. This multi-year study showed that green ash was highly tolerant to aminocyclopyrachlor while honey locust developed severe injury in trees closest to applications. Honey locust trees up to 7 m (23 ft) from the tree trunk to the edge of the application displayed moderate to severe injury symptoms and fall treatment in October and November had the lowest tree injury compared to all other application timings. Honey locust trees exhibiting moderate to severe cosmetic injury would not be acceptable to landowners; recovery over time was minimal. Trees located 13 m (43 ft) away displayed no injury for any treatment timing. Soil analysis demonstrated that aminocyclopyrachlor dissipation was the same underneath green ash and honey locust trees, and that dissipation was faster in the presence of growing trees. Taken together, these results provide a basic groundwork necessary for improving aminocyclopyrachlor labels, and a better understanding of this herbicide's effect on certain woody species.Index words: Herbicide injury, aminocyclopyrachlor, herbicide fate, tree safety.Species used in this study: Green ash, Fraxinus pennsylvanica Marshall, honey locust, Gleditsia triacanthos L.Chemicals used in this study: Aminocyclopyrachlor.