What is the real story behind pH and hardness of spray solutions?

The quality of water being used in the spray tank to act as the carrier for your pesticides can have significant effects on how well those pesticides will work. It is surprising however to find that very few growers have had water quality tested.

Obviously, water that is free of suspended materials such as clay, algae and other debris will block filters and possibly nozzles which makes spraying very frustrating. However, there are a range of water quality variables unseen to the naked eye that can affect certain pesticide formulations. The two that cause the most confusion are hardness and pH.

Water hardness

Water that is considered hard has high levels of calcium, magnesium or bicarbonate ions. Calcium and magnesium ions have positive electrical charges that enable them to bind with negatively charged products such as ‘weak acid’ herbicides in solution making them less soluble. Extreme cases can lead to the herbicide settling out in the spray tank or most commonly reducing the ability of the active ingredient to be absorbed through the plant leaf. Example of weak acid herbicides include glyphosate and amine formulations of 2,4-D, MCPA, 2,4-DB, clopyralid and diflufenican.

Water hardness above 250 to 350 parts per million (ppm) (calcium carbonate – CaCO3 equivalents) should be treated before adding weak acid herbicides.

The cations that can cause the most trouble for pesticides include:

  • aluminium (Al+++)

  • iron (Fe+++, Fe++)

  • magnesium (Mg++)

  • calcium (Ca++)

  • sodium (Na+)

With magnesium and calcium being the most common cations causing water quality problems, aluminium can be a problem if alum (aluminium sulphate) has been used to remove (flocculate / settle-out) clay and other particles from the spray water.

Bicarbonates can also affect herbicides such as Group A ‘dims’ (e.g. clethodim) and 2,4-D amine at levels as low as 175 ppm. Bicarbonates are not detected by standard water hardness tests and must be tested for separately, to total hardness. Groundwater from areas with lots of limestone can be high in bicarbonates. Water high in bicarbonates can be overcome by substituting MCPA or a low volatile ester formulation of 2,4-D for the 2,4-D amine. Group A ‘dim’ herbicides can be helped with the use of ammonium sulphate.

To treat water for hardness and bicarbonates, use up to 1% crystalline ammonium sulphate or liquid formulations of ammonium sulphate such as a Liase®.

Water pH

The pH of a liquid is a method of describing how acid or alkaline the liquid is. A neutral pH is about 7 whereas a pH of 2 is very acidic and a pH of 14 is very alkaline. It is important to remember that the pH scale is a log scale. This means that a value of 6 is 10 times more acid than a pH of 7 while a pH of 8 is 10 times more alkaline than 7 and 100 times more alkaline than 6. The table below give some examples of common materials and their pH.

Table 1. pH values of some common substances.

pH

Substance

14

Sodium hydroxide (caustic soda)

12.6

Sodium hypochlorite (bleach)

11.5

Ammonia

10.2

Magnesium hydroxide (antacids)

9.3

Sodium borate (borax)

8.4

Sodium bicarbonate (baking soda)

8.1

Sea water

7.4

Human blood

7.0

De-ionised water

6.8

Tea

6.7

Milk

6.0

Rain water

4.5

Tomatoes

4.2

Orange juice

4.0

Wine & beer

2.8

Vinegar

2.2

Lemon juice

2.0

Stomach acid

1.0

Battery acid

0.0

Hydrochloric acid


There are many half-truths in the marketplace about the effect of pH on pesticides. It is well recognised that pH above 8 will reduce the life in the tank of certain pesticides such as organophosphate insecticides. Despite this, the effect of high pH on herbicides is largely overstated.

Glyphosate has been found to work slightly better in moderately acid solutions, but this effect is from the precipitation of calcium compounds before forming calcium glyphosate on drying of the droplets on the leaf. Treat the water with ammonium sulphate before adding glyphosate and you solve this issue.

If the pH of water used in the spray tank is between 6 and 8 it is suitable for spraying.

Acidic water (pH < 5) can affect the stability of mixes (Figure 1) and lead to gelling of salt-based products and has been found to increase the volatility of herbicides such as dicamba.

This grower was told to drop the pH of his spray. He added citric acid and added another three products. Source: R. Buttimor

This grower was told to drop the pH of his spray. He added citric acid and added another three products. Source: R. Buttimor

Water above pH 8 can modify droplet contact on the leaf surface, reduce stability of mixes and change product solubility.

So, do I need to reduce the pH of my water?

If your water is between a pH of 6 and 8 the answer is no.

Something that is rarely discussed is that the addition of the pesticide will modify the pH of the solution. Therefore, each pesticide user needs to test the water before the addition of pesticides and then check the pH after the addition of the pesticide. They will be very different.

The addition of glyphosate to the spray solution will drop the pH of the spray mix from 8 to less than 5. In Figure 2 below the test strip on the right is town water which normally has a pH of about 8.5, compared with the test strip to the left which is from a 1% glyphosate (450 g/L) solution using town water, which is below a pH of 4.

Figure 2 Adding glyphosate will drop the pH of the tank mix 2 to 3 units depending on initial pH, formulation and rate of glyphosate. The pH after addition of 1% glyphosate (450 g/L) is less than 4 – the yellow test strip. Town water right. Source: AGRONOMO

Figure 2 Adding glyphosate will drop the pH of the tank mix 2 to 3 units depending on initial pH, formulation and rate of glyphosate. The pH after addition of 1% glyphosate (450 g/L) is less than 4 – the yellow test strip. Town water right. Source: AGRONOMO

Recent research in the United States has found drift damage from dicamba continued to be a problem despite the mandating of using XC and UC spray quality. They found one cause was the addition of glyphosate to the mix which reduced the pH of the spray solution (Table 2). Volatilisation of dicamba increases with decreasing pH. Different formulations of dicamba were found to drop the spray solution pH from 7.8 to between 6.5 and 6.9, however the addition of different formulations of glyphosate all dropped the spray solution to 5 or lower.

Table 2 Effect of different formulations of dicamba and glyphosate on spray solution pH. Source: Larry Steckel https://www.farmprogress.com/cotton/spray-ph-becoming-issue-dicamba-applications

Starting pH

of water

Dicamba added

(3 different formulations)

Glyphosate added

(3 different formulations)

7.8

6.9

4.8

7.8

6.5

4.8

7.8

6.7

5.0

Currently the recommendation for dicamba use over the top of dicamba-resistant crops is not to add glyphosate to the mix. This will minimise pH drop and therefore reduce the volatilisation of dicamba and off-target damage to sensitive crops and areas.

Water testing

Knowing the quality of the water you are using is essential for effective pesticide application. Water should be initially tested by a qualified laboratory to establish an accurate baseline for your water quality.

It is important to remember that water quality can vary over time depending on its source. Scheme or town water quality tends to vary very little, however water from surface sources such as dams, tanks and rivers will vary depending on rainfall and other factors. Groundwater can also vary over time depending on how much is being pumped and the recharge rates of the aquifer.

Water should be tested for:

  • pH

  • total hardness

  • bicarbonate (HCO-)

  • salinity (electrical conductivity) or total dissolved salts (TDS)

Test strips can be used to quickly check water quality before and after addition of pesticides and monitor changes in water quality between laboratory tests.

Hand-held meters are available however these will need regular calibration to maintain accuracy.

Where can I get my water tested?

Check with your pesticide reseller or look for accredited laboratories in your state.

High-quality test strips can be purchased online from companies such as Hach - https://au.hach.com/ .

Water testing kits for swimming pools will not be as accurate as those from a scientific supply company.

Further information

GRDC spray water quality – https://grdc.com.au/resources-and-publications/all-publications/factsheets/2014/08/grdc-fs-spraywaterquality

GRDC adjuvants – oils, surfactants and other additives for farm chemicals. https://grdc.com.au/resources-and-publications/all-publications/publications/2018/adjuvants-booklet

Andrew Storrie
Is it safe to plant that next crop? Testing for Damaging Herbicide Residues

With the growing resistance to post emergent herbicides in many weed populations the message going to farmers is that they need to use more pre-emergent herbicides in their farming system.

The problem with pre-emergent herbicides is that they are dependent on activation by soil moisture. Droughts and increasingly variable rainfall patterns can result in insufficient soil moisture to activate the herbicide which leads to poor weed control. The other concern is that herbicides remain active in the soil because they have not been broken down by bacterial activity or hydrolysis.

In many parts of the country, the 2018 winter crop season saw large areas of crop damaged by soil herbicide residues, due to the dry conditions between spraying in 2017 and crop emergence in 2018.

Sulfonylurea residues suppressing chickpea growth (right) compared with plant from area of paddock with no residues. Plants are the same age. Image: AGRONOMO

Sulfonylurea residues suppressing chickpea growth (right) compared with plant from area of paddock with no residues. Plants are the same age. Image: AGRONOMO


The level of herbicide remaining in the soil will be determined by:

  • initial application rate and herbicide type

  • soil pH - most herbicides last longer in alkaline soils while Group B imidazolinones become more water soluble and can move down the soil profile

  • the amount of rainfall received between application and sowing

  • soil temperature - warm, damp soil speeds herbicide breakdown

  • soil texture, that is, the proportion of clay to sand and silt - sandy soils are more likely to have herbicide damage problems than clay soils

  • amount of cultivation - cultivation usually speeds herbicide loss and can dilute it by soil mixing

  • crop type and variety

  • soil organic matter content - high soil organic matter levels reduce the effect of soil active herbicides. However most Australian soils are classed as low in organic matter

  • microbial activity for some herbicides - most of the above factors affect microbial activity

As can be seen from the factors which affect herbicide persistence in the soil, and many of these are out of the farmer’s control.

Most labels will give crop plant back periods based on the amount of rain received since application, soil characteristics and herbicide rate. If you are on the borderline for these characteristics can you safely sow the next crop?

HOW TO DETERMINE IF RESIDUES ARE PRESENT

 1. Susceptible weeds damaged or dying

If there are weeds susceptible to the herbicide present and they show no damage symptoms, it is likely there are no damaging herbicide residues.

However, care must be taken to check whether the particular weeds have not germinated from below or above the possible herbicide band. This prevents weeds absorbing the herbicide.

If it hasn’t rained, you will be none the wiser.

2. Laboratory testing

Laboratory soil testing will cost approximately over $400 per herbicide group and the herbicides to be tested must be specified. The technique most often used is the Gas-Liquid Mass Spectrometer.

Laboratory testing can tell how much herbicide is remaining, but how this relates to crop sensitivity under different conditions can be difficult to interpret.

3. Pot Test (Bioassay)

The simple pot test outlined here does not give an exact measure of the amount of residue present but does indicate whether there is enough herbicide remaining to damage sensitive crops.

The test will take at least 3-4 weeks to perform, so forward planning is essential if sowing and marketing windows are not to be put at risk.

The ‘pot test’ was developed by the late KP Buchholtz for testing of atrazine residues, however it can be used for most soil active herbicides.

1.      Take samples from several locations around the field. Remember that a test is only as good as the sample collected. Sample enough areas to prevent missing any possible high residue areas such as headlands. It may be useful to take separate samples from areas you suspect of being abnormally high. Take samples to the normal cultivation depth, or to 10 cm in non-cultivated fields. It is advisable to take samples from deeper in the profile as well if you have used a highly water-soluble herbicide. If there are any hard pans or restrictions to water flow down the profile also collect soil samples from above these.
See the University of Hertfordshire Pesticide Properties database for the properties of herbicides in question.
Collect about 5 kg per test.

2.      If samples can’t be tested within two weeks of sampling, freeze them. Allowing samples to get hot can reduce the amount of herbicide residue present.

3.      Air dry samples that are wet by spreading out on a tarp. Cloddy soils should be crushed to produce even, pea-sized clods.

4.      Heavy-textured (clay) soils can be improved by adding an equal quantity of clean sand and then mixing thoroughly when dry.

Pot test using oats as the test species to check for Group C (terbuthylazine) and Group D (propyzamide) residues in 2018 after they were applied to a lupin crop in 2017. Very dry conditions in 2017-18 meant there was sufficient herbicide remaining to damage a cereal crop. Left pot has the carbon added. Image: C. Roche

Pot test using oats as the test species to check for Group C (terbuthylazine) and Group D (propyzamide) residues in 2018 after they were applied to a lupin crop in 2017. Very dry conditions in 2017-18 meant there was sufficient herbicide remaining to damage a cereal crop. Left pot has the carbon added. Image: C. Roche

5.      Add the contents of two capsules (0.5 g) of activated carbon (powdered charcoal) to half the soil or sand-soil, mixing thoroughly. The carbon inactivates (binds) the herbicide. Soil treated with carbon should behave in the same manner as soil which contains no herbicide residues. Activated carbon is readily available from pharmacies.

6.      Partially fill two 1-litre containers with soil, but without the carbon and the two containers with the soil-carbon mix. Plant pots or ice cream and drink containers with drainage holes in the base can be used.

7.      Plant about 15 seeds of the crop in question and a known-sensitive species (see Table 1) in each container and cover the seeds with 1-2 cm of soil and lightly water.

8.      Place the containers in a warm place (20-24 degrees C) where they will get plenty of sunlight. Sunlight is necessary for many herbicide symptoms to develop.

9.      Symptoms should appear within 2-4 weeks of planting. Plants in pots exposed to lower temperatures will take longer to show symptoms.

10.   If there are differences in growth between the soil with carbon and soil without carbon pots, it is advisable to only sow crops tolerant of the herbicide in question or go to a fallow.






Trust in science and agriculture under the spotlight

Glyphosate is the world’s most widely used herbicide with approximately 8.6 billion kg used worldwide between 1974 and 2014. This works out to approximately 0.53 kg being used on every cropping hectare each year. Glyphosate resistant crops account for 56% of all glyphosate used (Benbrook 2016). Glyphosate could be said to be the lynch pin of our current farming system.

It is therefore of some concern that recently the Californian Superior Court awarded $AU390 million to a school groundskeeper dying of cancer allegedly through the use of glyphosate. Add to this the fact that Monsanto faces more than 5,000 similar lawsuits across the United States over a range of glyphosate-related claims.

Further south, a Brazilian court recommended the Brazilian health regulation agency (ANVISA) conduct a toxicological review of glyphosate. The court suspended the registration of glyphosate in Brazil until the herbicide has been reviewed. Brazil will be the world’s largest soybean producer in 2018-19 and over 85% of its soybeans are Roundup Ready.

These court cases have also stoked consumer concern about food safety. While the use of glyphosate is not currently under threat in Australia, the Californian and Brazilian court cases mean Australia’s herbicide stewardship must remain world’s best practice.

What’s on offer in the local supermarket.

What’s on offer in the local supermarket.

The outcomes of these two court cases are based on the 2015 International Agency for research on Cancer (IARC) assessment of glyphosate which said that glyphosate is a potential human carcinogen. The IARC looked at the hazard of glyphosate as a cancer-causing agent however it did not consider how the risks are managed when glyphosate is used according to label directions.

The IARC report also found these are also potential human carcinogens:

·        indoor emissions from burning wood

·        high temperature frying

·        some types of shiftwork

·        consumption of red meat

Other agents rated as carcinogenic to humans by IARC include:

·        alcoholic beverages

·        eating processed meat e.g. salami, ham

·        sunlight

·        post menopausal hormone therapy

·        outdoor air pollution

·        the occupation of house painter

·        soot, wood dust

The APVMA supports the use of glyphosate in Australia and it can be used safely according to label directions. Following the 2015 IARC report the APVMA conducted its own glyphosate risk assessment and found there was no reason to place it under formal reconsideration.

A number of other regulators around the world have also conducted assessments of glyphosate. These include:

·        the European Food Safety Authority (EFSA) 2018 – using a risk-based weight of evidence found glyphosate did not cause cancer in humans

·        New Zealand Environmental Protection Agency – found in 2016 that glyphosate was unlikely to cause cancer

·        the US Environmental Protection Agency – found in 2016 that glyphosate was unlikely to cause cancer in humans

·        Health Canada’s Pest Management Regulatory Agency found in 2015 that glyphosate was unlikely to cause cancer

In the largest study of its kind; the US National Cancer Institute conducted the Agricultural health study in Iowa and North Carolina which studied 89,000 farmers and spouses dating back to 1993. Glyphosate was used on 83% of the participant’s farms. The study found no association with solid tumours or lymphoid malignancies including non-Hodgkin’s lymphoma (the cancer of the Californian groundsman awarded damages recently).

What has added to the general public’s concern about glyphosate is California’s Safe drinking water and toxic enforcement act 1986 (Proposition 65) which publishes a list of chemicals known to cause cancer and based on the 2015 IARC report included glyphosate.

Consumer trust

Consumer trust is being tested with multiple stories in the media about these court cases. Many stories are confrontational , often with very little accurate science presented. In fact the general public’s trust in science is seriously under attack by a range of pseudo-scientists out to sell books on their latest theories and ways to stay healthy. The majority of urban residents have little knowledge of where their food comes from or how it is produced. Most consumers have not been trained to analyse information and actually question where stories and information come from.

As an example a group in the US called the Environmental Working Group (EWG) have the motto “Know your environment. Protect your health.” The website is very slick with lots of photos of healthy vibrant people and reviews of a range of topics that affect consumers. Related to the theme of this article is a page under EWG’s Children’s Health Initiative with the heading “Breakfast with a dose of Roundup? – Weed killer in $289 million cancer verdict found in oats cereal and granola bars.”

If that doesn’t get your attention nothing will. The article is well written with a bit of science and quite a bit of emotive language. EWG had sent a range of oat-based breakfast products to a laboratory to be tested for glyphosate residues. Out of the 45 samples from ‘conventional’ agriculture; glyphosate was detected in 43, with 31 samples being above EWGs 0.16 mg/kg stated health benchmark, which by they way no-one else has.

Note that in Australia glyphosate is not registered in oats for pre-harvest application, but is in North America.
A problem with these stories is that you have to do a lot of digging to get down to the facts. I will cover this in another blog later.

Australia must maintain good stewardship

While Australia would have the best pesticide regulatory system in the world this is no time for complacency. We must use world’s best stewardship practice with all pesticides. It is essential that advisers and growers follow labels and permits closely as many all our trading partners are often looking for non-tariff barriers to trade. For example China has no maximum residue limit level set for many grains they import so can immediately set an allowable MRL if they want to reduce imports or negotiate on price.

Australian grain industry body Grain Trade Australia has strict codes of practice which growers and advisers should carefully follow.

Most grain buyers are also bringing in stricter monitoring of grain quality and can trace back to individual loads. New technology also allows the testing of samples at the grain receivals point. The importance of this issue is reflected in CBH in Western Australia introducing a 3-strikes policy regarding the delivery of contaminated grain as a warning that they are serious about grain quality.

Glyphosate is registered for use as a pre-harvest emergent herbicide on wheat, canola, chickpeas, lentils, field peas and faba beans, and has an emergency permit (Permit PER82594) for use on feed and food barley, but not malt barley. 

Pre harvest spraying can help reduce weed seed set and enable even ripening of the crop. However application of pesticides close to harvest increases the risk of unacceptable levels of residues being detected in grain.

A management problem with applying pesticides at this time is the grower determining whether the crop is at the right stage. For example when glyphosate is applied to barley the maximum moisture content is 27% (late dough), with a minimum 5 day harvest withholding. Determining 27% moisture takes a bit of effort and the crop can be greener than you would think as shown in the image below. Subsequently applications are then often delayed due to a miscalculation of the acceptable stage or spraying logistics which in turn increases the risk of unacceptable grain residues. On the other hand applying glyphosate too early can affect grain quality and yield.

Top row of barley at 27% -the correct time for glyphosate while the bottom row are 34%, which is too early. Image: Craig Brown

Top row of barley at 27% -the correct time for glyphosate while the bottom row are 34%, which is too early. Image: Craig Brown

Therefore it is my personal opinion that the late use of glyphosate in crops should be reviewed and alternative weed management strategies be investigated and promoted.

Andrew Storrie
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

Dicotyledons:

  • 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)

Clays

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

Facebook

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