Properties of acetolactate synthase from sulfonylurea-resistant Scirpus juncoides Roxb. var. ohwianus T. Koyama

Properties of acetolactate synthase (EC 4.1.3.18; ALS) from sulfonylurea-resistant (SUR) Scirpus juncoides Roxb. var. ohwianus T. Koyama were studied biochemically and physiologically in comparison with those from sulfonylurea-susceptible weed (SUS). GR₅₀ values for growth inhibition and I₅₀ values for ALS inhibition by imazosulfuron were determined for both SUR and SUS. Imazosulfuron controlled the SUS above 80% at the dosage more than 10 g a.i./ha but did not control the SUR at the even great dosage of 1000 g a.i./ha. The rates required for 50% growth inhibition of the SUR relative to the SUS (R/S ratio) were 271-fold. The I₅₀ value for inhibition of ALS from the SUS was 15 nM, compared to I₅₀ of >3000 nM for inhibition of ALS from the SUR. These results suggest that a resistance may due to an altered ALS that is insensitive to imazosulfuron. The K_m (pyruvate) value of ALS from the SUR was similar to the K_m for ALS from the SUS, suggesting that a mutation resulting in resistance does not change the affinity of the enzyme for pyruvate. The specific activity of the SUR ALS was similar to that of the SUS ALS, which indicates that resistance is not an over-expression of the enzyme. ALS activity from both biotypes was inhibited by isoleucine, valine, and leucine in this order. However, the SUR ALS was less sensitive to inhibition by valine than the SUS ALS.     

有机硅喷雾助剂对草甘膦在空心莲子草上的沉积和生物活性的影响

研究了有机硅喷雾助剂(OSA)对草甘膦在空心莲子草Alternanthera philoxeroides上的沉 积与生物活性的影响。当采用较大喷雾雾滴,施药液量高于632.5 L/hm2时,添加OSA(0.35 g/L) 后,草甘膦药液在空心莲子草上的沉积量显著下降。最大稳定持留量(MRG)由未添加OSA的0.61~0.63 μ L/cm2下降到0.50~0.54 μ L/cm2。分别以33.7和67.4 μ g/株剂量的草甘膦点叶处理空心莲子草,发现添加OSA的处理对再生植株茎叶生长的抑制率分别比对照提高了8.89%和14.83%。草甘膦(有效成分199.3 g/hm2)施药后1 h进行人工模拟降雨处理,添加OSA后药剂对空心莲子草的生物活性比无OSA对照处理提高了20.5%。研究结果表明,添加有机硅喷雾助剂促进了草甘膦在空心莲子草中的向下传导性能,提高了草甘膦水剂在空心莲子草叶片的耐雨水冲刷性能,但会降低草甘膦药液在空心莲子草上的最大稳定持留量。     

Metabolic and histological parameters of silver catfish (Rhamdia quelen) exposed to commercial formulation of 2,4-dichlorophenoxiacetic acid (2,4-D) herbicide

The objective of this study was to investigate the effects of commercial formulation of herbicide 2,4-D on metabolic parameters, acetylcholinesterase (AChE) activity and liver histological evaluation of silver catfish (Rhamdia quelen) exposed for 96 h. AChE activity increased in brain (600 and 700 mg L⁻¹) and decreased in all concentrations tested in muscle tissue. Hepatic glycogen was reduced after 2,4-D exposure ranging from 47.67% (400 mg L⁻¹) until 59.3% (700 mg L⁻¹). Hepatic tissue showed lactate reduction at all 2,4-D concentrations tested and glucose was reduced only at 700 mg L⁻¹. In the highest concentration tested hepatic glycogen and glucose reduced instead plasma glucose levels increased. White muscle tissue showed glycogen reduction in fingerlings exposed to all herbicide concentrations and glucose reduction at 700 mg L⁻¹. Muscle lactate levels increase at all 2,4-D concentrations tested. Vacuolation of hepatocytes and changes in its arrangement cords were observed by histologic analysis in group treated with 700 mg/L of 2,4-D. These results suggest that silver catfish exposed to concentrations of 2,4-D near of CL₅₀ showed metabolic and histological response to compensate some stress caused by herbicide exposure. Taken together parameters measured can be used as biomarkers to monitor herbicide contaminated water.     

Investigation of acute toxicity of (2,4-dichlorophenoxy)acetic acid (2,4-D) herbicide on crayfish (Astacus leptodactylus Esch. 1823)

The acute 96 h LC₅₀ of (2,4-dichlorophenoxy)acetic acid (2,4-D), a widely used agricultural herbicide, was determined on crayfish (Astacus leptodactylus Esch. 1823). Crayfish of 23.5 ± 1.49 g mean weight and 9.6 ± 0.21 cm mean length were selected for the bioassay experiments. The experiments were repeated three times, in 10 L tap water. The data obtained were statistically evaluated by the use of the E.P.A computer program based on Finney’s probit analysis method and the 96 h LC₅₀ value for crayfish was calculated to be 32.6 mg/L in a static bioassay test system. 95% lower and upper confidence limits for the LC₅₀ were 15.10-327.16. In conclusion, 2,4-D is highly toxic to crayfish, a non-target organism in the ecosystem. Water temperature was 23 ± 1 °C. Behavioral changes of crayfish were recorded for all herbicide concentrations.     

Biotransformation of clomazone in rice (Oryza sativa) and early watergrass (Echinochloa oryzoides)

Rice (Oryza sativa), a relatively tolerant species, and early watergrass (Echinochloa oryzoides; EWG), a relatively susceptible species, were exposed to ¹⁴C-labeled clomazone to determine accumulation, biotransformation, and mass balance. On a total mass basis, rice absorbed more clomazone than EWG (p < 0.05), but on a nmol/g basis, there was no significant difference between the two species (p > 0.05). Rice contained more extractable ¹⁴C residues (7.7 ± 0.5 vs. 4.8 ± 0.5 nmol in rice vs. EWG, respectively; p < 0.5), but the concentration in EWG was significantly higher (4.2 ± 0.5 vs. 1.8 ± 0.1 nmol/g in EWG vs. rice, respectively; p < 0.01). More metabolized residue was measured in EWG compared to rice (84.1% vs. 67.9%; p < 0.01). Both species produced hydroxylated forms, β-d-glucoside conjugates, and several other unidentified polar metabolites, but EWG generally produced higher metabolite concentrations. The concentration of the suspected active metabolite, 5-ketoclomazone, was significantly higher in EWG vs. rice (21 ± 2 vs. 5.7 ± 0.5 pmol/g, respectively; p < 0.01). Differences in sensitivity to clomazone between rice and EWG appear to be due to differential metabolism, but in this case the more susceptible EWG qualitatively and quantitatively metabolized more clomazone than the more tolerant rice. This is consistent with the action of a metabolically activated herbicide. This metabolic difference could be exploited to develop herbicide safeners for use with clomazone.     

Effects of the organophosphate pesticide Folidol 600® on the freshwater fish, Nile Tilapia (Oreochromis niloticus)

Nile Tilapia (Oreochromis niloticus) juveniles were exposed to different concentrations of Folidol 600® in static toxicity tests. The 24, 48, 72 and 96 h LC₅₀ values of Folidol 600® to O. niloticus were 17.82, 8.91, 4.00 and 2.70 mg L⁻¹, respectively. The values of hematological parameters increased, and inhibition of cholinesterases activity (AChE, BChE and PChE) in plasma of fish exposed to the higher concentrations of pesticide reached 94%. Furthermore, the exposure of Tilapia to Folidol 600® caused an increase of 4%, 20% and 38.4% in oxygen consumption at 0.1, 0.5 and 1.0 mg L⁻¹, respectively. However, exposure to 2.5, 5.0 and 10 mg L⁻¹ caused a decrease of 33.6%, 35.2% and 42.4% in oxygen consumption relative to the control. The ammonium excretion of fish exposed to 0.0, 0.1, 0.5, 1.0, 2.5, 5.0 and 10.0 mg Folidol 600®/L was 0.12, 0.18, 0.30, 0.33, 0.37, 0.36 and 0.33 μg/g/min, i.e., 50%, 150%, 175%, 208%, 200% and 175% increase, respectively, relative to the control.     

Leaf tissue pigments and chlorophyll fluorescence parameters vary among sweet corn genotypes of differential herbicide sensitivity

Herbicide applications are meant to eliminate weed competition; however, herbicides may also impose abiotic stress on registered crops. Leaf tissue carotenoid pigments play vital roles in the photoprotection of photosynthetic membranes and contribute to non-photochemical quenching (NPQ) of excitation energy, both important to plant environmental stress tolerance. Our research objectives were to characterize leaf tissue pigments and chlorophyll fluorescence parameters following post-emergence herbicide applications (simulating an abiotic stress) to sweet corn (Zea mays var. rugosa) genotypes of differential herbicide sensitivities. Post-emergence herbicide applications of combinations of mesotrione (105 g ai/ha) and atrazine (560 g ai/ha) were applied to ‘Merit’ (sensitive), ‘Temptation’ (tolerant), and ‘Incredible’ (moderately sensitive) sweet corn genotypes. Leaf tissues were sampled after herbicide applications and measured for chlorophyll fluorescence parameters, and the same tissues were analyzed for carotenoid and chlorophyll pigments. Leaf pigments and chlorophyll fluorescence were not affected by any herbicide treatment; however, data revealed significant differences between genotypes for leaf tissue antheraxanthin, β-carotene, zeaxanthin, chlorophyll a/b ratios, and for values of F_o, F_m, F_v, and NPQ, with ‘Merit’ leaf tissue having higher values than the other two genotypes evaluated. Results demonstrate that genotypic sensitivities to certain post-emergence herbicides may be related to concentrations of photo-protective carotenoids in sweet corn leaf tissues.     

Glyphosate efficacy is contributed by its tissue concentration and sensitivity in velvetleaf (Abutilon theophrasti)

Glyphosate efficacy was examined in young velvetleaf plants from the standpoint of its tissue distribution and sensitivity. In whole plant assays, manual application of a sub-lethal dose to the first leaf resulted only in meristem injury while other tissues remained visually healthy. Our studies showed that this differential tissue response was caused by a combination of differential distribution as well as sensitivity to glyphosate. Using [¹⁴C]glyphosate, we measured tissue injury and glyphosate residue, and calculated tissue threshold for 50% growth inhibition. Our studies showed that roots and meristem have high glyphosate distribution (45 and 34% of translocated, respectively) and low inhibition thresholds (0.23 and 0.21 ppm, respectively) resulting in tissues that were easily killed by glyphosate. In contrast, the base stem contained a much higher inhibition threshold (8.4 ppm) with only intermediate distribution (10%) resulting in a tissue that was most difficult to kill. We observed a linear relationship between glyphosate dose and tissue concentration; furthermore, tissue distribution pattern was independent of dose or surfactants class. At a sub-lethal dose, sensitive tissues that received a large distribution of glyphosate were preferentially killed. As the dose was increased, more glyphosate was available for distribution, and all tissues received a proportionately greater amount of glyphosate. Plant death occurred when the applied dose was sufficient to attain the lethal threshold in all tissues.     

Effect of herbicides and doses on short- and long-term control of Eleusine tristachya

In Argentina, Eleusine tristachya has been recently reported as a problematic weed that can occur at high densities in spring and summer in fallows and in maize and soyabean. The reason for the increase in E. tristachya populations is that once the weed is established, it is difficult to eliminate because it produces a high number of seeds and plant regrowth occurs after herbicide treatments. The aim of this study was to determine the effect of post-emergence application of herbicides (glyphosate, haloxyfop-methyl and clethodim) at the seedling, vegetative and reproductive stages on the short-term (biomass 30 days after treatment—30 DAT) and long-term (tiller number and height and seed production—regrowth at 330 DAT) control of E. tristachya selected biotypes in outdoor pot experiments. Data fitted to a log-logistic model. For all the herbicides considered, at the seedling and vegetative stages, short-term control was achieved with low ED₅₀ and ED₉₀ values, whereas at the reproductive stage, ED₉₀ values were three- to sixfold (glyphosate), six- to 52-fold (haloxyfop-methyl) and five- to 13-fold (clethodim) higher. Long-term control at the recommended dose or lower was not possible at the reproductive stage as tiller regrowth and seed production occurred with all herbicides. It is advisable to control Eleusine tristachya when plants are small at the beginning of the growing season using the recommended herbicide dose. A delayed application will produce tiller regeneration the following year, and consequently, control would only be achieved applying an overdose, which can cause risks to health and the environment. We concluded that a management programme based on the combination of glyphosate with post-emergence graminicides applied at early stages will be effective to control future infestations.     

Some physicochemical factors influencing foliar uptake enhancement of glyphosatemono(isopropylammonium) by polyoxyethylene surfactants

Structure-concentration–foliar uptake enhancement relationships between commercial polyoxyethylene primary aliphatic alcohol (A), nonylphenol (NP), primary aliphatic amine (AM) surfactants and the herbicide glyphosatemono(isopropylammonium) were studied in experiments with wheat (Triticum aestivum L.) and field bean (Vicia faba L.) plants growing under controlled-environment conditions. Candidate surfactants had mean molar ethylene oxide (EO) contents ranging from 5 to 20 and were added at concentrations varying from 0·2 to 10 g litre^?-1 to [¹⁴C]glyphosate formulations in acetone–water. Rates and total amounts of herbicide uptake from c. 0·2–μl droplet applications of formulations to leaves were influenced by surfactant EO content, surfactant hydrophobe composition, surfactant concentration, glyphosate concentration and plant species, in a complex manner. Surfactant effects were most pronounced at 0·5 g acid equivalent (a.e.) glyphosate litre^?-1 where, for both target species, surfactants of high EO content (15–20) were most effective at enhancing herbicide uptake: surfactants of lower EO content (5–10) frequently reduced, or failed to improve, glyphosate absorption. Whereas, at optimal EO content, AM surfactants caused greatest uptake enhancement on wheat, A surfactants gave the best overall performance on field bean; NP surfactants were generally the least efficient class of adjuvants on both species. Threshold concentrations of surfactants needed to increase glyphosate uptake were much higher in field bean than wheat (c. 2 g litre^?-1 and < 1 g litre^?-1, respectively); less herbicide was taken up by both species at high AM surfactant concentrations. At 5 and 10 g a.e. glyphosate litre^?-1, there were substantial increases in herbicide absorption and surfactant addition could cause effects on uptake that were different from those observed at lower herbicide doses. In particular, the influence of EO content on glyphosate uptake was now much less marked in both species, especially with AM surfactants. The fundamental importance of glyphosate concentration for its uptake was further emphasised by experiments using formulations with constant a.i./surfactant weight ratios. Any increased foliar penetration resulting from inclusion of surfactants in 0·5 g litre^?-1 [¹⁴C]glyphosate formulations gave concomitant increases in the amounts of radiolabel that were translocated away from the site of application. At these low herbicide doses, translocation of absorbed [¹⁴C]glyphosate in wheat was c. twice that in field bean; surfactant addition to the formulation did not increase the proportion transported in wheat but substantially enhanced it in field bean.     

Cytogenetic effects of commercially formulated atrazine on the somatic cells of Allium cepa and Vicia faba

In the present study cytogenetic effects of atrazine herbicide, were examined on the root meristem cells of Allium cepa and Vicia faba. Test concentrations were chosen by calculating EC₅₀ values of formulated atrazine against both the test systems which determined to be 30 mg l⁻¹ for A. cepa and 35 mg l⁻¹ for V. faba, respectively. For cytogenetic effects root meristem cells of A. cepa were exposed to 15, 30 or 60 mg l⁻¹ whereas V. faba to 17.5, 35 or 70 mg l⁻¹ for 4 or 24 h. Roots exposed for 4 or 24 h, after sampling, were left in water for 24 h recovery and sampled at 24 h post-exposure. A set of onion bulbs or seedlings of V. faba exposed to DMSO (0.3%) was run parallel for negative control. Treatment of atrazine significantly and dose-dependently inhibited the mitotic index (MI) and induced micronucleus formation (MN) chromosome aberrations (CA) and mitotic aberrations (MA) in both the test systems at 4 or 24 h. Root meristem cells examined at 24 h post-exposure also revealed significant (p < 0.001) frequencies of MN, CA or MA despite considerable decline. Chromosome breaks and fragments were found to be major CA whereas C-metaphase, chromosome bridges and laggards were prevalent MA. Results of our study, indicate that atrazine may produce genotoxic effects in plants. Further, both the plant bioassays found to be sensitive indicators for the genotoxicity assessment as the outcome of majority of in vivo/in vitro mammalian tests are comparable.     

Green nanoemulsion‐laden glyphosate isopropylamine formulation in suppressing creeping foxglove (A. gangetica), slender button weed (D. ocimifolia) and buffalo grass (P. conjugatum)

BACKGROUND: Pesticides are developed with carriers to improve their physicochemical properties and, accordingly, the bioefficacy of the applied formulation. For foliar‐applied herbicide, generally less than 0.1% of the active ingredient reaching the target site could reduce pesticide performance. Recently, a carrier of nanoemulsion consisting of oil, surfactant and water, with a particle size of less than 200 nm, has been shown to enhance drug permeability for skin penetration in pharmaceutical delivery systems. In the present work, the aim was to formulate a water‐soluble herbicide, glyphosate isopropylamine (IPA), using a green nanoemulsion system for a biological activity study against the weeds creeping foxglove, slender button weed and buffalo grass. RESULTS: The nanoemulsion formulations displayed a significantly lower spray deposition on creeping foxglove (2.9–3.5 ng cm^?2), slender button weed (2.6–2.9 ng cm^?2) and buffalo grass (1.8–2.4 ng cm^?2) than Roundup^® (3.7–5.1 ng cm^?2). The visible injury rates of weeds treated with the nanoemulsion formulations were statistically equivalent to those relating to Roundup^® at 14 days after treatment, with a control range of 86.67–96.67%. CONCLUSION: It was hypothesised that the significant difference in spray deposition with equal injury rates can be attributed to enhanced bioactivity of the nanoemulsion formulations. This initial discovery could be the platform for developing better penetration of agrochemical formulations in the future. Copyright © 2012 Society of Chemical Industry     

Insect Pests of Cotton – Western Herbaceum Region of India

Abstract

Pre-plant and pre-emergence herbicides were tested for effective weed control in a seed crop of okra during 1974–75 and 1975–76. All treatments significantly decreased the weed population and increased the seed yield as compared to the unweeded control. Fluchloralin (0.90 and 1.20 kg a.i./ha pre-plant), alachlor (2.50 kg a.i./ha pre-em) and EPTC plus alachlor (3.75 kg a.i./ha pre-plant and 1.25 kg a.i./ha pre-em) proved to be the most effective and economical treatments. No residual effects were observed with any herbicide on the succeeding crops of radish, carrot, turnips, peas and spinach.     

Protoporphyrinogen IX-oxidizing activities involved in the mode of action of a new compound N-[4-chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide

N-[4-Chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide (EK-5385) is an experimental substituted bicyclic herbicide. Soil-applied EK-5385 showed good rice selectivity and potent herbicidal activity on barnyardgrass (Echinochloa crus-galli var. oryzicola) at rates of 3.9-250 g a.i./ha. Barnyardgrass was exhibited normal growth under dark condition, however, the growth of shoot and root was severely inhibited under light condition (14/10 h of light/dark, 50 μmol/m²/s of photosynthetically active radiation) when treated with EK-5385, oxadiazon, and oxadiargyl. IC₅₀ of EK-5385 and oxadiargyl to chlorophyll loss in cucumber cotyledons was approximately 0.3 and 0.7 μM, respectively. IC₅₀ of EK-5385 and oxadiargyl to carotenoids loss in cucumber cotyledons was about 0.26 and 0.1 μM, respectively. IC₅₀ concentration of EK-5385 and oxadiargyl on Protox activity was approximately 5.5 and 8 nM, respectively. Cellular leakage occurred without lag period from cucumber leaf squares treated with 1 μM of EK-5385 and oxadiargyl under light exposure.     

In vitro and in vivo effects of some pesticides on carbonic anhydrase enzyme from rainbow trout (Oncorhynchus mykiss) gills

Here we investigated the in vitro and in vivo effects of the pesticides, deltamethrin, diazinon, propoxur and cypermethrin, on the activity of rainbow trout (rt) gill carbonic anhydrase (CA). The enzyme was purified from rainbow trout gills using Sepharose 4B-aniline-sulfanilamide affinity chromatography method. The overall purification was approx. 214-fold. SDS-polyacrylamide gel electrophoresis showed a single band corresponding to a molecular weight of approx. 29 kDa. The four pesticides dose-dependently inhibited in vitro CA activity. IC₅₀ values for deltamethrin, diazinon, propoxur and cypermethrin were 0.137, 0.267, 0.420 and 0.460 μM, respectively. In vitro results showed that pesticides inhibit rtCA activity with rank order of deltamethrin > diazinon > propoxur > cypermethrin. Besides, in vivo studies of deltamethrin were performed on CA activity of rainbow trout gill. rtCA was significantly inhibited at three concentrations (0.25, 1.0 and 2.5 μg/L) at 24 and 48 h.     

Efficacy and fate of glyphosate on Swedish railway embankments

The herbicide glyphosate, N-(phosphonomethyl)glycine, as Spectra (240 g AI litre(-1) SL; Monsanto Europe AB), RoundUp (360 g AI litre(-1) SL; Monsanto) and RoundUp Bio (360 g AI litre(-1) SL; Monsanto), have been used for weed control on Swedish railway embankments since 1986. This article summarizes results from studies of the weed effect and behaviour of glyphosate for the period 1984-2003. Studies on a railway embankment with a range of application rates showed excellent weed control at 5 litre ha(-1) of RoundUp Bio. The appearance of glyphosate and its metabolite AMPA [(aminomethyl)phosphonic acid] in the embankment, eg mobility and persistence, was also studied. Mobility was low in most cases, the main proportion of both glyphosate and AMPA being found in the upper 30-cm layer although minor amounts penetrated to lower depths. The 50% disappearance time of glyphosate was generally <5 months in railway embankments but cases with longer persistence were found. Transport to the groundwater was observed for glyphosate and AMPA in groundwater pipes along tracks. Downward transport appears to be dependent on the application rate, which should not exceed 3 litre ha(-1) of RoundUp Bio to avoid groundwater contamination. A lower rate of glyphosate mixed with a low rate of another herbicide may achieve acceptable weed control and be environmentally safer.     

Effects of Artemisia annua L. (Asteracea) on nutritional physiology and enzyme activities of elm leaf beetle, Xanthogaleruca luteola Mull. (Coleoptera: Chrysomellidae)

Methanolic extract of Artemisia annua L., a weed collected around paddy fields in north of Iran, was investigated for its toxic effects on: feeding, growth, fecundity, fertility including the biochemical characteristics of elm leaf beetle Xanthogaleruca luteola Mull. The toxicity tests indicate that insecticidal effect was 2.4-fold higher in 3rd instar larvae than in adults. The LC₅₀ was 48% and 43.77% of a methanolic leaf extract at 24 and 48 h, respectively. The feeding deterrence was highest at 10% concentration and lowest at 0.625% for 3rd instar larvae and adults during the first 24 h and decreased thereafter. Larval duration significantly increased at higher concentrations. Larval treatment with 10% methanolic extract resulted in deformed adults (adultoids) with drastic changes in gross morphology of female reproductive system. Food digestion and assimilation significantly decreased in adults. Larval duration and adult fecundity and fertility were also significantly reduced. Twenty-four hours after treating 3rd instar larva with the extract the levels of glucose, protein, urea, uric acid, α-amylase, alkaline phosphatase, alanine amino transferase and aspartate amino transferase significantly changed. However, at 48 h the extract lost its potency. The extract did not effect the level of cholesterol in treated larva. These results indicate that Artemisia annua L. extract contains inhibitors of key metabolic pathways that may be useful in future control of the elm leaf beetle.     

Sensor‐based assessment of herbicide effects

Non‐destructive assessment of herbicide effects may be able to support integrated weed management. To test whether effects of herbicides on canopy variables could be detected by sensors, two crops were used as models and treated with herbicides at BBCH 20 using a logarithmic sprayer. Twelve days after spraying at BBCH 25 and 42 days after sowing, nine sensor systems scanned a spring barley and an oilseed rape field experiment sown at different densities and sprayed with increasing field rates of glyphosate and tribenuron‐methyl. The objective was to compare ED₅₀s for crops and weeds derived by the different sensors in relation to crop density and herbicides. Although sensors were not directly developed to detect herbicide symptoms, they all detected changes in canopy colours or height and crop density. Generally ED₅₀s showed the same pattern in response to crop density within herbicide, but there were marked differences between barley and oilseed rape. We suggest that the results of comparing the various sensor outputs could become a stepping stone to future standardisation for the benefit of the research and development of sensors that will detect herbicide effect on crops and weeds, particularly at the most vulnerable stages of development of the canopy.