Posts in weed management
For best weed management you must know what you are dealing with

To successfully manage weeds, pests or diseases they must be correctly identified. Mis-identification leads to incorrect control practices which is costly and often makes the problem worse.

Fallopia convolvulus flowers and fruit.

Fallopia convolvulus flowers and fruit.

Many people still rely on common names of weeds for their identification, however this leads to problems because many species have multiple common names.  Some names are only used within some states or even districts such as Fallopia convolvulus which is known as climbing buckwheat in Queensland and black bindweed in New South Wales.

A more interesting example is Conyza sumatrensis which is normally called tall fleabane. However on the north coast of New South Wales it is often known as cobbler’s pegs. Cobbler’s pegs are actually Bidens pilosa which look totally different.

Originally the naming of plants and animals was based on where they came from. For example any animal from the sea was called a fish. This included whales and dolphins. Many Australian plants were given English names because the colonisers had a European world view. For example the tallest flowering tree in the world - Eucalyptus regnans – was called mountain ash. It looks nothing like European ashes (Fraxinus spp.).

Our modern naming system of genus and species comes from Carl Linnaeus (1707-1778) who divided flowering plants into groups depending on their flowers and fruits.

 Unfortunately identifying plants by flowers and fruits is too late for most management strategies. Therefore it is good to use vegetative characteristics to identify plants. This has the major benefits of early weed identification which are cost effective allowing timely management strategies to be implemented.

Starting point for identification

Land plants are divided into groups of increasing complexity in structure, particularly the vascular tissue and how they reproduce and spread. It is generally accepted that land plants commence with green algae and goes through to the flowering plants.


  • Green algae - contain chlorophyll, no roots or vascular tissue

  • Mosses & liverworts - have absorbing organs, not roots

  • Club mosses - single veins in small leaves, and union of stem and leaf without a break in the vascular tissue of the stem. Reproduce by spores.

  • Horsetails - hollow, jointed stems, reproduce by spores and have an extensive root system

  • Ferns - highly dissected leaves which unroll from the tip, reproduce by spores and often have rhizomes

  • Gymnosperms - seeds borne upon scales in a cone or as a naked seed - cycads, ginkgo, conifers

  • Angiosperms - flowering plants - seeds enclosed in a seed case or ovary – monocotyledons and dicotyledons

The starting point to narrow down and identify the majority of weeds (flowering plants) is to figure out whether they are monocotyledons or dicotyledons. It is also handy to know over half of weeds come from 5 families of flowering plants - Asteraceae, Brassicaceae, Fabaceae, Poaceae (monocot) and Iridaceae (monocot).

Monocotyledons can be identified by the following characteristics:

  • plants are herbaceous (no woody parts)

  • single seed leaves

  • leaves lack a leaf stalk, with each leaf consisting of an upper strap-like blade and a sheathing base that encloses the stem

  • ligule on the upper leaf surface is membranous or hairy

  • leaf veins are parallel with no single main vein

  • roots are fibrous

  • includes the major families Poaceae, Liliaceae, Cyperaceae, Orchidaceae, Iridaceae, Amaryllidaceae and Alliaceae


  • two seed leaves (cotyledons)

  • shoot system consisting of:

    • main axis (stem)

    • leaves attach to the stem at nodes

    • each leaf consists of lamina, leaf stalk (petiole) and strongly developed main vein with lateral veins (reticulate)

    • buds in leaf axils and / or at the end of stem

  • Root system - primary or tap root, with lateral roots

 Plant – environment associations

Knowing the types of environment in which certain weeds like to grow can help narrow down the possible candidates. Weeds like annual ryegrass however will grow over a range of environments. Some examples are given below.

Acidic soils prone to waterlogging in winter

Docks (Rumex spp.), rushes and toad rush (Juncus spp.), sedges (Cyperaceae), loosestrife (Lythrum spp.), crassula (Crassula spp.)

Lighter textured, acidic soils

Capeweed (Arctotheca calendula), matricaria (Oncosiphon piluliferum), Geranium spp., Erodium spp., sorrel (Acetosella vulgaris), annual ryegrass, Vulpia spp., wild radish (Raphanus raphanistrum), Paterson’s curse (Echium plantagineum), Indian hedge mustard (Sisymbrium orientale).

Lighter textured, alkaline soils

Capeweed, skeleton weed (Chondrilla juncea), brome grass, annual ryegrass, wild turnip (B. tournefortii), spiny emex (Emex australis), medics, rough poppy (Papaver hybridum)


Fumitory (Fumaria spp.), deadnettle (Lamium amplexicaule), turnip weed (Rapistrum rugosum), charlock (Sinapis arvensis), variegated thistle (Silybum marianum), parodoxa grass (Phalaris parodoxa)

Collecting plants for identification

It is always a good idea to collect specimens for correct identification. There are plant identification services at the various State herbaria. If it is a new species for an area there will often be no charge however if it is a common weed or plant there will be a fee.

See how to collect and prepare specimens for identification here.

How to photograph a plant to get an accurate identification

With smart phones being ubiquitous technology everyone has the tools to take great photos, but it is annoying to receive blurry images someone expects you to give a miraculous ID from.

Firstly make sure that your images are in focus! Take a series of images. Include the whole plant then get close enough to show detail. Don’t have the subject mixed in with lots of other plants. Isolate the plant you want to photograph from the background or other plants.

You also want light on the front of the subject and not have bright light or reflection behind the subject. Include an object to give an idea of size – fingers, coin etc..

Finally you actually want a flower/seed head and a leaf and stem in the image. These must be in the same plane (side-by-side) otherwise something will be out of focus.

An effective technique is to hold the leaf/stem and flower/seed head up to the sky at arms length with the sun behind you. The image will be in focus, well lit and have necessary detail to allow identification.

Include information with the images - location, soil type, vegetation association, and plant habit – annual, perennial, tree, shrub, herb or vine.

For further information on weed identification

Online Australian herbaria

Atlas of living Australia

New South Wales Royal botanic Gardens – Flora online

FloraBase – the Western Australian flora

Flora of Victoria

Seeds of South Australia

Weed identification websites

Weeds in Australia weed identification tool

Environmental weeds of Australia – Biosecurity Queensland edition

Weeds of Australia identification tool


Weeds of Western Australia Group - a group of keying weed people desperate to identify your weeds -

Plant Identification Australia Group - a keen group of plant people ready to give you an ID


Club moss - an early type of green plant that reproduces by spores.

Club moss - an early type of green plant that reproduces by spores.

Phalaris paradoxa 1.5 leaf - a monocotyledon

Phalaris paradoxa 1.5 leaf - a monocotyledon

Two cotyledons of Fumaria spp. with first true leaf beginning to emerge.

Two cotyledons of Fumaria spp. with first true leaf beginning to emerge.

Spiny rush along the edge of the Hunter River, NSW.

Spiny rush along the edge of the Hunter River, NSW.

Acidic sands on the WA south coast favours Actotheca calendula

Acidic sands on the WA south coast favours Actotheca calendula

Spear thistle favoured by higher phosphorus levels which in turn favours clover growth and nitrogen fixation

Spear thistle favoured by higher phosphorus levels which in turn favours clover growth and nitrogen fixation

Southern Alberta Weed workshop - Transdisciplinary approaches to better weed research and management?

In June 2016 Sally Peltzer & I attended Andina III – a 5 day weed workshop in southern Alberta organised by a range of weedies including the notable Roger Cousens, University of Melbourne and Sonia Graham, a social scientist from the University of NSW.

The workshop was held at the Gladstone Ranch near Pincher Creek, in the eastern foothills of the Canadian Rockies and was attended by 32 ‘natural’ and 'social' scientists, agronomists and consultants, from seven countries. Australians and North Americans made up the bulk of the participants.

 Gladstone Ranch homestead

This was the third Andina workshop, with the first 2 taking place in Yellowstone National Park and Spain. Each conference has had a different theme. The theme for Andina III was “the transdisciplinary approach” to weed research and management and a few social scientists were thrown into the mix.

The general principle behind these get-togethers is to fill a perceived void left by traditional conferences by fostering international dialogue, collaboration and mentoring in a relaxed atmosphere. By spending 5 days together and doing a wide range of activities trust and relationships are built between the participants which will continue into the future once everyone has returned home to their normal lives and jobs.

So what is a "transdisciplinary approach"?

This was an interesting question because we asked “what is the difference between transdisciplinarity and a good research and extension program?” This was discussed at some length, for better or worse over the five days.

Integrative multidisciplinary research is thought to address complex real-world problems addressed systemically rather than as isolated problems.  It involves harnessing scholarly and practical knowledge across many stakeholder groups such as scientists from different disciplines, private sector players, farmers, and extensionists at a range of geographic and political levels e.g. local, regional, landscape-wide.

Some of the participants in a 'break-out' session.

Multiple parties bring:

  • a wide range of knowledge to address a complex problem.
  • AND a diverse and often conflicting range of interests and views

Normally what happens in research is that researchers concentrate on research directions and objectives and tack on some publicity, such as a dry press release, or ill-planned extension at the completion of the research. This is the old top-down approach to research - we know what’s good for you so you should use our research findings....... and be grateful while you’re at it.

We tried to test the multi-disciplinary approach in southern Alberta by doing a fair amount of pre-workshop communication between workshop members as well as reading up on the issues facing the diverse range of land users in southern Alberta.

For us the most interesting case study we investigated was the Waldron Grazing Cooperative which:

  • Is a collection of commercial cattle ranches  (over 16,000 ha) under a single progressive manager
  • It is a prime wildlife corridor for bears, cougars, elk, deer, coyote and moose
  • Accesses land management funds for projects from Alberta Province and Federal Government, private donors and the co-operative.
  • Has an agreement with the Nature Conservancy of Canada to protect the land in a state similar to that prior to white settlement, except running beef instead of bison.
  • Makes the Waldron Coop an outlier with other beef ranchers in the area because they are seen as different because of their size and the way they access a range of external funds. This is then seen as the major reason why they can run above district average numbers of beasts and obviously has nothing to do with the pasture and grazing management being practised.
  • Has leafy spurge (Euphorbia esula) as its major weed species. Leafy Spurge is a perennial with a spreading root system that isn’t eaten by cattle and has been spreading across North America since the early 1900s.

Mike the Walrond manager’s approach

Mike, manager of the Waldron Cooperative, outlining his approach to range management.

  • Manage the grass first and the cattle second because without the grass you can’t fatten the cattle. Mike tries to emulate the grazing patterns of the bison with rotational grazing and lets the perennial grasses seed before winter to maintain species diversity in his pastures. Like in Australia most cattle ranchers set stock their pastures over summer leading to an increased density of leafy spurge, and a decline in species diversity and cattle weight gain.
  • To manage the leafy spurge Mike uses a biocontrol agent that is a root-feeding beetle. Many other ranchers have also established this beetle on their leafy spurge infestations while others use an ‘unplanned’ herbicide program in an attempt to contain weed infestations.
  • What is different with the Waldron Co-op is that they graze  sheep (leased) on the spurge as well. We were told that the reason why the combination of biocontrol and grazing with sheep works so well was that the sheep disperse biocontrol agent. Interestingly no research has been conducted looking at the influence of defoliation in combination with the root feeding biocontrol. We thought that this is probably the reason why this combination works so well not the dispersal of the beetles. This is an excellent example where a multi-disciplinary approach to a problem would have paid off rather than leaving it to biocontrol specialists.

  • It is interesting to note that there also is a VERY negative attitude towards the grazing of sheep in the general ranching community going back to the time when homesteaders moved into the Canadian rangelands leading to ‘range wars’.  
  • We thought that if you hate sheep, why not try a combination of slashing and biocontrol?

Unfortunately we did not meet any other ranchers that would be considered “typical”. The ranchers we sat down and discussed a weed management with were all organic beef growers. What all ranchers do seem to like doing is sit on a horse.

Canada has also experienced contraction of provincial agriculture departments with a reduction in production research and extension being available to landholders.

So what did we take home from Andina III?

  • Andina is a great opportunity to meet a range of international researchers and get to know them having a great time while you’re at it.
  • Multi-disciplinary approaches (which are hard to define – just read the peer reviewed papers on the subject) have merit because a number of the researchers we met did not work with anyone from outside their technical silo. Hmmmm. Several researchers said that they would not look at multi-disciplinary cooperation because it would not progress their career objectives i.e. pump out papers.
  • Multidisciplinary teams seem an obvious approach for someone with an extension/research background but was a new concept for a number of the researchers.

If you get the opportunity to attend an Andina workshop it is well worth the effort. The next workshop is in Agentina in January 2018. This time the topic will be fundamental molecular biology through to mathematical modelling. For more information go to

Being aware of sensitive crops and (geographical) areas when spraying

There has been rain and that means it’s weeds and spraying time. This time of year also lends itself to extremely risky spray conditions. Beautiful autumn weather is when surface temperature inversions are most common. For more information on inversions read my previous blogs here and here.

Strong inversion conditions March 2016. Image: AGRONOMORemember that all pesticides drift, it is just that some, such as Group I herbicides like 2,4-D, have a recognisable odour and produce unique symptoms on sensitive vegetation.


So what is the problem with off-target movement of pesticide? The most obvious agricultural issue is damage to sensitive crops. For example in the 2007-08 cotton growing season it was estimated that 10 per cent of the Australian cotton crop has some level of herbicide damage costing $5 million.

The second agricultural issue is pesticide residues. Organic farmers certainly don’t want anyone else’s pesticides. Drift is a particular problem when a crop is getting close to harvest. Signing a vendor declaration that you haven’t used certain pesticides gets complicated when the purchaser tests the product and it is ‘contaminated’.

Some of our major trading partners also have zero tolerance for certain pesticides. Ship loads of grain have been turned around and sent back for such breeches. The wine grape industry is particularly aware of the potential effects of unwanted residues on their markets.

Contamination of the natural and human environments is also a major concern.

Sensitive areas

Other than showing a duty of care, reading and following the label, using buffer zones and using best practice application, we need to be aware of sensitive areas in the vicinity of the farm when spraying. Talk to your neighbours and find out what crops they will have in, particularly in paddocks along the boundary. Be aware of state restrictions on pesticide use and spraying.

Some Australian states have restrictions on spraying in or near ‘sensitive’ areas. Western Australia has listed most Group I herbicides as ‘Scheduled’ meaning they cannot be used within certain distances of sensitive crops and high volatile 2,4-D ester is banned within 5 km of a commercially sensitive crop (vineyards or tomatoes), within 19 km of the Geraldton post office and within the Swan Valley, or within 10 km of the Kununurra Post Office. High volatile ester is not registered any other state or territory.

Victoria has nine designated areas where the type of pesticide and its application is regulated.

Agricultural Chemical Control areas in Victoria. Source: Agriculture VictoriaThe cotton industry has led the way with on online mapping with 95% of cotton crops mapped.  There is no excuse to say you didn’t know there is cotton nearby.

Cotton field awareness map for the western Riverina. Source: Cotton Australia & Cotton CRDCWestern Australia also has a voluntary system of registering your pesticide sensitive crop with the Department of Agriculture & Food WA.

DAFWA sensitive areas map 2015The map highlights organic farms, vineyards, tree crops, vegetable, bee hives and aquaculture sites. Being voluntary not all WA sensitive crops are mapped and a quick comparison with Google Earth will show additional vineyards and orchards. Another problem is that most broadacre farmers I have spoken with are unaware that this map of sensitive crops exits.  This is ironic because much of the potential drift affecting these sensitive crops could come from cropping country.

When it is spray time, do some planning, look at the weather forecast and for any potential risks, talk to your neighbours, use the right gear and get that pesticide where it is meant to be.

Why herbicide resistance tests don’t always reflect paddock experience

Some growers and agronomists feel the results from herbicide resistance testing services don’t accurately reflect what is happening in the paddock. Some samples are coming back susceptible to the tested herbicides while the farmers are finding poor control in the paddock.

Glyphosate resistant annual ryegrass in winter fallowThis phenomenon was investigated in northern NSW in 2008 where there were differences between in-paddock control of wild oats compared to the testing service results. What came back as susceptible in the “lab” tests were still not being well controlled in the field. So what is going on?

Differences occur due to:

  1. Sampling
    How were the samples taken? From one spot in the paddock, several dense patches or averaged over the whole paddock. Different sampling methods will give different test results. This needs to be known by whoever is interpreting the test. 90% resistance in one patch can be quite different to 5% resistance is a bulked sample from across the paddock. Results are only as good as the original sampling.
  2. Differences in herbicide coverage between field and lab
    Testing services spray the weeds in spray cabinets using 110° 01 twin jet nozzles. These nozzles produce a very fine to fine droplet spectrum and under the controlled conditions of a spray cabinet give excellent coverage. If a grower tried this at least half of the herbicide would not reach the target.
    Spray application by the grower has to contend with widely varying temperatures, humidity, wind, droplet interception by stubble and crop, much higher travel speeds, varying boom height and potential moisture and temperature stress of the target weeds.
    By necessity growers use coarser spray quality and often lower application volumes giving less than 15% coverage compare to the lab’s over 40% coverage. Add to this herbicide rate, adjuvant, water quality there is no wonder there are differences.
    Testing pre-emergent herbicides such as atrazine add another layer of complexity. Due to atrazine’s high water solubility the composition of the potting mix and level of watering by the testing service can make huge differences to the results. Too much watering can leach the herbicide from the pots. Add to this atrazine’s sensitivity to light, insufficient light means the herbicide doesn’t work, giving a false positive to resistance.

Blank pots were susceptible samplesBottom line

If an Australian testing service says you have resistance, you have resistance. No doubt about it. What that means to you as a grower or adviser is:

  • Make sure you take a representative sample.
    Seed from a harvest sample is more likely to be an average. Take some photos of the infestation and send them in with the samples so the service can give you some more accurate advice.
  • So you have resistance? But do you know which herbicides still work?
    Next time think more broadly and test for susceptibility.
  • Make sure you use the best spray application techniques available to you and don’t cut corners. Poor application will only make ALL of your weed problems worse!