Organophosphate degradation by insecticide-resistant and susceptible populations of mosquitofish (Gambusia affinis)

Phosphorothionate and phosphate degradation was investigated as a factor which could influence the tolerance of organochlorine compound-resistant and susceptible mosquitofish (Gambusia affinis) to parathion and methyl parathion. The greater toxicity of methyl parathion than parathion can be attributed in part to a higher rate of degradation of methyl paraoxon than paraoxon (7-fold), but not to any difference in phosphorothionate dearylation. Resistant fish possess higher levels of microsomal mixed-function oxidases which can degrade methyl parathion (1.3-fold); these higher levels could contribute to the increased methyl parathion tolerance by this population over the susceptible population. Environmentally induced tolerance to parathion in the resistant population may be the result of increased levels of parathion degradation by induced mixed-function oxidases which can dearylate parathion. The increased tolerance of either insecticide by the resistant population is not caused by degradation of the phosphates by phosphotriesterases.     

Control of Cirsium arvense (L) Scop, by herbicides and mowing

The efficacy of mowing and of herbicides (applied by spot spraying or boom spraying) for the selective control of Cirsium arvense (L) Scop, in Victorian pastures was investigated. The pastures were based on Trifolium repens L. and Lolium perenne L. A general decline in the number of thistle shoots in untreated plots at three out of five sites was recorded.‘Tordon 50-d' (5% a.i. picloram and 20% a.i. 2,4-D as triisopropanolamine salts), MCPB, 2,4-DB and mowing resulted in suppression, but not eradication, during the experimental period. MCPB and 2,4-DB are the most suitable herbicides for selective control. The use of‘Tordon 50-d' is restricted by its effect on clovers, soil persistence and cost. Variable growth of C. arvense, associated with variable summer rainfall in Victoria, increases the difficulty in controlling this weed and necessitates a persistent long term approach.     

The effect of temperature on glutathione S-transferase activity and glutathione content in Alopecurus myosuroides (black grass) biotypes susceptible and resistant to herbicides

Herbicide‐resistant populations of Alopecurus myosuroides (black grass) have become widespread throughout the UK since the early 1980s. Previous observations in this laboratory have demonstrated that natural climatic fluctuations caused increases in endogenous glutathione S‐transferase (GST) enzyme activity in A. myosuroides plants as they mature, which is thought to be linked to herbicide resistance in this species. The present study has investigated the effects of plant growth at 10°C and 25°C, and reports GST specific activity and glutathione (GSH) pool size in resistant and susceptible A. myosuroides biotypes. Findings demonstrate differences in GST activity between resistant and susceptible populations, which are transient at lower growth temperatures. The GSH pool size was elevated at lower growth temperature in both biotypes. We speculate that these endogenous responses are part of a natural mechanism of acclimation to environmental change in this species and suggest that resistant plants are more able to adapt to environmental stress, as indicated in this instance by temperature change. These observations imply that the control of resistant A. myosuroides by graminicides may be more effective when applied at lower temperatures and at earlier growth stages.     

Compatibility of the commercial biological control agents Trichoderma asperellum (ICC 012) and Trichoderma gamsii (ICC 080) with selected herbicides

Journal of Plant Diseases and Protection - The in vitro effects on mycelial growth of the antagonistic fungi Trichoderma asperellum (ICC 012) and Trichoderma gamsii (ICC 080) were studied based on...     

Transformation of the herbicides propanil and chlorpropham by micro-algae

Two species of green algae and four of blue-green algae hydrolysed the acylanilide herbicide propanil to the aniline derivative, 3,4-dichloroaniline. Of the cultures tested, only the blue-green alga Anacystis nidulans was shown to be capable of converting the phenylcarbamate herbicides propham and chlorpropham to the corresponding anilines. The green alga Ulothrix fimbriata was apparently unable to hydrolyse propanil or chlorpropham.     

Purification and characterisation of a family of glutathione transferases with roles in herbicide detoxification in soybean (Glycine max L.); selective enhancement by herbicides and herbicide safeners

Glutathione transferases in soybean (GmGSTs) involved in herbicide detoxification in cell suspension cultures were purified by S-hexylglutathione affinity chromatography and resolved by a combination of HPLC and SDS-PAGE into 11 polypeptides. Analysis by Western blotting using antisera raised to three previously characterised tau (GmGSTU) class subunits demonstrated that five polypeptides were related to GmGSTU1, three to GmGSTU2, and one to Gm GSTU3. Plants contained a simpler profile of polypeptides, with a single GmGSTU2-like polypeptide predominating. With respect to herbicide detoxification, two GmGSTU2-related polypeptides dominated the activity toward the chloroacetanilide acetochlor, while an unclassified subunit was uniquely associated with the detoxification of diphenyl ethers (acifluorfen, fomesafen). The inducibility of the different GST subunits was determined in soybean plants exposed to photobleaching diphenyl ethers and the safeners naphthalic anhydride and dichlormid. GmGSTU3, a GmGSTU1-like polypeptide, and thiol (homoglutathione) content were induced by all chemical treatments, while two uncharacterised subunits were only induced in plants showing photobleaching.     

Leaf spot of St Augustine grass (Stenotaphrum secundatum) caused by Cochliobolus bicolor

The Bipolaris state of Cochliobolus bicolor was shown by isolation and inoculation to be the cause of a leaf spot of St Augustine grass in Viçosa, Minas Gerais, Brazil. Leaf spotting was much more frequent when the grass was in a mixed stand with Kikuyu grass (Pennisetum clandestinum).     

The influence of herbicides on the viability of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae)

Entomopathogenic nematodes (EPNs) are agents that can be used for the biological control of pests associated with pesticides in a tank mix. Compatibility studies need to be conducted to analyse which products are compatible with EPNs. The survival of infective juveniles (IJs) of four species of EPNs (Steinernema, Heterorhabditis) was determined after exposure to eight chemical herbicides. The effect of direct IJs exposure to herbicides for 1, 4 and 24 h was tested in a Petri dish at 15, 20 and 25 °C. The study showed that Steinernema kraussei was the most tolerant among the tested EPN species, while S. carpocapsae was the most sensitive to all tested herbicides. The lowest mortality of IJs was at 15 °C (19%). Our investigation showed, overall, the herbicides negatively affected EPN survival. The results confirmed that the compatibility is a species-specific characteristic, influenced by the temperature and time of exposure. Application of two different control ingredients (insecticide and herbicide) at the same time would reduce cost and time consumption in pest/weed control.     

Characterisation of target-site resistance to ACCase-inhibiting herbicides in the weed Alopecurus myosuroides (black-grass)

Resistance to aryloxyphenoxypropionate (AOPP), cyclohexanedione (CHD) and phenylurea herbicides was determined in UK populations of Alopecurus myosuroides Huds. Two populations (Oxford AA1, Notts. A1) were highly resistant (Resistance indices 13-->1000) to the AOPP and CHD herbicides fenoxaprop, diclofop, fluazifop-P and sethoxydim, but only marginally resistant to the phenylurea, chlorotoluron. Analyses of acetyl coenzyme A carboxylase (ACCase) activity showed that an insensitive ACCase conferred resistance to all the AOPP/CHD herbicides investigated. Another population, Oxford S1, showed no resistance to sethoxydim at the population level, but contained a small proportion of plants (<10%) with an insensitive ACCase. Genetic studies on the Notts A1 and Oxford S1 populations demonstrated that target site resistance conferred by an insensitive ACCase is monogenic, nuclearly inherited with the resistant allele showing complete dominance. Investigations of the molecular basis of resistance in the Notts A1 population showed that sethoxydim resistance in A myosuroides was associated with the substitution of an isoleucine in susceptible with a leucine in resistant plants, which has also been found in three other resistant grass-weed species (Setaria viridis (L) Beauv, Avena fatua L, Lolium rigidum Gaud).     

Seed germination ecology of creeping mannagrass (Glyceria acutiflora) and response to POST herbicides

Creeping mannagrass is a perennial grass weed widely distributed in China and is becoming increasingly problematic in nurseries and landscapes in some regions. Understanding the germination ecology and response to commonly available POST herbicides of this weed is critical to determining its adaptive capabilities and potential for infestation, and assist in the development of effective control strategies. In the light/dark regime, creeping mannagrass germinated over a wide range of temperatures (15/5 to 30/20°C), with maximum germination at 20/10°C (95%). No seed germinated at 35/25 or 10/0°C. The time required for 50% of maximum germination increased as temperature decreased. Compared with the light/dark conditions, germination was slightly stimulated when seeds were placed in the dark. Creeping mannagrass is moderately tolerant to osmotic and salt stress, which had 53 and 50% germination rates at ?0.6 mPa osmotic potential and 200 mM NaCl concentration, respectively. Seedling emergence of the seeds buried at a depth of 0.5 cm (86%) was higher than those sowing on the soil surface (17%), but declined with burial depth increasing. There were no differences in the emergence rates from a burial depth 0.5–2 cm. Few seeds (4%) could emerge when seeds were sowed at a depth of 8 cm. POST application of haloxyfop‐R‐methyl, quizalofop‐p‐ethyl, sethoxydim, and pinoxaden provides 100% control of creeping mannagrass at the three‐leaf to five‐leaf stages. To achieve 80% control with clodinafop‐propargyl, mesosulfuron‐methyl, and fenoxaprop‐p‐ethyl, herbicides had to be applied at the three‐leaf stage.     

Influence of nitrogen fertilization and isoxaflutole on the nodulation of chickpea (Cicer arietinum)

The effects of soil nitrate and the herbicide, isoxaflutole, on chickpea nodulation were examined in a glasshouse experiment. The treatments consisted of one isoxaflutole‐tolerant and one isoxaflutole‐sensitive chickpea cultivar, five nitrate concentrations (0, 0.75, 1.5, 3.0, and 6.0 mmol L^?1), and three herbicide rates (0, 75 [the recommended rate], and 300 g ha^?1). The sensitive cultivar was more susceptible to isoxaflutole damage with an increasing herbicide rate and nitrate concentration, compared with the tolerant cultivar. Isoxaflutole at the recommended rate reduced the nodule dry weight of the sensitive cultivar by 51% and by 33% in the tolerant cultivar. The nodule dry weight of the sensitive cultivar was reduced by 28%, 40%, 64%, and 76% with the addition of the 0.75, 1.5, 3.0, and 6.0 mmol L^?1 nitrate concentrations, respectively. In comparison, the nodule dry weight of the tolerant cultivar was reduced by 50% and 79% at the 3.0 and 6.0 mmol L^?1 nitrate concentrations, respectively. In addition, the level of damage from increasing rates of isoxaflutole increased with the highest nitrate concentrations of 3.0 and 6.0 mmol L^?1, regardless of the cultivar. Isoxaflutole at the recommended application rate had a detrimental effect on the nodulation of both chickpea cultivars, but the isoxaflutole‐tolerant cultivar suffered less injury than the sensitive one in relation to some growth parameters. The damage to chickpea from the recommended rate of isoxaflutole also increased with soils of higher nitrate content.     

Action of two herbicides on the microbial activity of soil cultivated with common bean (Phaseolus vulgaris) in conventional-till and no-till systems

The effects of application of the herbicides fluazifop‐p‐butyl and fomesafen and the commercial mixture of these herbicides on the microbial activity of a soil, cultivated with common bean under no‐till (NTS) and conventional‐till (CTS) systems, were evaluated. Microbial respiration was monitored for 63 days after application (DAA) of the herbicides, and the following evaluated at 12 and 51 DAA: microbial biomass carbon (MBC), microbial quotient (qMIC), metabolic quotient (qCO₂), percentage of bean root colonisation by mycorrhizal fungi and grain yield at the end of the cycle. A greater microbial respiratory rate was observed under NTS, with fluazifop‐p‐butyl providing the lowest respiration. At 12 DAA, MBC and qMIC were most affected negatively by fomesafen and by the commercial mixture of the two herbicides. Mycorrhizal colonisation was affected by the herbicides only at 12 DAA under CTS; however, in both periods, the highest value was found under NTS. All the herbicides caused a decrease in the MBC and qMIC values at 51 DAA; the qCO₂, which is related to the soil system stability, indicated a greater NTS balance over CTS. The herbicide fomesafen induced lower stability in the system. Lower grain yield was obtained without weed control (no herbicides) and with fomesafen‐only treatments, which may be attributed to the high weed infestation in the experimental area.     

Analysis of nematodes and soil-borne fungi fromAmmophila arenaria (Marram grass) in Dutch coastal foredunes by multivariate techniques

A survey was carried out at nine locations in the Dutch coastal foredunes to identify the species of soil borne fungi and nematodes associated withAmmophila arenaria (Marram grass).Ammophila arenaria is a sand binding grass that is very important for the stabilization of coastal foredunes. Degeneration of the plants occurs at stabilized sites and is supposed to be caused by a combination of soil-borne fungi and nematodes. Canonical correspondence analysis (CCA) and two-way indicator species analysis (TWINSPAN) were used to examine which fungal and nematode species usually coexist in the rhizosphere of vigorous and early declining stands ofA. arenaria. In total, 47 species of fungi and 10 genera of plant-parasitic nematodes were found. According to CCA, the community of soil organisms of stands that were more than 10 years old was significantly different from recently established stands of 3 years old. Also, the community of soil organisms isolated from calcareous locations differed significantly from that of lime-poor locations. No relationship between the vigour of the plants (vigorous vs. early declining) and the soil borne species composition was found, although in roots of vigorous stands, the number of nematodes was higher than that of early declining stands. A relatively large group of soil organisms occurred generally. This group possibly contains an ubiquitous pathocomplex that cause the growth reducing effects of biotic origin which generally occur inA. arenaria. Analysis of this group of nematodes and fungi by TWINSPAN resulted in 9 different combinations of concurring soil organisms of which 5 combinations were present at all investigated locations. Two of the latter combinations contained both nematodes and fungi. The first contained three endoparasitic nematodes (Meloidogyne maritima, Heterodera spp. andPratylenchus sp.) that concurred with the fungusMucor hiemalis. The second group containedHeterodera spp.,Telotylenchus ventralis, Filenchus sp. together with the potentially plant-pathogenic fungiMicrodochium bolleyi and Fusarium culmorum, as well as the fungiMortierella sp. andTrichoderma harzianum, all in relatively high numbers.It is concluded that both CCA and TWINSPAN are valuable exploratory techniques, especially when used in combination, to detect possible combinations of soil organisms which may be involved in the degeneration ofA. arenaria. Further identifications of harmful organisms should be obtained from experiments.     

Some data concerning the presence and behaviour of springtails (Collembola) on grass and white clover

No proof was found that Collembola prefer white clover to grass in sandy soils of leys and grasslands. The same springtail species can be found on both. However, in greenhouses they definitely preferred the white clover. Here,Folsomia quadrioculata especially, and during the summer monthsSminthurinus trinotatus, were found. In winter,Onychiurus bicampatus or a related species was also identified.Folsomia quadrioculata is able to feed on white clover roots. In doing so, invasion spots are prepared for weakly parasitic soil fungi. Addition of these fungi to the soil, however, did not result in an infestation of the roots followed by death and disappearance of the white clover, forFolsomia then preferred to feed on the fungi rather than on the roots.     

PCR-based detection of resistance to acetyl-CoA carboxylase-inhibiting herbicides in black-grass (Alopecurus myosuroides Huds) and ryegrass (Lolium rigidum gaud)

A simple method based upon allele-specific PCR was developed to detect an isoleucine-leucine substitution in the gene encoding chloroplastic acetyl-coenzyme A carboxylase (ACCase) in two gramineous weeds: Lolium rigidum Gaud and Alopecurus myosuroides Huds. Analysis of 1800 A myosuroides and 750 L rigidum seedlings showed that the presence of ACCase leucine allele(s) conferred cross-resistance to the cyclohexanedione herbicide cycloxydim and to the aryloxyphenoxypropionate herbicides fenoxaprop-P-ethyl and diclofop-methyl. Seedlings containing ACCase leucine allele(s) could be either sensitive or resistant to the aryloxyphenoxypropionate herbicides haloxyfop-P-methyl and clodinafop-propargyl. Successful detection of resistant plants in a field population of A myosuroides was achieved using this PCR assay. Using it with basic molecular biology laboratory equipment, the presence of resistant leucine ACCase allele(s) can be detected within one working day.     

Regenerative capacity and response to pre‐emergent herbicides by stolon fragments of triquetrous murdannia (Murdannia triquetra) in rice

Triquetrous murdannia is an annual stoloniferous weed commonly found in wheat‐rice rotation fields in China. Disturbance after wheat harvesting can fragment stolons of triquetrous murdannia, and the regeneration of these fragments may contribute to the spread of this weed. In this study, the regenerate capacity and response to pre‐emergence (PRE) herbicides of stolon fragment of triquetrous murdannia were evaluated in a screenhouse. The experiment consisted of two types of single node fragments (2‐cm stolon node and five‐leaf stolon tips) placed under different floating, flooding and burial depth conditions. Results indicated that floating depth did not influence the survival of the two types of fragments but significantly decreased their growth (stolon length, number of branches, and biomass). The stolon nodes were more sensitive to flooding than stolon tips; no stolon node survived at a flooding depth of 6 cm. The highest survival was observed for fragments placed on the soil surface, and no fragments buried to a depth of 2 cm survived. PRE application of benzobicyclon, butachlor, metazosulfuron, and triafamone significantly decreased the branching and biomass of the stolon nodes; however, only triafamone and metazosulfuron significantly inhibited the regeneration of the stolon tips. These results suggest that stolon fragments with one node are likely to promote vegetative reproduction in triquetrous murdannia, and thus, disturbance may contribute to the spread of this weed. Tillage to bury fragments below their maximum regeneration depth and application of an effective PRE herbicide could serve as important tools for managing triquetrous murdannia.     

Effects of nitrogen fertilization and cutting frequency on the competitive ability and the regrowth capacity of Rumex obtusifolius L. in several grass swards

The broad-leaved dock (Rumex obtusifolius L.) is widely distributed, and is perceived as a major weed problem in intensively managed permanent grassland. The effects of nitrogen fertilization (120; 240 or 480 kg N ha^?1), cutting frequency (every 4 or 6 weeks) and competing grasses on development, dry matter production and stem growth of Rumex were studied under field conditions. Young plants of Rumex were planted into established pure swards of Lolium multiflorum Lam., Lolium perenne L., Alopecurus pratensis L. and Poa pratensis L. In all treatments, only Lolium multiflorum hindered the growth of R. obtusifolius substantially. Cutting intervals of 6 weeks were more favourable to Rumex than were 4-week intervals. Its proportion of herbage yield increased from 2% at 120 kg N ha^?1, taken as an average of the three grass swards (Lolium multiflorum not included), to 18% at 480 kg N ha^?1. The reproductive capacity of Rumex was greatly influenced by the competing grass species: in the P. pratensis sward, Rumex developed up to 12.3 stems with inflorescences per plant per year, but only 0–9 stems developed in the L. multiflorum plots. The regrowth potential of R. obtusifolius after intense shoot competition and low interception of radiation was unexpectedly high. It is concluded that established dock plants cannot be controlled to any extent by strong competition of grasses, by variation in cutting frequency or by nitrogen fertilization. Effet de la fertilisation azotée et de la fréquence de coupe sur la compétitivité et la capacité de repousse de Rumex obtusifolius L. dans plusieurs pelouses de graminées Rumex obtusifolius L. est largement répandu, et il est considéré comme un problème majeur dans les prairies spermanentes intensives. Les effets de la fertilisation azotée (120, 240 ou 480 kg N ha^?1), de la fréquence de coupe (Chaque 4 ou 6 semaines) et des graminées en compétition sur le développement, la production de matière sèche et la croissance de la tige de Rumex ont étéétudiées en plein champ. Des jeunes plantes de Rumex ont été plantées dans des gazons purs de Lolium multiflorum Lam., Lolium perenne L., Alopecurus pratensis L., et Poa pratensis L. De tous les traitements, seul Lolium multiflorum entrave subtantiellement la croissance de R. obtusifolius. Les intervalles de coupe de 6 semaines sont plus favorables au Rumex que ceux de 4 semaines. Sa proportion du rendement en herbe passe de 2%à 120 kg N ha^?1 (moyenne des 3 gazons sans Lolium multiflorum), à 18%à 480 kg N ha^?1. La capacité de reproduction de Rumex est fortement influencée par l'espèce de graminée en compétition: pour le P. pratensis, le Rumex a développé jusqu'à 12,3 tiges avec inflorescence par plante et par an, et seulement 0,9 pour les parcelles L. multiflorum. Le potentiel de reprise de R. obtusifolius après une forte compétitivé aérienne et une faible interception des radiations a étéétonnamment élevé. On conclut que l'extension d'un Rumex installé ne peut être combattue par une forte compétition des graminées, la variation dans la fréquence de coupe ou la fertilisation azotée. Einfluss der Stickstoffdüngung und der Schnitthäufigkeit auf die Konkurrenz von Rumex obtusifolius L. in verschiedenen Grasbeständen Der Stumpfblättrige Ampfer (Rumex obtusifolius L.) stellt auf intensiv bewirtschafteten Dauerwiesen ein wichtiges Unkraut dar. Der Einfluss der Stickstoffdüngung (120, 240 oder 480 kg N ha^?1), der Schnitthäufigkeit (alle 4 oder 6 Wochen) und konkurrierender Gräser wurde im Freiland auf die Entwicklung, die Trockensubstanzproduktion und das Sprosswachstum von Ampfer untersucht. Junge Ampferpflanzen wurden in etablierte Reinbestände von Lolium multiflorum Lam., Lolium perenne L., Alopecurus pratensis L. und Poapratensis L. gepflanzt. Nur Lolium multiflorum vermochte das Wachstum von Ampfer wesentlich einzuschränken. Schnittintervalle von 6 Wochen förderten Rumex viel stärker als jene von 4 Wochen. Im Mittel der 3 Grasbestände (ohne L. multiflorum) stieg der Ertragsanteil von Rumex von 2% bei 120 kg N ha^?1 auf 18% bei 480 kg N ha^?1. Das Reproduktionsvermögen von Rumex wurde durch die konkurrierende Grasart stark beeinflusst, im Poa-pratensis-Bestand bildete Rumex 12,3 blütentragende Stengel pro Pflanze aus, im L. multiflorum-Bestand dagegen nur 0,9. Das Wiederaustrieb-svermögen von R. obtusifolius war nach intensiver Sprosskonkurrenz und niedriger Strahlungsabsorption unerwartet hoch. Aus den Ergebnissen ergibt sich, dass etablierte Ampfer-Pflanzen kaum durch konkurrenzstarke Gräser und durch die Änderung der Schnitthäufigkeit oder Stickstoffdüngung verdrängt werden können.     

Phytotoxicity of trifluoromethyl- and methyl-substituted dinitroaniline herbicides on resistant and susceptible populations of black-grass (Alopecurus myosuroides)

A Petri-dish assay was used to determine the phytotoxicities of the dinitroaniline herbicides pendimethalin, trifluralin, benfluralin and ethalfluralin, and the methyl-substituted analogues of the last three herbicides, on susceptible (Rothamsted) and multiple-herbicide resistant (Peldon) populations of blackgrass Alopecurus myosuroides Huds. The Peldon population showed a high degree of resistance to pendimethalin, which possesses a 3,4-dimethyl substitution. The two populations were equally sensitive to trifluralin, benfluralin and ethalfluralin which do not possess ring-methyl groups but contain a 4-trifluoromethyl group. Substitution of the 4-trifluoromethyl with a methyl group, as demonstrated by the analogues, reduced phytotoxicity, but to a much greater degree in Peldon than in the Rothamsted population. The study indicates that resistance to pendimethalin in the Peldon population is attributable to an oxidative degradation of the 4-methyl group, analogous to that which occurs with resistance to chlorotoluron. The lack of cross-resistance to the other dinitroaniline herbicides appears to be due to the absence of ring-methyl or other groups which are vulnerable to oxidative degradation, trifluoromethyl groups being particularly resistant to this form of reaction.     

Testing the performance of registered herbicides on the control of Campuloclinium macrocephalum (Asteraceae) in South African grasslands

We report on the performance of the registered herbicides picloram and metsulfuron‐methyl on the control of Campuloclinium macrocephalum (pompom weed) in grasslands. Herbicide trials in hydric and xeric grasslands were treated for three consecutive years in either summer (February) or autumn (April) and monitored for an additional 3 years after spraying ceased. Uncontrolled factors such as a host‐specific rust, fire and drought were observed from the second year of the study. Metsulfuron‐methyl and picloram did not differ in efficacy according to the timing of applications, but average mortality of marked plants was <80% expected of registered herbicides. Populations of C. macrocephalum in plots were reduced proportionately to the percentage mortality of marked plants. Picloram and metsulfuron‐methyl applied at 252 g a.i. ha^?1 and 45 g a.i. ha^?1, respectively, were not detectable by gas chromatography in the upper 25 cm of the soil profile during any of the sampling intervals from 0 to 56 days after treatment. Three annual applications of registered herbicide did not reduce C. macrocephalum successfully, and it is estimated that between five (summer) to seven (autumn) annual treatments are required to reduce weed density to <1 plant per plot (25 m²). Future research should focus on rust–herbicide interactions, the role of fire in seedbank management and fire as a treatment that could be integrated with chemical control.