Section 8: Profiles of common weeds of cropping
8.1 Weed identification
Wild oat ligule.
Note the absence of auricles.
Easily confused with brome grasses.
(Photo A. Storrie)
Correct weed identification is critical to the selection of appropriate control tactics. Below is information to assist with identification including links to resources and links to information on specific problem weeds in cropping.
8.1.1 Collecting and submitting plant samples for identification
If taking weed samples to assist with identification, a few basic collection principles need to be observed:
Submit fresh samples – collect as close to the time of identification as possible and store in a plastic bag in the refrigerator. If practical, an alternative is to plant the weed in a pot. When collecting and transporting weeds, ensure that the plant and any accompanying soil are contained so there is no risk of spreading the weed.
Dried specimens can be submitted, however they need to be carefully pressed and cured before sending. Flower colour must be noted, as often the colour fades with drying.
Submit as much of the plant as possible, especially reproductive parts, but also including the underground parts. Dig up the plant and gently shake off the loose soil surrounding the root system. Carefully washing the roots is also helpful but take care, as the original seed (point of germination) may still be attached and could assist identification.
Provide flowers, seeds or fruit - these are the most distinctive features for identification. Failure to provide reproductive parts may prevent successful identification.
If a range of plant health or growth stages are present, it is advisable to provide representative plants from each.
A handy form to provide the following important information can be found here:
- name, address and contact details
- the situation in which the plant is growing, including location, soil type and distribution (e.g. scattered, clumps, single) – NOTE: this information is VERY important in aiding the identification of weeds.
- any information that may assist with identification:
- Is the weed growing where imported fodder has been fed out?
- Have particular weed management tactics been used in the current season?
- When did you first notice the weed?
8.1.2 Digital photos can be useful for weed identification
Good quality images can be emailed to an expert, however remember to include the information listed above.
Features important for identification are:
- the whole plant, showing architecture: is it prostrate, erect, a bush, a vine etc? Include an object such as a coin or ruler to indicate size
- the key parts of the plant including:
- leaf shape and colour
- flowers, fruit, seeds – REMEMBER without these reproductive parts identification is often impossible
- underground parts such as bulbs and tubers
When taking digital photos be sure that the weed can be distinguished from the background (e.g. other plants, soil) by using a plain background such as a sheet of paper, cloth or a car bonnet.
Ensure that shadows do not obliterate the weed, especially its key features. Fill-in flash can be useful, but do not over-expose (wash-out) the images. Under-exposed images (darker) are often more useful than over exposed images.
Use the macro setting when taking close-ups of important features, such as flowers and leaf surfaces.
Check that the photos are in-focus and not blurry by blowing them up on the camera LCD screen. If out-of-focus, delete the images and try again. Steady camera by bracing against something or use a tripod.
8.2 Weed identification resources
Sweet summer grass infesting grain sorghum.
(Photo V. Osten)
GRDC Weeds Ute Guide application
GRDC’s popular Weeds Ute Guide is now available for your iPhone or android smart phone. Weed ID helps you identify the most common annual, biennial, and perennial weeds in the southern and western grains regions of Australia
Weed identification & information
Information on weeds by state - Not all crop weeds covered, but some useful pictures and information on those that are. (Weeds Australia)
Department of Primary Industries NSW weed profiles
Mainly environmental and rangeland weeds, but some weeds of cropping are included with good pictures and management information. (NSW DPI)
WEEDpak - weed identification and information guide
WEEDpak - Weed identification and information guide - compiled to assist with the identification and management of common weeds of cotton. Colour photographs including weed growth stages are available for each weed. Weed biology and ecology information is also provided.(Cotton Catchment Communities CRC Website)
WA Herbarium - http://florabase.dec.wa.gov.au/
Sydney Royal Botanic Gardens Herbarium – PlantNET http://plantnet.rbgsyd.nsw.gov.au/search/simple.htm
Western Weeds: http://wswa.org.au/western_weeds.htm#contents
8.3 Profiles of common weeds of cropping
Click on the weed name below to be taken to further information on this weed.
Annual ryegrass (Lolium rigidum )
Barley grass (Hordeum spp.)
Barnyard grasses (Echinochloa spp.)
Black bindweed (Fallopia convolvulus)
Bladder ketmia (Hibiscus trionum)
Brome grass (Bromus spp.)
Capeweed (Arctotheca calendula)
Doublegee (Emex australis)
Feathertop Rhodes grass (Chloris virgata)
Fleabane (Conyza spp.)
Fumitory (Fumaria spp.)
Indian hedge mustard (Sysimbrium orientale)
Liverseed grass (Urochloa panicoides)
Muskweed (Myagrum perfoliatum)
Paradoxa grass (Phalaris paradoxa)
Silver grass (Vulpia spp.)
Sweet summer grass (Brachiaria ericuformis)
Turnip weed (Rapistrum rugosum)
Wild oats (Avena fatua and Avena ludoviciana)
Wild radish (Raphanus raphanistrum)
Windmill grass (Chloris truncata)
Wire weed (Polygonum aviculare and Polygonum arenastrum)
8.4 Further information
Part 6 of the Integrated Weed Management Manual: Weeds