Trevor K James

AgResearch · Forage Science

Seeking low environmental impact alternatives to chemical herbicides that can be integrated into a regenerative agriculture system, we developed and tested flat-plate electrode weeding equipment applying ultra-low-energy electric shocks to seedlings in the field. Better than 90% control was achieved for all species, with energy to treat 5 weeds m−2...

Weeds are increasingly documented with evolved resistance to herbicides globally. Three species have been reported as resistant in maize crops in New Zealand: Chenopodium album to atrazine and dicamba, Persicaria maculosa to atrazine and Digitaria sanguinalis to nicosulfuron. Despite knowledge of these cases, the distribution of these resistant bio...

Abutilon theophrasti Medikus is a declared ‘Unwanted Organism’ and has been subject to a control programme on 41 properties in Waikato, New Zealand since it’s discovery in 2011. In 2015 A. theophrasti seed was introduced into New Zealand as a contaminant in fodder beet (Beta vulgaris L.) seed and later found to have grown on at least 250 farms thr...

A government research grant and industry co-funding allowed us to briefly provide free tests of suspected cases of herbicide resistance using traditional seedling-based assays. Information about the service was disseminated through the Foundation for Arable Research and other weed management professionals. Between 2019 and 2022 we received 248 seed...

Seeking an easy-to-deploy, energy-efficient, non-herbicide weed control method, we tested a flat-plate electrode to apply pulsed electric microshocks (PMS) to a grass and four broadleaf weed species. The method can be deployed via a hand-held unit or as part of a fully automated system to control escape weeds in field crops. The effectiveness of th...

Soil associated with sea freight (shipping containers, flat racks and used machinery) arriving at New Zealand seaports was sampled for bacteria, fungi, nematodes, macro-invertebrates and plant seeds. Pseudomonads were selectively isolated, as several significant plant pathogens fall within this bacterial group. The mean and median sample weight col...

For decades, herbicides have provided easy-to-use, cost-effective weed management, but alternatives are desired. Consumer preference for chemical-free food, awareness of environmental impacts, regulation increasingly restricting agrichemical use, and increasing prevalence of herbicide resistance are forcing changes to weed management strategies....

Ripgut brome (Bromus diandrus) is a significant weed in arable systems with cereals being negatively impacted through yield reduction and contamination of harvested grain. There are limited herbicide options for its control, and reduction of the weed seed bank is a key part of its management. Ripgut brome seeds were incubated in three soils known t...

The use of cover crops can improve the environmental sustainability of intensive cropping systems. A five-year field trial was undertaken to evaluate the effect of multi-season cover cropping on weed suppression within a no-till spring-planted maize system in the Waikato region in New Zealand. Five cover crop treatments were compared: gland clover...

The prevalence of herbicide resistance in ryegrass (Lolium spp.) in the wine-growing regions in New Zealand is poorly understood. Cases of glyphosate, glufosinate and amitrole-resistant ryegrass were documented in a few vineyards in New Zealand in 2013, but there have been no regional surveys for resistance. To address this knowledge gap, 106 viney...

BACKGROUND Chenopodium album L. is a troublesome weed in spring‐planted crops, and different levels of ploidy have been documented for this weed species. A population of C. album has evolved resistance to dicamba. The level of ploidy and inheritance of dicamba resistance was studied in this population. RESULTS The resistant and susceptible individ...

Pastures represent about half of the global agricultural area and productivity losses from weeds are significant. The complex interactions between them and other pasture plants, livestock and the environment imply a need for innovative research that transforms pasture management. To this end, a horizon scan was conducted to identify relevant issues...

Leaching of herbicides in cropping soils not only impacts the groundwater sources but also reduces their effect in controlling weeds. Leaching studies were carried out in two cropping soils and two forestry biowaste media, wood pulp and sawdust with two herbicides, atrazine and bromacil in a packed lysimeter with simulated rainfall. The hypothesis...

Abutilon theophrasti Medik. was initially introduced into New Zealand in the 1940s. Despite its introduction approximately 70 years ago, A. theophrasti infestation in New Zealand has been naturalized to one region only, although climate-based simulation models predicted that A. theophrasti establishment could almost occur in all New Zealand agricul...

Herbicide-resistant weeds are a growing challenge in agricultural systems worldwide, leading to additional management costs and yield losses. Best practice management guidelines have been promoted for decades, yet incidences of resistance continue to increase. In New Zealand, herbicide resistance might be more widespread than commonly assumed. To r...

Despite an extensive history of research into herbicide resistance in New Zealand maize, some aspects remain understudied. Herbicide resistance was first detected in New Zealand in the 1980s in maize crops, with atrazine resistance in Chenopodium album L. and Persicaria maculosa Gray. Since then, Chenopodium album has also developed resistance to d...

To estimate the prevalence of herbicide-resistant weeds, 87 wheat and barley farms were randomly surveyed in the Canterbury region of New Zealand. Over 600 weed seed samples from up to 10 mother plants per taxon depending on abundance, were collected immediately prior to harvest (two fields per farm). Some samples provided by agronomists were teste...

The persistence and degradation of two common herbicides, atrazine and bromacil in two organic media, wood pulp and sawdust were compared with two soils. The hypothesis tested was that herbicide degradation will be faster in high organic matter media compared to soil. Degradation of two herbicides was carried out in four different temperature regim...

Weed management interacts with soil in many ways. Its primary aim of reducing the number and biomass of non-crop plants means that it simplifies agroecosystems, although it produces negative ecological and environmental outcomes including reducing soil health. At the same time weed management is utterly essential, as without it weeds would overrun...

The number of herbicide-resistant weeds is increasing globally. A successful management practice requires an understanding of how resistance traits are inherited. Weed scientists worldwide have investigated the mode of inheritance for herbicide resistance in weeds. Depending on the resistance gene/mechanism, varied patterns of inheritance have been...

Yellow bristle grass is a highly invasive annual C4 pasture weed that has spread rapidly through many New Zealand dairying regions via seed dispersal. Seven trials were conducted on roadsides infested with yellow bristle grass to evaluate natural and mower-assisted dispersal. To trap seeds, yellow sticky traps were laid out at various intervals bot...

Herbicide resistance has repeatedly developed under intensive herbicidal weed management regimes globally with 255 species having resistant biotypes. In New Zealand, since 1979, resistance was found in 13 taxa, with >25 herbicides in 8 chemical classes showing reduced effectiveness (i.e. HRAC groups A, B, C, D, F, G, H, N and O). Cases included wee...

Weeds not currently present in New Zealand constantly threaten our agricultural economy. The challenge for risk management is to identify potential hazards, prioritise them, evaluate the risks presented by the most important hazards, then develop and implement risk mitigation measures. James and Phillips (2019a) estimated the potential spread rates...

Previous work has: Recognised 24 weed species, not currently present in NZ, as key hazards to NZ dairy pasture production; estimated their potential New Zealand distributions; and developed methods for predicting their potential spread rates and economic impacts. The present report describes results from using those methods to estimate the hazards’...

Previous work for DairyNZ developed a simple model to simulate the spatial spread of insect and weed hazards through their New Zealand CMI maps in annual increments. The next phase of the project aims to formulate a method to predict the relative spread rates of hazardous weed species. Spread can occur in the model through natural dispersal and by...

Previous work for DairyNZ identified 24 weeds not present in NZ that would be hazardous to pasture production should they become established here. The potential NZ distributions of these hazards have been estimated, and an approach to evaluating their spread rates suggested. The present report proposes a method for estimating their economic impacts...

Organic soil amendments can be useful for improving degraded soil, but this increase in organic matter (OM) may influence adsorption of herbicides subsequently applied to the treated soil, even though the particle size of amendments and their nature differ from typical soil OM. In this study, a batch equilibrium method was used to measure adsorptio...

Variegated thistle can dominate north-facing slopes on North Island East Coast hill-country reducing pasture production and livestock carrying capacity. On a hill-country sheep and beef property near Gisborne, the herbicides 2,4-D + clopyralid were applied in early-May by knapsack in combination with a June aerial application of 2,4-D ester. This w...

Vulpia bromoides (L.) Gray (hair grass) is a serious grass weed of New Zealand cereal crops, contaminating seed and reducing yield. Optimal management of this weed may be achieved when the environmental factors that affect its emergence are well understood. Emergence may then be predicted and manipulated through land management techniques, e.g. thr...

Velvetleaf (Abutilon theophrasti) was accidentally introduced into New Zealand in 2016 and intensive efforts are being implemented to mitigate the risk of its naturalisation. This study investigated the possibility of velvetleaf plants surviving in maize fields following silage harvest in late summer and early autumn. Velvetleaf plants were grown t...

The presence of Setaria pumila in dairy pastures lowers feed quality and may cause grazing avoidance. More information is required about the germination biology of this weed to improve the effectiveness of control strategies. Base temperature and germination profile were determined on a thermo-gradient table. For emergence depth, seeds were buried a...

This document sets out a ten-year Pastoral Weeds Research Strategy as requested by the 2017 ‘Strategic Science Investment Fund’ Investment Committee. It was developed from: a. A review of key current pastoral weeds research worldwide; especially where there are solid links with AgResearch interests, b. A summary of existing research capability with...

Variegated thistle (Silybum marianum) is a large, spiny annual that often forms dense monospecific communities on dry ridges and sunny hillslopes. The owner of a typical Poverty Bay hill-country farm with persistent variegated-thistle infestations reported that winter applications of herbicide were ineffectual in the long term as more variegated th...

Chenopodium album is a troublesome arable weed species which has evolved resistance to dicamba in New Zealand. The objective of this work was to investigate the patterns of absorption, translocation and metabolism of dicamba in resistant and susceptible C. album populations. No significant differences in absorption by the two populations were measu...

Forty-four rhizobial isolates from New Zealand endemic Sophora species growing in natural conditions were characterised and the effectiveness of selected isolates with regard to growth and N2 fixation of different Sophora species was tested. Sequences for the housekeeping genes (concatenated recA, gln11 and rpoB) of the isolates were diverse but se...

Ryegrass, both perennial (Lolium perenne) and annual (L. multiflorum), can be weeds in other arable crops such as wheat (Triticum aestivum). They are generally removed using selective herbicides, but herbicide-resistant perennial and annual ryegrasses have been reported anecdotally. Perennial ryegrass seeds that were suspected to be herbicide resis...

The prevention of biosecurity threats is an international priority and the development of improved phytosanitary treatment technologies is part of New Zealand's biosecurity science strategy. Twelve temperature/time treatments were investigated as potential methods to devitalise weed seeds. Six weed species, Digitaria violascens, Eleusine indica, Le...

AgPest is a website (www.agpest.co.nz) that provides relevant, up-to-date and independent information on the identification and control of pastoral pests and weeds to support New Zealand farmers and rural professionals with decision making around pest and weed management. In addition, AgPest provides timely advice that will reduce the need for ‘fir...

Winter cover crops potentially have a number of positive production and environmental benefits on subsequent maize (Zea mays) crops. A field study was undertaken in 2016/17 to evaluate the effects of winter cover crop residues on the emergence and growth of weeds, required herbicide inputs, and yields of maize in comparison to a winter fallow. Weed...

Here we review published research on the costs of weeds to New Zealand’s pastoral, arable and forestry sectors, and propose an alternative dynamic approach for future research. The studies reviewed had little in common methodologically, often contained guesswork, or were outdated. Their aggregation resulted in a conservative estimate of the cost of...

Soil frequently occurs as a contaminant on numerous sea, land and air transport pathways. It can carry unwanted invasive species, is widely recognized as a biosecurity risk, and is usually strictly regulated by biosecurity authorities. However, little is known about relative risk levels between pathways, thus authorities have limited capability to...

Glyphosate resistance has been found in two populations of Italian ryegrass (Lolium multiflorum) following many years of glyphosate application in New Zealand vineyards. Dose-response experiments showed that both glyphosate-resistant Italian ryegrass populations had 10-fold levels of resistance to glyphosate compared to a susceptible population. Po...

One of the crucial factors in the evolution of herbicide resistance in weeds is the mode of inheritance. Experiments were conducted to determine the inheritance of glyphosate resistance in a population of perennial ryegrass (Lolium perenne) caused by restricted glyphosate translocation. First, the degree of dominance of the glyphosate resistance tr...

Noogoora bur (Xanthium strumarium) is a large, herbaceous, highly competitive annual weed of arable and horticultural crops which is subject to Regional Pest Management Plans in the Waikato and Bay of Plenty regions, New Zealand. A study with scarified burs showed that most plants emerged from 0-40 mm and none from 100 mm depth. Plants emerged afte...

In 2013, three populations of perennial ryegrass (Lolium perenne) and two populations of Italian ryegrass (L. multiflorum) from five vineyards in New Zealand were confirmed to be resistant to glyphosate. The level of resistance in four populations was almost 10-fold while one population of perennial ryegrass (Population O) had a level of resistance...

The first cases of weeds developing resistance to glyphosate within New Zealand have recently been reported and investigated. Both perennial ryegrass (Lolium perenne) and Italian ryegrass (Lolium multiflorum) populations have become resistant to glyphosate in several Marlborough vineyards due to many years of weed control using mainly just glyphosa...

This study examined if glyphosate-resistant populations of Lolium multiflorum and Lolium perenne from some New Zealand vineyards were still susceptible to glufosinate and amitrole. The response of plants of one glyphosate-resistant population of L. multiflorum, population A, and two glyphosate-resistant L. perenne populations, populations J and O,...

Background Perennial ryegrass (Lolium perenne) has developed resistance to glyphosate within New Zealand vineyards following many years of herbicide application. The objectives of this work were to confirm resistance within two populations obtained from affected vineyards and to determine the mechanism of resistance to glyphosate.ResultsPopulation...

In New Zealand vineyards, evolution of glyphosate resistance in perennial ryegrass (Lolium perenne) has been reported recently, and restricted translocation of glyphosate has been found in these resistant plants. Past research with other plant species has found that restricted glyphosate translocation is temperature dependent. Glasshouse dose-respo...

Seven strains, ICMP 19430T, ICMP 19429, ICMP 19431, WSM4637, WSM4638, WSM4639 and WSM4640 were isolated from nitrogen-fixing nodules on the roots of the invasive South African legume Dipogon lignosus (subfamily Papilionoideae, tribe Phaseoleae) in New Zealand and Western Australia, and their taxonomic positions were investigated by a polyphasic app...

Weed seeds, many of which are small and transportable, easily penetrate cracks in biosecurity systems. The strict biosecurity imposed from 1993 onwards has closed many of the known pathways. However, they now sneak in through novel routes, such as within the spiky leaves on the tops of pineapples. This was spotted in the early 2000s, when the weed...

Three quick tests were evaluated for detecting glyphosate-resistant biotypes of Italian ryegrass and perennial ryegrass. Biotypes of these two species were used that were 13.4 and 7.3 times more resistant to glyphosate, respectively, than susceptible biotypes when assessed using a sprayed pot study. One assay exposed germinating seeds of resistant...

A quick test was developed using seeds in petri dishes to detect resistance to dicamba in fathen (Chenopodium album L.) which has developed in some maize fields in Waikato, New Zealand. Seeds were collected from four Waikato maize fields (populations A, B, L and M) where dicamba has been applied for many years, and also three sites (populations C,...

Tradescantia fluminensis, Plectranthus ciliatus, Asparagus scandens, Hedera helix, Lamium galeobdolon and Selaginella kraussiana are all mat-forming invasive species that limit regeneration of native plants in forest remnants in New Zealand. Experiments using potted specimens of these weeds showed that low rates (338-675 g/ha) of the herbicide tric...

Maize silage is an important dairy feed supplement and is often transported many kilometres from where it is grown to where it is ensiled. Debris has been observed to blow from the transporting trucks as they travel along the road, raising concerns about the spread of weeds. In this study, trucks carrying freshly chopped maize were intercepted as t...

Tutsan (Hypericum androsaemum) is a highly invasive semi-evergreen shrubby weed found throughout New Zealand. Described as a serious pasture weed in 1937, it has been held in check for many years by tutsan rust. Recently it has spread rapidly into pasture, forestry and conservation areas. Present methods available for managing tutsan are proving in...

Chilean flame creeper is a summer active perennial vine growing to 5 m or more It has an extensive rhizomatous root system and has proved very difficult to control with herbicides Both the above and below ground stems are soft without any tough outer skin or bark For these studies plants were grown in 50 litre tubs in Waikato and Southland and four...

The Chatham Islands possess several endemic vertebrate invertebrate and plant species and are free of many pests found on mainland New Zealand Keeping out unwanted organisms that may threaten the agricultural sector on the islands is important for the local economy Research found that soil intercepted from used machinery destined for the Chatham Is...

Tutsan (Hypericum androsaemum) is a highly invasive semi-evergreen shrubby weed found throughout New Zealand. Described as a serious pasture weed in 1937, it has been held in check for many years by tutsan rust. Recently it has spread rapidly into pasture, forestry and conservation areas. Present methods available for managing tutsan are proving in...

Seven strains, ICMP 19430T, ICMP 19429, ICMP 19431, WSM4637, WSM4638, WSM4639 and WSM4640, were isolated from nitrogen-fixing nodules on roots of the invasive South African legume Dipogon lignosus (subfamily Papilionoideae, tribe Phaseoleae) in New Zealand and Western Australia, and their taxonomic positions were investigated by using a polyphasic...

Sorption of pesticides in soil is often time-dependent, with increasing adsorption with time. This time-dependent sorption kinetics can lead to groundwater concentrations that are significantly different from those predicted using an equilibrium adsorption model such as that employed in the U.S. EPA PRZM-GW model. Currently, the U.S. EPA is revisin...

A dose-response experiment was conducted on a previously confirmed glyphosate resistant perennial ryegrass (Lolium perenne) population from a Marlborough vineyard to examine if it is also resistant to amitrole after an initial experiment suggested amitrole is less effective on this population. The plants of two populations of perennial ryegrass, Po...

The South African invasive legume Dipogon lignosus (Phaseoleae) produces nodules with both determinate and indeterminate characteristics in New Zealand (NZ) soils. Ten bacterial isolates produced functional nodules on D. lignosus. The 16S ribosomal RNA (rRNA) gene sequences identified one isolate as Bradyrhizobium sp., one isolate as Rhizobium sp....

The expansion of atrazine-resistant Chenopodium album (common lambsquarters) since the 1980s has forced New Zealand's maize-growers to use an additional postemergence herbicide application. The frequent use of dicamba for this has selected for a common lambsquarters population with reduced sensitivity to dicamba. Initial greenhouse experiments with...

To quantify soil residual activity and plant-back periods for two maize herbicides, saflufenacil and topramezone, different rates were applied to a cultivated soil and samples (0-5 cm) collected at regular intervals for glasshouse bioassays. Phytotoxic residues of saflufenacil applied at 17 g ai/ha, the rate used for conservation tillage and pastur...

Identification of weed seeds from overseas countries can be problematic, particularly when diagnostic tools are lacking or incomplete. A well trained seed analyst will usually be able to identify seed to generic level but not always to the species level. Resources for identification of mature plants are usually more complete. Using a seed germinati...

A doseresponse experiment was conducted on a previously confirmed glyphosate resistant perennial ryegrass (Lolium perenne) population from a Marlborough vineyard to examine if it is also resistant to amitrole after an initial experiment suggested amitrole is less effective on this population The plants of two populations of perennial ryegrass Popul...

To assist with managing the outbreak of resistance to dicamba that has developed within fathen (Chenopodium album L.) in New Zealand maize fields, a quick test has been developed using seeds. As dormancy of the seeds initially hindered development of a quick test, experiments showed that this can be overcome by removing the perianth from each seed,...

Plants were obtained from two populations of Italian ryegrass (Lolium multiflorum) and three populations of perennial ryegrass (Lolium perenne) from different vineyards in Marlborough and Nelson that were suspected of being resistant to glyphosate following many consecutive applications of this herbicide over recent years. Each population was multi...

The eficacy of the herbicide fenoxaprop for control of yellow bristle grass (Setaria pumila) in pasture was evaluated in two ield trials. Additionally, glasshouse experiments investigated its phytotoxicity on seven annual and four perennial C4 grass species. Results of the ield trials showed good control of yellow bristle grass and consequently a v...

Many legumes can colonise low nitrogen (N) soils due to their ability to fix atmospheric N2 via symbiotic bacteria in root nodules. Galega officinalis and Hedysarum coronarium are legumes that have naturalised and become common weeds in New Zealand. Previous work outside of New Zealand indicated that they only form effective nodules with their resp...

Thirty-nine Waikato dairy pastures have been surveyed annually each February, for 5 years, to quantify changes in cover of yellow bristle grass and to determine if management factors influence this. After a severe drought, yellow bristle grass ground cover increased from 4 to 11% (2008 to 2009) and has since remained at this level. Ryegrass cover d...

Successful management of weed infestations requires an understanding of their biology including seedbank longevity. The controlled ageing test used by the Millennium Seed Bank, Kew Gardens, was evaluated for several grass and broadleaf weed seeds. The method aims to estimate seed longevity from a seed survival curve, using a controlled environment...

Butterprint (velvetleaf in many countries) is one of the worst broadleaf weeds in maize (Zea mays) and soya bean (Glycine max) crops in USA. It has been accidently introduced into New Zealand on several occasions. Recently it has been found in three maize fields in Waikato and has become well established at one 20 ha site. Twelve different post-eme...

A used stump grinding excavator was imported from Bathurst Australia into New Zealand via the Ports of Auckland The excavator was subject to water blasting to remove soil contamination Prior to cleaning soil was taken from one of the tracks (26 g) and grinding head (a subsample of 2140 g) to determine nematode and seed numbers and diversity The pre...

This is a full colour identification guide for a wide audience, from the same publisher that produced An Illustrated Guide to Common Weeds of New Zealand. Features include an easy-to-follow format, with keys for each category (grass, sedge, rush) to aid identification, excellent colour photographs throughout, and a fully illustrated colour glossary...

URL: http://www.landcareresearch.co.nz/resources/identification/plants/flowering-plants-key There are currently 1075 genera in the key, and the key uses 56 features to identify them. The key is illustrated with 9000 images, showing a representation of each genus and the features used to identify them. The key links to Ngā Tipu o Aotearoa, Landcare...

Chilean flame creeper (Tropaeolum spe-ciosum) is a perennial vine with slender stems which coil around objects, allowing the plant to climb. It has delicate five-fingered leaves and scarlet, spurred flowers that are about 4 cm across, followed by blue berries. It also has an underground structure of rhizomes which can spread widely through the loos...

Dissolved organic matter (DOM) is defined as the organic matter fraction in solution that passes through a 0.45 μm filter. Although DOM is ubiquitous in terrestrial and aquatic ecosystems, it represents only a small proportion of the total organic matter in soil. However, DOM, being the most mobile and actively cycling organic matter fraction, infl...

Corn gluten meal (CGM) is an approved organic fertilizer and pre-emergence herbicide that can be manufactured in the form of grit. This grit was tested for its ability to abrade seedlings of the summer annual weedy grass, Setaria pumila, when plants were in the 1- to 5-leaf stages of growth. CGM was propelled at air pressures of 250–750 kPa at dist...

The recently developed herbicide saflufenacil was evaluated in six field trials, between 2008 and 2011, for weed control in maize (Zea mays) crops. Trial sites varied considerably in soil characteristics and weed spectrum. No phytotoxicity or visual damage symptoms were observed in any of the six cultivars planted. When used alone at 70 or 105 g ai...

The wild type of broom corn millet (Panicum miliaceum) is a serious emerging weed, currently prevalent in New Zealand sweet corn (Zea mays) crops. This study shows its seed is nearly twice the weight of other common grass weeds and can germinate in the temperature range 16-34°C, with 50% germination at 26°C and greatest germination occurring at 31°...

The persistence of residual herbicides used in maize (Zea mays) silage crops was investigated in three field trials located in Waikato, Taranaki and Canterbury. Herbicides used included atrazine and acetochlor applied pre-emergence and mesotrione and nicosulfuron applied 6-12 weeks after planting. Bioassay of soil samples collected about the time o...

Tribenuronmethyl is a sulfonylurea herbicide for control of certain broadleaf weeds in cereal crops and prior to conservation tillage Safe plantback periods for this herbicide are expected to be shorter in acid soils compared to neutral or alkaline soils due to a faster rate of degradation at low pH levels This research was conducted to determine t...

In 2007, Dow Agrosciences New Zealand Ltd registered Triclopyr triethylene amine in New Zealand for use in wetlands and aquatic sites. Its registered name is Garlon ® 360. This report outlines pot trials and field trials (Waikato River Delta, island on the Waikato River near Rangiriri, South Taupo Wetland near Turangi and Cockayne Wetland in Christ...

There have been numerous changes in botanical names of New Zealand weeds and their assignment to plant families since the publication of the relevant Flora of New Zealand volumes. This paper outlines the reasons behind the changes in nomenclature, including the recent use of DNA sequencing to classify plants by the Angiosperm Phylogeny Group (APG)....

Poor pasture persistence and ingress of weedy species are major concerns for farmers. The seedbank gives an indication of what weedy species may establish in pastures and compete with sown species. It was hypothesised that the above-ground composition reflects the seedbank. The seedbank was sampled and botanical assessments were undertaken during O...

The efficacy of several pre-emergence herbicides on barnyard grass (Echinochloa crus-galli), smooth witchgrass (Panicum dichotomiflorum) and yellow bristle grass (Setaria pumila) was investigated in different soils in pot experiments. These soils were collected from the top 10 cm of seven maize fields with different cropping histories. The herbicid...

Some herbaceous broadleaf weed species are major weeds of pastures and are difficult to manage with ongoing re-infestation from the persistent soil weed seedbank. In this study, seeds from five weed species were collected in 2009 from two sites where they had been buried at three depths since 1981. The species were Scotch thistle (Cirsium vulgare),...

Field horsetail is a perennial, rhizomatous weed with summer-growing fern-like foliage and sporelating stems. It likes moist, free-draining sandy soils and gravel riverbeds and flood plains. Glasshouse experiments on 10-month old potted field horsetail plants showed excellent efficacy of imazapyr, amitrole, metsulfuron, picloram and combinations of...

URL: https://www.landcareresearch.co.nz/resources/identification/plants/weeds-key This Lucid 3 key is for the identification of more than 600 taxa (species, subspecies, varieties, hybrids and cultivars) including the Department of Conservation consolidated list of environmental weeds in New Zealand (Howell, 2008), the National Pest Plant Accord (...

Pot experiments evaluated the efficacy of several pre-emergence herbicides on three annual grasses that are major problem weeds in most maize growing regions. Herbicides evaluated included alachlor, metolachlor, dimethenamid, two formulations of acetochlor, and proprietary mixes of acetochlor with atrazine or metribuzin. Pots were filled with soil...