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Durante 1986-89 se llevó a cabo un estudio de campo en la Subestación de Lajas para evaluar los herbicidas registrados ametryn, diuron, asulam, hexazinone (Velpar) y metribuzin y los no registrados terbutryn, pendimethalin e imazapyr para controlar la yerba peluda (Roftboellia exaltata) en caña de azúcar en cultivos sucesivos de plantilla y primer retoño. Imazapyr, pendimethalin, terbutryn y ametryn a las dosis recomendadas de 0.28, 1.78, 2.69 y 4.49 kg/ha. controlaron la yerba peluda con efectividad comparable al desyerbo a mano en caña de plantilla. En el retoño todos los herbicidas usados demostraron una efectividad mayor debido, posiblemente, a una menor población del yerbajo. El herbicida imazapyr causó fitotoxicidad a las plántulas de caña, la cual fue más severa en el retoño. Las parcelas tratadas con los herbicidas mencionados produjeron rendimientos de azúcar por hectárea para la plantilla entre 14.92 y 17.02 toneladas comparables estadísticamente con el tratamiento de desyerbo a mano (17.5 tons/ha.), pero superiores significativamente a los de tratamientos de diuron, asulam y el testigo sin desyerbo. La producción de azúcar por ha. para el retoño siguió más o menos el mismo patrón que en la plantilla, excepto que las parcelas tratadas con asulam y diuron produjeron más y las tratadas con imazapyr y ametryn produjeron menos. La producción combinada de azúcar de la plantilla y el retoño en el tratamiento con pendimethalin fue estadísticamente igual que para el desyerbo a mano, pero solo significativamente superior a hexaxinone, imazapyr y el tratamiento sin desyerbar.

Seven algal species were used to conduct toxicity assays with 12 herbicides to determine differences in species sensitivity. A fluorescence microplate toxicity assay was used as an efficient and economical high-throughput assay. The obtained toxicity data were standardized based on the species sensitivity distribution concept. The most-sensitive individual species differed among herbicides: Desmodesmus subspicatus was most sensitive to chloronitrofen and pendimethalin; Achnanthidium minutissimum was most sensitive to chlorpropham; Nitzschia palea was most sensitive to diquat, glyphosate, and dichlobenil; Navicula pelliculosa was most sensitive to trifluralin; and Pseudanabaena foetida was most sensitive to glufosinate, asulam, and 2,4-D. Surprisingly, Raphidocelis (formerly Pseudokirchneriella) subcapitata, a standard green alga, was not the most sensitive to any of the herbicides. The results clearly showed that a single algal species cannot represent the algal assemblage in terms of sensitivity. Therefore, multispecies algal toxicity data sets are essential for assessing the ecological effect of herbicides.

Herbicides are vital for modern agriculture, but their utility is threatened by genetic or metabolic resistance in weeds as well as heightened regulatory scrutiny. Of the known herbicide modes of action, 6-hydroxymethyl-7,8-dihydropterin synthase (DHPS) which is involved in folate biosynthesis, is targeted by just one commercial herbicide, asulam. A mimic of the substrate para-aminobenzoic acid, asulam is chemically similar to sulfonamide antibiotics – and while still in widespread use, asulam has faced regulatory scrutiny. With an entire mode of action represented by just one commercial agrochemical, we sought to improve the understanding of its plant target. Here we solve a 2.6 Å resolution crystal structure for Arabidopsis thaliana DHPS that is conjoined to 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) and reveal a strong structural conservation with bacterial counterparts at the sulfonamide-binding pocket of DHPS. We demonstrate asulam and the antibiotics sulfacetamide and sulfamethoxazole have herbicidal as well as antibacterial activity and explore the structural basis of their potency by modelling these compounds in mitochondrial HPPK/DHPS. Our findings suggest limited opportunity for the rational design of plant selectivity from asulam and that pharmacokinetic or delivery differences between plants and microbes might be the best approaches to safeguard this mode of action.

Sugarcane growers in Florida have been reporting reduced control of fall panicum with asulam, the main herbicide used for POST grass control. Therefore, outside container experiments were conducted to determine the response of four fall panicum populations from Florida to asulam applied alone and to evaluate whether tank-mix combination with trifloxysulfuron enhances control. Asulam was applied at 230 to 7,400 g ai ha−1, corresponding to 1/16 to 2X the maximum labeled rate for a single application in sugarcane, with or without combination with trifloxysulfuron at 16 g ai ha−1. Three fall panicum populations were collected from fields in which reduced control had been reported, while one population was from a field not used for sugarcane production but adjacent to a sugarcane field. The potency of asulam based on ED50values (the rate required to cause 50% dry weight reduction at 28 d after treatment) ranged from 2,249 to 5,412 g ha−1for tolerant populations with reported reduced fall panicum control compared with 1,808 g ha−1for the susceptible population from the field not used for sugarcane production, showing that the latter was most sensitive to asulam. Addition of trifloxysulfuron to asulam increased potency on fall panicum by 5- to 15-fold, indicating that the tank mix enhanced dry weight reduction for all populations. The probability of fall panicum survival (regrowth after aboveground biomass harvesting) at the labeled rate of asulam ranged from 2% to 47% compared with 0% to 6% when trifloxysulfuron was added to the tank mix. Our results show differential response of fall panicum populations in Florida to asulam, which can be overcome by tank mixing with trifloxysulfuron even for populations that are difficult to control in sugarcane, but no evolution of resistance to asulam.

Inspired by the photoelectrochemical (PEC) properties of TiO2 nanotubes arrays (TNA) and their application as a super vessel for immobilizing biomolecules, we constructed an inhibition-effect PEC biosensor for determination of asulam based on the in-situ generation of CdS quantum dots (QDs) on TNA using an enzymatic reaction. Horseradish peroxidase (HRP) enzyme was covalently assembled on the inner-wall of TNAs, which exhibited good electrochemical and catalytic properties. In the mixture solution containing H2O2, CdY and S2O32-, HRP enzyme in TNAs catalyzed H2O2 reduce S2O32- to S2-. The generated S2- reacted with CdY to form CdS QDs in situ on the TNAs, improving the PEC performance of TNA under visible light irradiation. The photocurrent would decrease after addition of asulam due to its inhibitory effect towards HRP enzyme activity. Under the optimal experimental conditions, the constructed PEC TNA/HRP biosensor exhibited a satisfying linear range (0.02–2.0 ng mL−1), low limit of detection (4.1 pg mL−1) and good selectivity towards asulam determination, and has been successfully applied for the analysis of real environmental water samples with good accuracy of the recoveries ranged from 90% to 114%.

This study was performed to find the effective post-emergence herbicides to control of Poa annua that has already emerged from the soil in Kentucky bluegrass. A total of 8 treatments consist of various post- emergence herbicides applied at recommended concentration or lower concentration than recommended concentration to prevent Kentucky bluegrass injury in this study. Methiozolin showed the least injury in Kentucky bluegrass during 40 days after treatments and there were no footprints by methiozolin in creeping bentgrass green during 20 days. However, Poa annua control was 60.4%, which was less than those of other 7 treatments in this study. Both of asulam sodium and iodosulfuron plus asulam sodium exhibited the higher Poa annua control of 81.7% and 82.2% respectively without serious injury in Kentucky bluegrass during 40 days, and they showed a slight footprints damage in creeping bentgrass green. On the other hand, critical Kentucky bluegrass injuries and the vivid and numerous footprints were occurred in treatments of trifloxysulfuron-sodium, foramsulfuron, rimsulfuron and flazasulfuron, even though they were applied with only 1/4 of recommended concentration. Methiozolin is available to reduce gradually Poa annua population on Kentucky bluegrass without severe turfgrass damage. Asulam sodium or iodosulfuron plus asulam sodium could be useful to remove Poa annua by spot treatment but it is prohibited to spray directly on green even spot.

Elephantgrass has been proposed as a potential feedstock for biofuel production in south Florida. To limit future invasion of escapes in sugarcane and vegetables, the response of newly established elephantgrass to glyphosate, clethodim, sethoxydim, asulam, and trifloxysulfuron was determined using dose–response curves. Log-logistic models were used to determine the herbicide dose required to produce 90% growth reduction (GR90). The GR90values for shoot biomass at 21 d after treatment (DAT) were 477 g ae ha−1of glyphosate, 262 g ai ha−1of clethodim, 381 g ai ha−1of sethoxydim, 12 kg ai ha−1of asulam, and 94 g ai ha−1of trifloxysulfuron. The GR90values for root biomass at 35 DAT were 570 g ae ha−1of glyphosate, 257 g ai ha−1of clethodim, 432 g ai ha−1of sethoxydim, 17 kg ai ha−1of asulam, and 183 g ai ha−1of trifloxysulfuron. Elephantgrass was predicted to exhibit 97, 98, 75, 1, and 5% mortality after application of glyphosate, clethodim, sethoxydim, asulam, and trifloxysulfuron, respectively, at the label use rates 35 DAT. Results suggest that glyphosate and clethodim will provide control of newly established elephantgrass at label use rates for spot treatments and in vegetables, respectively. Rates higher than the label use rate of sethoxydim will be required to provide acceptable control of newly established elephantgrass in vegetables. However, newly established elephantgrass was not controlled by asulam and trifloxysulfuron at label use rates, implying that control of escapes will be difficult in sugarcane.

There is a need for management strategies to control dominant perennial weeds and restore seminatural communities. We compared the effects of five weed control treatments on dense Pteridium aquilinum relative to an untreated experimental control over an 8‐year period with the aim of restoring acid grassland. The weed control treatments tested were as follows: cutting and bruising, both twice and thrice annually, and herbicide treatment (asulam in year 1 followed by annual spot retreatment of all emergent fronds). Pteridium aquilinum performance and plant species composition were monitored. Data were analysed using Bayesian mixed‐effect models and multivariate techniques. Cutting twice and thrice yearly and the asulam treatment all reduced frond density to zero; both bruising treatments were ineffective. The plant communities in the cut and asulam‐treated plots showed differences from the untreated and bruised plots; the asulam‐treated plots contained more ruderal species and the cut plots were more typical of acid grassland. Acid grassland recovery was fastest in the asulam‐treated plots, but the cut plots caught up after approximately 5 years. There were two important conclusions. First, an intractable weed like P. aquilinum can be eradicated and a vegetation more suited for grazing can be achieved by the continuous application of some treatments over many years. Here, success was achieved by cutting twice/thrice annually, or by a single asulam application followed by annual spot spraying of all emergent fronds for 8 years. Second, bruising, a treatment favoured by some conservation organisations, did not work and cannot be recommended. The use of long‐term, continuously applied treatments might be considered for all perennial weeds with large underground root/rhizome systems.

In this study, we attempted to control invaded hetero-species turfgrass in golf courses with herbicides. Asulam sodium SP and trifloxysulfuron-sodium WG (to control creeping bentgrass in zoysiagrass), trifloxysulfuron-sodium WG (to control kentucky bluegrass in zoysiagrass), and mesotrione SC (to control creeping bentgrass in kentucky bluegrass) were selected as efficient herbicides. To creeping bentgrass, asulam sodium SP and trifloxysulfuron-sodium WG until 70 days after application (DAA), mesotrione SC until 230 DAA and to kentucky bluegrass trifloxysulfuron-sodium WG until 110 DAA; the applications showed 90% herbicidal effect. At 4 X recommended application dose, asulam sodium SP, trifloxysulfuronsodium WG (to zoysiagrass) and mesotrione (to kentucky bluegrass) showed insignificant harmful effect. With recommended dose, asulam sodium SP showed 80% control effect of creeping bentgrass in zoysiagrass until 40 DAA and trifloxysulfuron-sodium WG demonstrated 85% control efficiency until 30 DAA. Trifloxysulfuron-sodium WG controlled 85% of kentucky bluegrass in zoysiagrass until 40 DAA. Mesotrione SC with recommended dose showed 95% control efficiency to creeping bentgrass in kentucky bluegrass.

Giant reed has been proposed as a bioenergy crop in the sugarcane production region of south Florida, where it has a high invasive potential. In an effort to limit future invasion of giant reed escapes in sugarcane, currently labeled sugarcane herbicides asulam and trifloxysulfuron were evaluated for its management. Greenhouse and field dose–response studies were conducted at the Everglades Research and Education Center in Belle Glade, FL, between 2010 and 2011. Herbicides were applied at rates ranging from 0.46 to 7.4 kg ha−1asulam and 2 to 32 g ha−1trifloxysulfuron, which represent 0.125× to 2× sugarcane labeled use rates, respectively. In the greenhouse, asulam and trifloxysulfuron reduced giant reed relative shoot dry weight by a maximum of 50% at 21 d after treatment (DAT). The probability of giant reed resprouting 35 d following herbicide treatment was greater for trifloxysulfuron when compared with asulam. In the field, it was predicted that a maximum of 69 and 55% giant reed control occurred with application of asulam and trifloxysulfuron, respectively, at 14 DAT. Relative shoot dry weight of giant reed treated with asulam and trifloxysulfuron was reduced by a maximum of 43% at 42 DAT. Application of asulam and trifloxysulfuron did not provide complete control of giant reed at twice the labeled sugarcane use rate, indicating that control of established giant reed in sugarcane with currently available herbicides would not be an option.

It is necessary to control root parasitic weeds before or as they attach to the crop. This can only be easily achieved chemically with herbicides that are systemic, or with herbicides that are active in soil. Long-term control can only be attained if the crops do not metabolise the herbicide, i.e. have target-site resistance. Such target-site resistances have allowed foliar applications of herbicides inhibiting enol-pyruvylshikimate phosphate synthase (EPSPS) (glyphosate), acetolactate synthase (ALS) (e.g. chlorsulfuron, imazapyr) and dihydropteroate synthase (asulam) for Orobanche control in experimental conditions with various crops. Large-scale use of imazapyr as a seed dressing of imidazolinone-resistant maize has been commercialised for Striga control. Crops with two target-site resistances will be more resilient to the evolution of resistance in the parasite, if well managed.

The variability in the success of Pteridium aquilinum (bracken) control and vegetation restoration has been highlighted as a major issue in the United Kingdom. Experiments were set up at four different regional locations to assess bracken control at the national scale and the impact of restoration practices at the local scale. Bracken control treatments (cutting once or twice per year, a combination of cutting and asulam spraying, and asulam in year 1) were combined with site-specific treatments designed to restore appropriate heathland or acid grassland vegetation. This article considers the effects on the developing understorey vegetation, testing the following hypotheses: (1) local differences between sites would affect community change; (2) treatments applied to control Pt. aquilinum (same at all sites) influences community change; and (3) treatments applied at the individual site level to restore vegetation influences community change toward the target vegetation. There were a considerable number of spatial effects. It is, therefore, difficult to develop a one-size-fits-all policy for vegetation restoration within a national Pt. aquilinum control strategy. Few bracken control treatment effects were found, and, where they were detected, it was only at single sites. Thus, the development of target vegetation requires a combination of control and restoration treatments that take into consideration the aspects of that site. Only three species, Deschampsia flexuosa, Galium saxatile, and Campylopus introflexus, increased as a direct effect of the control treatments. Vegetation restoration was most successful in the cutting-twice-per-year plots, the treatment with the greatest reduction in Pt. aquilinum cover.

It has been suggested that trifloxysulfuron might increase the efficacy of asulam for control of johnsongrass. Container and field studies were conducted to determine the efficacy of POST applications of trifloxysulfuron and asulam for johnsongrass control in sugarcane. Asulam was applied at 460 and 920 g ai/ha to container-grown johnsongrass plants, with and without 8 g ai/ha of trifloxysulfuron. Combinations of asulam and trifloxysulfuron generally reduced johnsongrass height, rhizome length, and biomass more than when either was applied alone. Results suggested that combinations of asulam and trifloxysulfuron were synergistic in their control of johnsongrass biomass 8 wk after treatment. In a sugarcane field heavily infested with rhizome johnsongrass, asulam was applied at 1,800, 2,800, and 3,700 g/ha with and without trifloxysulfuron at 16 g/ha. Asulam plus trifloxysulfuron generally controlled johnsongrass more effectively than either herbicide alone. The control of johnsongrass with asulam at 1,800 g/ha resulted in an increase in sugar yield of more than twice that in the nontreated control. Sugar yield increased further when asulam was applied at 2,800 g/ha or combined with trifloxysulfuron, but application of trifloxysulfuron alone did not increase yield. Combinations of asulam and trifloxysulfuron might slow the spread of rhizome johnsongrass enough to allow an increased number of ratoon crops before sugarcane fields need to be replanted.

This paper describes the effectiveness of a range of bracken* control and heathland restoration treatments, in factorial combination, on heath development over an 18-year period. Control treatments included cutting once and twice yearly between 1978 and 1996: spraying the herbicide asulam at the recommended rate (4.4 kg a.i. ha -1 ) in two treatments. 1978 and 1978 plus 1979, each followed by repeat doses in 1984 and 1990: and spraying asulam followed by cutting once yearly. Calluna * seeds were added to half the plots to aid heathland establishment. After 6 years the experiment was split and bracken control was continued/re-applied on half the plots and stopped on the remainder. The effects of all treatments on the cover of colonizing species between 1986 and 1996 is described. Twenty-five species were recorded in the 10 years, but some were present only for a very short time. Initially Calluna establishment was good in some treatments. especially where Calluna seed was added and bracken was controlled ; cutting bracken twice yearly was most effective. Other plots developed either a grass heath flora dominated by Agrostis capillaris. Deschampsia flexuosa. Dicranum scoparium. Festuca ovina and Rumex acetosella, or were dominated by either Calamagrostis epigejos or Carex arenaria. Some plots were invaded by Betula spp.; mortality was high but some survived to overtop the bracken by 1996. In 1990 and 1991 there was considerable mortality of Rumex acetosella and Calluna, respectively, almost certainly as a direct effect of the weather: these 2 years were the hottest and driest during the experimental period. The grass heath species showed distinct spatial effects during colonization, and tended to have a greater cover where bracken control was continued. Bracken litter was maintained at a low cover where treatment was continued, but increased to near untreated levels within 10 years, except where bracken was cut twice yearly. The cut twice yearly plots started from a lower level, but litter cover was still increasing at the end of the experimental period. A major influence on the vegetation development was the increasing numbers of rabbits which occurred during the course of the experiment. Rabbits had invaded all treatments by 1996 and increased the amount of bare ground in many treatments. Rabbit activity was greatest where the bracken control was increased. The original objectives of the restoration scheme 'to restore a Calluna heathland' have not been met, as the Calluna died. However, a reasonable Breck grass heath flora developed in many plots, which is a better community from a conservation viewpoint than dense bracken. The implications for the restoration of heathland on dense bracken communities is discussed and an integrated management approach is suggested.

The coastal heathlands of north-western Europe are endangered habitats of great conservation value. Invasion by bracken Pteridium aquilinum is a major challenge for conservation and restoration of these heathlands, including the under-studied northern regions. Today, the herbicide asulam is the most widely applied bracken control measure, but increasing focus on organic farming and nature conservation calls for alternative, preferably mechanical, approaches. In a 7-year replicated field experiment in western Norway, we investigated efficiencies of the four bracken control measures asulam, Gratil, annual cutting and biannual cutting, in restoring the characteristic heathland vegetation structure and species composition. We specifically tested herbicide effects on diversity and composition of non-target species. Effects of treatments over time were evaluated by repeated measures ANOVA, and for multivariate data, Principal Response Curves. Our results show that UK based control methods are largely applicable to bracken at its northern limit in the European heathland habitat. Asulam resulted in the fastest reduction in cover but cutting proved equally efficient long-term. Community compositions progressed towards desired heathland vegetation, but successional trajectories differed. Asulam had unintended effects on a number of heathland species not predictable by species characteristics or functional groups. Gratil failed to have any long-term effects. In summary, cutting is as efficient as herbicide application in reducing bracken, and more so in restoring northern heathland vegetation over time.

Bracken (Pteridium aquilinum) is a major problem for livestock-based extensive agriculture, conservation, recreation, and game management globally. It is an invasive species often achieving dominance to the detriment of other species. Control is essential to maintain plant communities such as grassland and lowland heath or if extensive grazing by domestic stock, particularly sheep, is to be viable on upland margins. Bracken is managed primarily by herbicide application or cutting but other techniques including rolling, burning, and grazing are also utilized. Here we evaluate the evidence regarding the effectiveness of asulam for the control of bracken. Thirteen studies provided data for meta-analyses which demonstrate that application of the herbicide asulam reduces bracken abundance. Subgroup analyses indicate that the number of treatments had an important impact, with multiple follow-up treatments more effective than one or two treatments. Management practices should reflect the requirement for repeated follow-up. There is insufficient available experimental evidence for quantitative analysis of the effectiveness of other management interventions, although this results from lack of reporting in papers where cutting and comparisons of cutting and asulam application are concerned. Systematic searching and meta-analytical synthesis have effectively demonstrated the limits of current knowledge, based on recorded empirical evidence, and increasing the call for more rigorous monitoring of bracken control techniques. Lack of experimental evidence on the effectiveness of management such as rolling or grazing with hardy cattle breeds contrasts with the widespread acceptance of their use through dissemination of experience.

Questions: The objectives of this study were to assess the effect of Pteridium aquilinum (bracken) control treatments, at the national scale, and the impact of restoration practices, at the local scale, on P. aquilinum performance. Hypotheses: 1. Geographical location (locally between and within sites) affects the control of P. aquilinum through time. 2. Are the P. aquilinum control treatments successful at all sites, and if so which ones? 3. The treatments applied at the individual site level to restore vegetation influences the performance of P. aquilinum through time. Location: Four geographically distinct acid grassland and heathland sites infested with P. aquilinum across Great Britain. Methods: Six main-plot, bracken control treatments were applied to all sites with site-specific vegetation restoration treatments. Response variables (P. aquilinum cover, frond length and density) were monitored twice yearly, in June and August between 1993 and 2003. Results: Between- and within-site spatial ...

Summary Asulam was evaluated in three fields experiments for the control of Yorkshire fog (Holcus lanatus L.) in perennial rygrass(Lolium perenneL). It was used in 1976 on a 3 year-old ryegrass/timothy (Phleum pratense L.) sward in comparison with propyzamidc, in 1977 on a 9 year-old ryegrass pasture grazed at two stocking rates and in 1978 on an intensively managed ryegrass dominant sward. Asulam at 1.75 kg ha−1 gave good selective control in all the field experiments and was more effective under higher than lower slocking rates. In laxly grazed swards it was most effective when sprayed in October. Propyzamide also controlled H. lanatus and increased yields of while clover (Trifolium repens L.) even at 0.25 kg ha−1 but it damaged the sown grasses and increased the growth of broad-leaved weeds.

The systemic herbicide asulam is used extensively to control the weedy fern bracken ( Pteridium aquilinum (L.) Kuhn). Other ferns were thought to be highly sensitive to asulam exposure, but there has been a dearth of experimental evidence. Eight fern species were exposed to asulam spray at three different application rates or a control of water. Asulam was applied at the recommended field application rate for bracken clearance, and at two further rates corresponding to 10 and 50 m downwind of an aerial spray event. Damage was assessed over two seasons. All ferns tested were severely damaged by exposure to the highest application rate, but sensitivity varied between species. Maximum damage occurred 1 year after spraying, and limited signs of recovery could be seen by the second season. The effects of adding the adjuvant Agral® to applications of asulam were tested on the threatened pteridophyte Pilularia globulifera L. No damage additional to that caused by exposure to asulam was observed. This work supports the view that 50 m buffer zones are sufficient to protect sensitive ferns from the effects of aerial spraying with asulam, provided that drift-reducing nozzles are used and the manufacturer’s application guidelines are observed.

Bracken (Pteridium aquilinum) is a major weed of seminatural vegetation in Great Britain, as in many other countries. As a consequence, large areas have been subject to control with the intention of restoring the former vegetation. The use of aerial spraying with asulam, a narrow spectrum, carbamate herbicide, has become a common method of control. However, its long-term efficacy has not been assessed in terms of either controlling the bracken or in producing suitable restored habitats. This study undertook such an assessment by comparing the results of a 2002 survey of the sites subject to bracken control by aerial spraying of asulam with previous (1990/1991 and 1994) surveys of the same sites. This showed that a single application of asulam was effective in eradicating bracken ( 80%) and on the remainder it was still present in patches (>20% of quadrats), often at high density. More than half the sprayed sites had seen good recovery of moorland vegetation, the target of the restoration, because they were now classified as having upland heathland vegetation within the National Vegetation Classification. Considerable amounts of bracken control are grant aided as part of agri-environment schemes. These schemes should be adapted to encourage good practice, namely, intensive follow-up treatment by spraying any emerging fronds, and to encourage treatment of previously sprayed areas rather than spraying of new areas in order to protect previous investment of grant aid.

Protonemata of three mosses (Bryum rubens Mitt., Campylopus introflexus (Hedw.) Brid,. and Polytrichum formosum Hedw.) were exposed in sterile cultures to low concentrations of the bracken herbicide asulam, added to the solidified growth medium. Protonemata were either exposed for 24 hours and then transferred onto media without asulam, or exposed constantly to the asulam media. Growth was measured over a three-week period as the mean of two plug diameters, and development of leafy gametophores was noted. A 24-hour exposure period to asulam had no effect on the growth or development of the mosses at concentrations of 0.001–1 g a.i. (active ingredient) l−1. The growth and development of all three species was significantly affected by continuous exposure to asulam at concentrations of 0.01 g a.i. l−1 and above. Dose-response curves were fitted to the data and EC50 values calculated. Campylopus introflexus was the least sensitive species tested and P. formosum the most sensitive, with a 10-fold diff...

Tropical signalgrass is one of the most serious weed problems in the St. Augustinegrass sod production in Florida, and its presence increases production costs and lowers turfgrass quality. The objectives of our research were to: (1) evaluate herbicides preemergence and postemergence for control of tropical signalgrass and (2) compare control of tropical signalgrass and other problem weeds (torpedograss, blanket crabgrass, and India crabgrass) with postemergence herbicides. In preemergence herbicide field trials, only benefin + oryzalin, imazapic, imazapic + 2,4-D, and oryzalin provided ≥75% tropical signalgrass control 8 wk after application (WAA). By 11 WAA, only benefin + oryzalin and imazapic + 2,4-D provided ≥75% tropical signalgrass control. In greenhouse experiments, eight herbicide treatments were applied postemergence to tropical signalgrass seedlings at the two-, four-, six-, and eight-leaf stages. Asulam and CGA 362622 provided ≥89% tropical signalgrass control at all application timings. Imazaquin controlled tropical signalgrass ≥98% when applied before the eight-leaf stage. However, in field trials with mature tropical signalgrass (>20 cm stolons), none of the 20 herbicide treatments applied postemergence provided acceptable control.

The effects of a pesticide mixture (asulam, fluazinam, lambda-cyhalothrin, and metamitron) on aquatic ecosystems were investigated in 20 outdoor aquatic microcosms. Ten of the microcosms simulated mesotrophic aquatic ecosystems dominated by submerged macrophytes (Elodea). The others simulated eutrophic ecosystems with a high Lemna surface coverage (Lemna). This paper describes the fate of the chemicals as well as their effects on the growth of Myriophyllum spicatum and the periphytic algal community. In the Elodea-dominated microcosms significant increase in the biomass and alterations of species composition of the periphytic algae were observed, but no effect on M. spicatum growth could be recorded in response to the treatment. The opposite was found in the Lemna-dominated microcosms, in which decreased growth of M. spicatum was observed but no alterations could be found in the periphytic community. In the Elodea-dominated microcosms the species composition of the periphytic algae diverged from that of the control following treatment with 0.5% spray drift emission of the label-recommended rate (5% for lambda-cyhalothrin), while reduced growth of M. spicatum in the Lemna-dominated microcosms was recorded at 2% drift (20% for lambda-cyhalothrin). This study shows that the structure of the ecosystem influences the final effect of pesticide exposure.

Asulox is a herbicide used to control bracken. Its effects on mosses were investigated to ascertain whether exposure proved as detrimental as found in parallel studies on pteridophytes. Mature gametophytes of 18 mosses were exposed to a range of concentrations of Asulox under standard conditions and the effects on growth monitored. Plants were cut to a standard length, exposed to Asulox solution for 24 h, grown for 3 weeks and total elongation (main stem and branches) measured. EC50 values were calculated and species ranked according to sensitivity. The effects of exposure on total elongation were compared with those on main stem elongation alone. Under the conditions tested, the total elongation of all species was inhibited after exposure to Asulox. The amount of elongation observed after exposure was different for different species and inhibition of elongation occurred at different exposure concentrations. A single regression equation was not adequate to describe the dose response curves of all species tested. An ability to produce secondary branches may confer increased tolerance to Asulox exposure. It is concluded that mosses suffer detrimental effects after exposure to Asulox at concentrations similar to those that affect fern gametophytes such as bracken.

Two field experiments each conducted during a 1 year period at the Agricultural Experiment Farm, University of the Ryukyus, Japan evaluated the interval needed between sequential applications of asulam (3 kg ai ha−1) for successful control of torpedograss (Panicum repens L.). Regrowth of torpedograss from rhizomes was lowest when asulam was applied at 40-day intervals. Application at intervals of 70 days or longer completely controlled above-ground shoots but not regrowth from rhizomes. Above-ground biomass of torpedograss regrowth was 7- and 49-fold higher when asulam was applied at 70 and 100 day intervals, respectively, compared with 40-day intervals. Asulam applied three times at 40-day intervals starting 40 days after land preparation provided almost total torpedograss control 1 year after the initial application.

Bracken (Pteridium aquilinum) is a major weed of considerable economic concern in upland pastures in Bulgaria and elsewhere in Europe. Between 1993 and 1998, a field experiment was carried out to test methods for restoring productive meadows. Initially, spraying asulam (4·8 kg a.i. ha−1) was used to control the bracken on the site; this was achieved in terms of reduced frond densities and a higher level of grassland establishment. This grassland was dominated by Vicia cassubica and the perennial grasses Agrostis vulgaris, Dactylis glomerata, Festuca rubra, Holcus lanatus and Poa pratensis. After 2 years, a fertilizer addition experiment was started with four treatments (no fertilizer; addition of phosphorus; addition of nitrogen and phosphorus; addition of nitrogen, phosphorus and potassium. The phosphorus and potassium fertilizers were applied annually in the early spring at 80 kg of P ha−1 year−1 and 50 kg of K ha−1 year−1, and nitrogen was added at the start of grass growth at 60 kg of N ha−1 year−1. At the same time, a twice-yearly hay-cutting regime was implemented. Fertilizer addition increased both the quantity and the quality of the resulting grassland. The herbage dry matter was increased by at least a factor of two depending on fertilizer combination, and there was an increase in grass and legume cover and a decrease in both weed cover and bracken recovery. However, although bracken recovery was inversely related to grassland production, there was a consistent increase in bracken density across all treatments between 1997 and 1998, suggesting that increasing herbage biomass merely delays bracken recovery. The implications of these findings are discussed.

Field and glasshouse experiments were conducted from 1995 through 1996 to evaluate application timing of asulam (methyl sulfanilylcarbamate) for torpedograss (Panicum repens L.) control in relation to plant age in sugarcane. Above-ground shoots of torpedograss were completely controlled with asulam at 2–4 kg active ingredient (a.i.) ha−1 applied 60 or 80 days after planting (DAP) in artificially infested pots. But some newly developed rhizome buds survived after asulam application resulting in 1–25 and 76–100% or more regrowth in 60 and 80 DAP-applied pots, respectively. Whereas the herbicide at 2–4 kg a.i. ha−1 applied within 60 DAP completely controlled above-ground shoots, applied 80 DAP at 2 kg a.i. ha−1 it did not completely control the weed in the artificially infested field. Regrowth levels were 1–25 and 76–100% or more in 60 and 80 DAP-applied plots, respectively. Asulam at 2–3 kg a.i. ha−1 applied 20, 40, 60 or 80 DAP in a naturally infested field completely controlled above-ground shoots and regrowth levels were 76–100 or more, 51–75, 1–25 and 26–50% in these same DAP applied plots, respectively. The herbicide applied at 4 kg a.i. ha−1 caused chlorosis on younger sugarcane leaves (one-leaf stage), but when applied at 2–3 kg a.i. ha−1, no injury symptoms were shown. The herbicide at 2–4 kg a.i. ha−1 applied within 60 DAP resulted in remarkably higher yield and shoot biomass of sugarcane than that applied 80 DAP. This study suggested that asulam at 2–3 kg a.i. ha−1 should be applied 60 days after planting for the maximum control of torpedograss regrowth and better yield of sugarcane. This study also indicated that torpedograss cannot be completely controlled with a single application of asulam in a naturally infested field because of rhizome fragmentation by cross plowing and distribution of rhizomes into different soil layers that require different times to emerge. The shoots emerging after asulam application could not be controlled. Another study is required to determine the interval between sequential applications of asulam for better control of torpedograss in a naturally infested field.

Ullucus tuberosus and Amorphophallus konjac are new root crops being evaluated for commercial development in New Zealand. Eighteen herbicides were screened in glasshouse experiments for pre- or postemergence use in these crops. Methabenzthiazuron, chlorpropham, diuron and linuron were well tolerated by Ullucus when applied preemergence, while dimethanamid, oryzalin and simazine warrant further study. All the post-emergence treatments damaged Ullucus although linuron might show acceptable tolerance at a lower rate. Acetochlor, chlopropham, dimethanamid, linuron, methabenzthiazuron, oryzalin, oxadiazon, oxyfluorfen and pendimethalin were all well tolerated by Amorphophallus when applied pre-emergence, while asulam, flumetsulam and tribenuron were safely used post-emergence. Bromoxynil was also safe on Amorphophallus if applied before leaves emerged from the developing shoot.

Application of asulam herbicide by helicopter, as a primary treatment of bracken, requires appropriate buffer zones to protect non-target plants, conservation areas and water catchments from spray drift. Drift from large-scale applications of asulam were monitored at two moorland sites where helicopters were fitted with Delavan RD ‘Raindrop’ drift-reducing, hollow-cone nozzles. Drift was measured on 10 m vertical ‘strings’ and on flat cards at intervals to 200 m downwind. Potted seedlings of Rumex acetosa, as a bioassay, were exposed over similar distances. At 200 m downwind, levels of drift were close to limits of detection by high performance liquid chromatography (HPLC). With wind speeds at the legal limit for helicopter spraying, total drift fallout (integrated to 1 km downwind) accounted for 0.61% of the applied asulam. In these conditions, fallout dropped below 1% of the applied dose rate approximately 35 m downwind of the sprayed area. In general terms, beyond 15 m from the sprayed areas, drift levels from the helicopters proved similar to those reported from tractor-operated boom-sprayers. Bioassay data correlated with asulam fallout. A zero-effect level of 100 g ha−1 after 7 weeks (2.25% of the dose for bracken eradication) suggested a buffer zone of 15 m which might be doubled to 30 m to allow for inaccurate flying, late shut-off, dosage errors and species with greater sensitivity than Rumex. On the basis of this work, and also to protect private water abstractions, the Environment Agency approved a 50 m buffer zone for helicopters fitted exclusively with RD Raindrop nozzles.

Bracken is often perceived as a widespread and increasing land management problem. The pollen record of a wide range of sites in Great Britain suggests that the current abundance of bracken is less than or, at worst, equivalent to maximum historical levels. Recently gathered data also suggest that bracken cover is declining. Results of risk assessments of land use change, and experimental and modelling investigations into the effects of climate change are synthesized. This synthesis suggests that there is the potential for increased bracken dominance in northern Britain, spread into new areas at high altitudes, and possible spread into areas with reduced grazing. However, this must be set against any changes in the extent of other vegetation types at the expense of bracken. There is now a long history of bracken control, both in Great Britain and globally. Conventional methods of control (cutting, asulam application) are well understood, but many control attempts do not result in long-term success, as control is often not followed by aftercare. Bracken control is just one part of the process to ensure a sustainable use of resources and to maintain biodiversity. A coherent strategy for bracken control is put forward, a necessary part of which includes the restoration of vegetation and subsequent land management which takes into account an understanding of bracken ecology.

Fern spores were germinated, grown and exposed to different concentrations of asulam (the active ingredient of Asulox) in liquid culture. Gametophytes of Pteridium aquilinum [L. (Kuhn)] (bracken) were exposed to 100 g l − 1for 24 h at the following three stages: germination; during filamentous growth; and after transition had occurred. This treatment severely inhibited germination and killed photosynthetic gametophytes outright. Gametophytes of all species tested [ Pteridium aquilinum, Cryptogramma crispa(L.) Hook and Dryopteris filix-mas(L.) Schott] varied in their responses to lower concentrations. This variation was in terms of the response of the gametophytes and the numbers of gametophytes showing each response. Some gametophytes suffered 100% cell mortality, but in others some cells died and some survived, while the remainder of the gametophytes suffered no cell mortality. The cells affected varied from gametophyte to gametophyte at the same dose and the proportions of gametophytes showing each response changed with concentration, mortality increasing with increasing concentration. Pteridium showed lower levels of mortality at each concentration than either of the other species. The bioassay system described provides a rapid laboratory-based method to screen for Asulox susceptibility of fern gametophytes in comparison with Pteridium.

This paper describes the vegetation change in an 18-year experiment designed to test a range of control of Pteridium aquilinum (Pteridium) and heathland restoration treatments; cutting, asulam application and Calluna vulgaris seeding, in a range of combinations at Cavenham Heath in Breckland, UK between 1978 and 1996. Vegetation change was recorded in two Phases; in Phase I (1978 - 1986) species biomass was sampled and in Phase II (1986 - 1996) cover was measured. Initially, Calluna establishment was good in some treatments, especially where Calluna seed was added and Pteridium was controlled. Other plots developed either a grass- heath flora dominated by Agrostis capillaris, Deschampsia flexuosa, Dicranum scoparium, Festuca ovina and Rumex acetosella or were dominated by clonal species such as Calamagrostis epigejos or Carex arenaria. An unconstrained ordination showed significant vegeta- tion change through time and that several treatments influ- enced the vegetation, especially those involving asulam appli- cation. When variation partitioning with constrained ordina- tion was used a different explanation emerged. In Phase I the most important factors were the management treatments ap- plied, elapsed time and spatial factors, with little overlap. In Phase II, elapsed time became irrelevant because the variation time explained overlapped that which could be explained by other variables. The most important of these were manage- ment treatments, spatial effects, weather, the amount of bare ground caused by disturbance and Pteridium litter cover (an index of Pteridium recovery). The implications of these re- sults in interpreting vegetation change are discussed.

In glasshouse experiments,Panicum repensrhizomes with more than two nodes emerged from soil depths of 1 to 20 cm. Emergence from one-node rhizomes was greatly reduced at depths more than 5 cm. In contrast, culm emergence from ginger like rhizomes decreased when burial depth (BD) was greater than 20 to 30 cm.P. repensemerged from deeper soil levels with an increasing number of nodes per cutting. Culms emerged from 36% of total underground regenerative organs. About 75 and 95% of the emerged culms were recorded 30 and 60 d after burial, respectively, and 91% emergence was recorded from 20-cm BD. In field studies, only 9% of nodes produced culms following cross-plowing. About 61 and 67% of the emerged culms were recorded 50 and 60 d after land preparation, respectively. Results indicate that mechanical and chemical control methods could be most effective forP. repenswhen applied approximately 50 d after land preparation. Burying deeper than 30 cm by deep plowing and reducing rhizome length by cross-plowing might effectively reduce emergence ofP. repens.

1. The effects of six bracken control treatments applied in combination with a Calluna* seeding treatment on the rhizome system of bracken Pteridium aquilinum at Cavenham Heath in Breckland was assessed after 18 years. Bracken control included cutting once and twice yearly between 1978 and 1996; spraying the herbicide asulam at the recommended rate (4·4 kg a.i. ha−1) in two treatments (1978 and 1978 plus 1979), each followed by repeat doses in 1984 and 1990, and spraying asulam followed by cutting once yearly. After 6 years the experiment was split and bracken control was continued/reapplied on half the plots and stopped on the remainder. The effects of treatment on the numbers of active and dormant buds and the length and biomass on both frond-bearing and storage rhizomes were measured. 2. When applied continuously over the 18 years, all treatments reduced all rhizome measures, but treatments that included cutting were more effective than ones that just used asulam. The best treatment after 10–12 years was cutting twice yearly, but after 18 years this treatment had apparently reached an equilibrium and the cutting-once-yearly treatment was superior. No treatment eradicated the bracken in 18 years of continuous treatment. 3. When bracken control treatments were stopped after 6 years rhizome recovery started within 4 years and there was significant recovery thereafter. After 12 years the least effective treatment, cut once yearly, although still showing a significant reduction in rhizome biomass, had recovered to 88% of the untreated plots. The most effective treatment was cutting twice yearly for 6 years, where most measures of rhizome performance remained at approximately 50% of untreated plots 12 years after cutting stopped. 4. Regression analysis was used to investigate the relationship between frond production and rhizome characteristics. Rhizome biomass, especially of the storage rhizome component, was consistently the most important variable; frond bud numbers were less important. 5. Simple models, developed making assumptions that the response of the rhizome to treatment is linear through time, have been shown to be invalid over the longer time period. This is because the impacts of the treatments reduce through time. 6. These results are discussed in relation to long-term bracken control and the assessment of bracken stocks. If bracken is to be suppressed on a long-term basis a continuous control strategy is needed. It is unlikely that complete eradication will be possible with current control technology. The long time scale found for the total recovery of the bracken from only 6 years of treatment (>12 years) means that the large areas of bracken that have been treated in the past will take some time to recover to pretreatment levels. This recovery is an unknown factor in bracken stock assessments.

Control of Rumex species in phalaris (Phalaris aquatica L.) by four herbicides and tolerance of phalaris seed crops to a range of herbicides was investigated in two trials. Dicamba at 400 g/ha gave 100% control of Rumex species in both years (0 and 1 Rumex seed/40g phalaris seed). Thifensulfuron at 15 g/ha gave 100% and 99.7 control (0 and 15 seeds/ 40g). These treatments were more effective than asulam or a 2,4-D + dicamba mixture. Phalaris seed yields had good tolerance to mecoprop and dichlorprop mixtures, tribenuron-methyl, TCA + 2,2-DPA, prodiamine, and diflufenican + bromoxynil. Fenoxyprop-P-ethyl is not recommended for phalaris seed crops.

The vegetation of 117 bracken-dominated sites that had been sprayed with asulam from the air over a wide range of dates was recorded. There is a high variability in initial efficacy and sites displayed considerable differences in regeneration in the years following treatment. Sites treated more than 10 years previously all showed good control of bracken. The absence of sites where bracken has regenerated completely was attributed to either respraying at a later date or the poor records kept of previous unsuccessful control measures. There was also a high degree of variation in the amount and type of herbaceous vegetation present below untreated bracken. The data presented suggest that aerial spraying of bracken with asulam can be a long-term and cost-effective control method. However, in the light of experimental results from other studies, the success of an individual operation is critically dependent on the initial efficacy of treatment, the initial floristic composition (if any) and suitable follow-up management.

Six herbicides were evaluated for their effects on Pythium root rot and growth of sugarcane in greenhouse experiments and on in vitro mycelial growth rate of Pythium arrhenomanes. Pendimethalin and atrazine were most inhibitory to mycelial growth, but neither reduced root rot severity. Asulam, atrazine, and metribuzin were not phytotoxic to sugarcane and did not affect root rot symptom severity in clay loam or silt loam field soils. Atrazine and metribuzin increased shoot number, and atrazine increased total shoot weight for treated plants in silt loam soil. Glyphosate, pendimethalin, and terbacil were phytotoxic to sugarcane. These herbicides increased root rot severity, but the extent to which growth reductions resulted from increased disease severity or from direct herbicide injury was not clear. Adverse effects on plant growth and root rot severity were greater in clay loam than in silt loam soil. The results suggest that sugarcane injury from some herbicides is compounded by increased severity of root rot.

Root-attaching parasitic flowering broomrapes (Orobanche spp.) are major constraints to vegetable, legume and sunflower production around the Mediterranean and elsewhere, with banned methyl-bromide fumigation or land abandonment of these affected crops as the major “solutions” to the problem. We report the specific generation of transgenic asulam-resistant potatoes as a way to eradicate this pest. The target-site resistance in the crop allows the herbicide to be translocated from treated leaves to the parasite via crop roots. This inhibitor of dihydropteroate synthase lethally then prevents folic acid biosynthesis in the parasite. Additionally, we demonstrate that asulam can be used directly in selecting resistant transformants, without the need for another selectable marker.

Torpedograss (Panicum repens L.) is a serious rhizomatous perennial weed in sugarcane (Saccharum offacinarum L.) in Taiwan, Hawaii and Okinawa. Two experiments were conducted to investigate torpedo-grass control and sugarcane injury using 2, 3 and 4kg ai/ha of asulam (methyl sulfanilyl carbamate) based on the time of herbicide application in the early growth stage of sugarcane. The asulam formulations used were SL (soluble concentrate, 37%) and WG (water soluble granule, 80%). Each formulation was applied at 20 days after planting (DAP) in the first experiment, and at 40DAP in the other experiment. Asulam SL and WG at 2 to 4kg ai/ha gave 100% control of torpedograss when applied either at 20 or 40DAP. Asulam applied at 20 and 40DAP required about 28 and 35 days after treatment, respectively to control torpedograss completely. Higher growth, yield and yield parameters of sugarcane were obtained by the 20DAP application of both formulations at 2kg ai/ha than those at higher rates. The formulations at 4kg ai/ha applied at 20DAP had severe injury effects on growth, yield and yield parameters of sugarcane, while 2, 3 and 4kg ai/ha of the formulations applied at 40DAP caused no negative impact on sugarcane growth, yield or yield parameters. Yield of sugarcane was significantly increased by all examined rates of the two asulam formulations applied at 40DAP in comparison with those of untreated weedy crop cultivation. The results of these experiments suggest that both asulam formulations (SL and WG) at 2kg ai/ha would successfully control torpedograss in sugarcane by post emergence application within 20-40 days of planting.

A mixture of seashore paspalum (Paspalum vaginatum Swartz) with bermudagrass (Cynodon spp.) results in an overall poor quality turf on golf course fairways. A field experiment was conducted at two locations during 1997 in Hawaii to determine if herbicides would control paspalum encroachment without causing undesirable injury to the bermudagrass. Three applications of Asulox (asulam) applied alone at a total rate of 4.4 kg/ha (4.0 lb/A) or with Image (imazaquin) suppressed paspalum ≥97% by 8 weeks after the initial treatment and ≥83% by 10 weeks. The suppression from three applications of Trimec Plus (MSMA + 2,4-D + mecoprop + dicamba) at a total rate of 11.1 kg/ha (9.6 lb/A) was ≥63% at 8 weeks and ≥70% by 10 weeks. Paspalum suppression from an initial application with Trimec Plus followed by two Asulox treatments was not advantageous, compared with three Asulox treatments. Three applications of Trimec Plus suppressed at least 70% paspalum by 10 weeks. The suppression was poor when treated with Ally (metsulfuron) and sequential applications with Surflan (oryzalin) and MSMA. Tifway bermudagrass (C. transvaalensis x C. dactylon) was severely injured when treated with all herbicides except Ally and Surflan plus MSMA. Maximum injury ranged from 40% when treated sequentially with Trimec Plus and Asulox, to 50% when treated with Asulox, 57% when treated with Asulox plus Image, and 91% when treated with Trimec Plus. By 10 weeks, bermudagrass had started to recover but the overall injury ranged from 28% to 40%.

Heathlands tend to occur on low fertility soils, but where heathland has been invaded by bracken Pteridium soil nutrient concentrations may be increased. In order to reestablish Calluna-dominated heathland these elevated soil nutrient concentrations may have to be reduced. This paper describes an attempt to re-create an area of Calluna-dominated heath on land which had been invaded by bracken. Several management techniques were implemented in a hierarchical manner to control a dense bracken stand, including: litter stripping, ploughing and traditional bracken control methods such as cutting and herbicide treatment. Finally a heathland propagule source, which was rich in Calluna seeds, was added. The effects of these treatments on both nutrient budgets and soil chemical properties were also investigated. Litter stripping removed a large amount of nutrients, ranging between 19 and 98 years' worth of rainfall inputs depending on the element. Ploughing caused an initial reduction in frond density and biomass but effects were not significant thereafter. Cutting twice yearly was the most effective treatment in reducing frond biomass. The establishment of Calluna seedlings was directly related to the success of the bracken control treatments.

Summary A nationwide bracken control experiment provided data over a three-year period for testing the accuracy of a bracken growth model (BRACON). Objective assessments of model validity identified the model as a reasonably accurate predictor of bracken stand dynamics given the range of environmental conditions currently prevailing in Great Britain, in relation to (1) cutting regimes and (2) spraying asulam. Ranking of treatment efficacy at individual sites was closely reflected in model predictions. Predicted response of the rhizome system to cutting treatments underestimated bracken resilience. Failure to consider the consequences of frond regrowth in the latter portion of the growing season as a means to offsetting energy loss was identified as a potential explanation for this discrepancy. The role of the model as a practical management tool is discussed with particular reference to relating model predictions, based upon generalised environmental data (40 km plusmn; 40 km grid cells), to bracken management at individual sites.

Summary Bracken control field experiments were conducted at six locations across Great Britain. The effects of various cutting and herbicide management regimes upon the seasonal dynamics of bracken fronds and rhizomes were examined over a three year period. This enabled a national overview towards bracken control to be constructed. Initially, spraying with asulam was the most effective treatment in reducing frond biomass and density but was least effective in reducing rhizome biomass. Differential reductions in rhizome biomass were observed in relation to cutting frequency, with cutting twice yearly giving superior control. The national trends confirmed a number of previous observations from independent single-site studies; however, others were contradicted. Comparable management options were ranked consistently between the current and former investigation, however, the initial importance of differences in cutting frequencies did not agree between studies. This multiple-site study improves understanding of the consequences of a national bracken control programme by reducing the influence of confounding site-specific factors, and recommendations for the most appropriate bracken control techniques are made. The extent to which individual sites reflect a national trend in response to bracken control is considered and sites are compared. The hierarchy of treatments identified at the national scale was found to apply generally within individual sites. However, several responses which proved significant at the countrywide level were not so clearly defined at the site scale. Cutting once yearly was the only management regime which appeared to give different bracken control between sites. All other treatments gave similar responses between sites. This result was found in the Scottish Borders, during the second year of control, when frond biomass and density (relative to untreated plots) were greater than that recorded at other sites. This contrast was not found in subsequent monitoring. In terms of rhizome biomass depletion, poorer control was achieved following cutting once yearly at the northern sites (Mull, Scottish Borders, Lake District) compared with the southern sites (Clwyd, Breckland, Devon). The implications of experimental results are discussed in relation to increased cost effectiveness of national bracken control programmes.

A range of moorland sites in the North York Moors, North Yorkshire, UK, where bracken control with the herbicide asulam has been carried out, has been re-surveyed. The trajectory of vegetation change at each site has been analysed using a range of techniques. Vegetation change after spraying appears to depend on three things—the species present at the time of control, the initial effectiveness of treatment and the amount of subsequent disturbance (mainly by sheep). Where grazing pressure was low, there was little invasion or spread of plants, except on sites with an initial moderate cover of Vaccinium myrtillus . Where high sheep activity disturbed the litter layer, invasion by the moss Campylopus introflexus characteristically occurred, followed by an increase in dominance by grasses, especially Deschampsia flexuosa . Where grazing pressure was high enough, it appeared that bracken regeneration was slowed, otherwise the bracken canopy and the stand recovered. However, in the timescale of the study, sufficient variety and cover of other species remained after the canopy regenerated to prevent the complete progression to vegetation characteristic of untreated areas.

Summary The effect of non-ionic nonylphenol (NP) surfactants containing 4–14 ethylene oxide (EO) molecules on the distribution of asulam and diflufenican was investigated in Pteridium aquilinum L. Kuhn and Avena fatua L. The distribution of the herbicides was dependent on the EO content and concentration of surfactant and differed between plant species and herbicide. The surface properties of contact angle, droplet diameter and surface tension were examined. For solutions of asulam, the greatest reductions in contact angle, surface tension and greatest droplet diameter were obtained with surfactants of EO 6.5–10 (at 0.001–0.1%). For solutions of diflufenican, these responses were greatest when applied with surfactant of EO 4. Surfactants of EO 6.5–10 increased the uptake and translocation of [14C]asulam in P. aquilinum, particularly at surfactant concentrations of 0.01 % and 0.1 %. All surfactants increased uptake of [14C]asulam in A. fatua with no significant effects of surfactant EO number or concentration. For both species, there was a positive correlation between the optimum surface characteristics of the herbicide droplets and the uptake of asulam. With diflufenican, greatest uptake and translocation by mature frond tissue of P. aquilinum occurred at the highest concentration of surfactant EO 4; in A. fatua, however, uptake and translocation were not significantly affected by any of the surfactants.

Asulam is often applied from the air to control bracken. This herbicide affects other ferns and spray drift could affect their survival. This paper discusses the use of bioassays to assess drift (a) spatially around a single bracken patch, (b) downwind from sprayed areas, and (c) spatially in undulating terrain and with different vegetation cover types. The aims were to develop policies to protect sensitive habitats. It is suggested that “no-spray” buffer zones in excess of 160–180 m are needed to minimise risk. Protection of rare ferns from overstorey vegetation or from steep slopes did not occur. Although less drift was found upwind there was significant damage at the end of the helicopter runs because of errors in switching the sprayer on and off.

Field studies were conducted over 3 yr to evaluate rhizome johnsongrass control with asulam applied POST at 3.7 kg ai/ha 3 d before fertilization (DBF) or 0, 3, 7, 10, or 14 d after fertilization (DAF). Liquid fertilizer (18-6-12) was applied with injector knives at 0, 112, or 224 kg N/ha 5 cm on each side of a 60-cm line of rhizome johnsongrass present on 1.8-m-wide conventional sugarcane beds. Johnsongrass response to timing of asulam application after fertilization varied among years but was not affected by fertilizer rate. Johnsongrass control with asulam applied 3 DBF was greater than applications made 0, 3, or 7 DAF. With one exception, differences in johnsongrass control following fertilization and asulam application times were also reflected in the biomass of treated johnsongrass and its regrowth harvested 6 and 10 wk after asulam application, respectively. Reduced johnsongrass control associated with asulam application following fertilization was related to stress from root/rhizome injury during fertilizer placement rather than the quantity of fertilizer applied.

A rainfall simulator was used to deliver the equivalent of 1.3 cm of water in 0.25 h at 0, 3, 6, 12, 24, and 48 h after POST applications of asulam to johnsongrass in greenhouse and field studies. Johnsongrass control responses were similar when asulam was applied with either a crop oil concentrate or a commercially blended organosilicone/crop oil concentrate premix. Rainfall 24 h after asulam application reduced johnsongrass control in greenhouse studies. Maximum visual johnsongrass control of 80, 69, and 69% was obtained in field studies when rainfall occurred 20, 14, and 8 h after asulam application, respectively. Based on reductions in johnsongrass dry weight, rainfree periods needed to insure maximum performance with asulam in field studies ranged from 3 to 16 h. Variation in critical rainfree periods was related to plant growth stage when asulam was applied and environmental conditions and is indicative of the inconsistency in johnsongrass control commonly observed with asulam. Nomenclature: Asulam, methyl[(4-aminophenyl)sulfonyl] carbamate; johnsongrass, Sorghum halepense (L.) Pers. # 3 SORHA.

The responses of seed‐derived progenies of an MCPA‐resistant (R) and an MCPA‐susceptible (S) population of Ranunculus acris to a range of doses of MCPA, 2,4‐D, MCPB, chlorsulfuron, and thifensulfuron were compared under glasshouse conditions. In a second experiment, also under glasshouse conditions, the responses of R and S to the usual field doses of tribenuronmethyl, bentazone, glyphosate, clopyralid, and asulam were compared. R was cross‐resistant to both 2,4‐D and MCPB. There was temporary cross‐resistance to chlorsulfuron and thifensulfuron manifest in slower development of apical mortality in R plants but all R and S plants ultimately died at the usual field dose rates of these two herbicides. There was weak evidence of cross‐resistance to bentazone but no evidence of resistance to either tribenuron‐methyl or glyphosate since both resulted in 100% mortality of R and S at usual field dose rates. Clopyralid and asulam had no effect on either R or S. The results indicate that neither 2,4‐D nor...

Summary This paper examines the initial effects of bracken control on frond numbers and biomass, and the biomass, carbohydrate reserves and bud densities of bracken stands cut once per year, twice per year, subject to a single application of asulam or left untreated. The seasonal dynamics of these parameters are displayed; carbohydrate and biomass are both removed from the rhizome system to produce frond tissue, and are replenished at the end of the growing season. Asulam application reduced densities of both active and dormant buds, and both frond biomass and density. It did not significantly reduce rhizome biomass or carbohydrate reserves in the two years after treatment. Cutting, either once or twice per year reduced both rhizome biomass and rhizome carbohydrate reserves, as well as bud densities, though the latter were reduced in proportion to biomass. Cutting twice a year reduced the production of fronds, both in numbers and biomass. The collected data were used to evaluate a model of bracken growth, and subsequently to improve estimates of some of the model parameters. The model simulations of control treatments were compared to field data. The effects of cutting once per year and spraying with asulam were predicted accurately, but the bracken stand was more resilient to cutting twice per year than would be expected from model predictions. The combination of cutting and spraying is discussed as a potential tool in land management and the deficiencies of the model are discussed in relation to the need for future research into the biology of bracken.