BBBeeesssttt MMMaaannnaaagggeeemmmeeennnttt PPPrrraaaccctttiiiccceeesss fffooorrr

DDDrrryyylllaaannnddd CCCrrroooppppppiiinnnggg SSSyyysssttteeemmmsss

Great Brome (Bromus diandrus)

Great brome (Bromus diandrus) is an annual grass weed widely distributed across southern Australia. It can cause enormous problems for landholders across the mid and lower Murrumbidgee catchment. A population of 100 plants/m2 causes an average yield loss of 30% in wheat crops due to its high level of competitiveness for water, nutrients and space (Gill, Poole & Holmes 1987). The seeds can contaminate wool and injure livestock through penetration of eyes, mouths, feet and intestines. It also hosts a range of cereal diseases. (Figures 1 & 2)

Photo: Sheldon Navie

Figure 2. Bromus diandrus infestation

Legislation

Great brome is not declared noxious in the Murrumbidgee catchment under the Noxious Weeds Act 1993.

Taxonomy

Great brome is the accepted common name for Bromus diandrus but it is also known as ripgut brome, ripgut grass, giant brome, slands grass, jabbers and Kingston grass.

Bromus diandrus is one of 130 species in the Bromus L. genus, all of which are simply known as brome grass. Bromus rigidus is another common species in Australia. Its accepted common name is rigid brome Photo: Sheldon Navie but it may also be known as ripgut brome, brome grass and even great brome. Figure 1. Bromus diandrus inflorescence

Origin and Introduction KEY POINTS Great brome is native to the Mediterranean region of • Great brome is an increasing problem in the Turkey, Cyprus, Egypt and Iraq but now infests other Murrumbidgee catchment and should not be Mediterranean areas of Europe, Africa, Britain, North overlooked. America, South Africa, Australia, New Zealand, South

• New herbicides are available for control of Korea, Japan and Russia. great brome in wheat. Great brome was introduced into Australia around • Aim for 2 consecutive years of weed control 1875 as a contaminant of crop seeds, forages and to deplete the weed seed-bank. wool, attached to livestock or in ship ballasts (Cooper & Moekerk 2000).

Distribution • the easy removal of other grass weeds has allowed great brome to proliferate

Great brome quickly became naturalized across southern • the adoption of minimum and no-till farming systems Australia due to its aggressive nature and pre-adaptation has caused an increase in great brome populations to Australia’s temperate climate. It is distributed from south-east Queensland to south-west Western Australia • sheep numbers in the Murrumbidgee catchment (Figure 3). It is adapted to a range of climatic conditions have declined allowing annual grasses including great and soil types from acidic to alkaline and sandy to loamy. brome to set seed freely; and It is found in crops, pastures, fallows, roadsides, • the overall area cropped in the Murrumbidgee wastelands, national parks and reserves and coastal sand catchment has increased. dunes.

Identification

Great brome leaves are rough, hairy, dull and often have visible purple stripes along the leaf veins. The leaf sheath is tubular, the ligule is prominent and membranous, and the stems are hairy (Figure 4). The inflorescence is a loose, nodding panicle with long stalked spikelets (Figure 5).

Figure 3. Estimated distribution of great brome in Australia (Kon & Blacklow 1995).

Biology and Ecology

Great brome is a major weed in the Murrumbidgee catchment because:

• it is among the most competitive of all grass weeds and Photo: Sheldon Navie small populations in a wheat crop can cause large yield losses Figure 4. Bromus diandrus stem

• it effectively competes with crop plants for nitrogen and phosphorous

• each plant can produce more than 3000 seeds

• the seeds contaminate grain, wool, animal skins and meat, and injure livestock by penetrating skin, eyes, feet and intestines

• the plant hosts a number of cereal diseases including take-all (Gaeumannomyces graminis), ergot (Claviceps purpurea) and cereal cyst nematode (Heterodera avenai), all of which can cause significant losses in cereal crops

• the plant sheds a large proportion of seed before harvest

• it is drought tolerant

Photo: Sheldon Navie • it has a higher tolerance of phosphorous deficiency and better responsiveness to added nitrogen than wheat Figure 5. Bromus diandrus inflorescence

• few management tools are available for great brome All Bromus species appear very similar in the seedling control in cereals and vegetative stages. Great brome seedlings can be • there is a poor understanding of the ecology and confused with wild oats as they both possess hairs on population dynamics of great brome their leaves and stems. (Table 1)

Table 1. Distinguishing characteristics of Bromus diandrus (Cooper & Moerkerk 2000; Kon & Blacklow 1988).

Bromus diandrus Height 30-90cm Leaves 10mm wide, stout, erect, long/dense hairs Ligule Prominent, membranous Panicle Loose and nodding,150-200mm long Spikelet branches Longer than spikelets, sometimes exceeding 20mm Awn length 35-55mm Abscission scar Circular Lemma callus Short (≤1mm), spherical with rounded tip Chromosome number 2n=56

Seed dormancy and germination The hot, dry conditions found at the soil surface are unfavourable for germination and this could be the Great brome seeds are inherently dormant at seed shed. underlying reason great brome has increased under They remain dormant in high temperatures over summer no-till systems. Seeds lie dormant on the soil surface but regain germinability when conditions become until being buried at sowing, placing them in a favourable. Most seeds will germinate after rain the favourable environment for germination thus following autumn as rainfall is the biggest determinant of promoting in-crop emergence. germination (Figure 5). Those which don’t can remain viable in the soil for up to 2 years, less if exposed to a Seeds will germinate over a range of temperatures but humid environment and more on non-wetting soils. the optimum is 20°C.

100

Emergence (%) 80 60

40

20

0 M A MJ J ASON Month

Figure 5. Emergence pattern of great brome over time.

Seedling establishment to the soil surface until culm elongation in spring (Figure 6). Seedling establishment is rapid and uniform and it takes only 2 days to complete 50% emergence. However The efficient fibrous rooting system helps plants establishment can be protracted due to emergence from survive periods of moisture stress. It is concentrated in varying soil depths (ideal depth is 1cm) or dormancy the top 15cm of the soil profile. enforced by the seed remaining on the soil surface. Establishment is more rapid and uniform under wheat stubble than bare soil as the wheat stubble microenvironment accelerates release from dormancy.

Great brome plants can produce many tillers (>50) when plant density is low and nutrient status is high. It has a prostrate growth habit with tillers being strongly oppressed

Seed production and dispersal

Great brome produces up to 3380 seeds per plant but this is highly variable (Kon & Blacklow 1995). Seed shed occurs 26 days after anthesis. Seeds are dispersed by wind, animals, machines, clothes and as crop seed contaminants. (Figure 7)

Figure 7. Bromus diandrus seed (Wilding, Barnett & Amor 1998)

Management

Despite the major impact great brome has on farming systems in southern Australia, it is a manageable weed. The development and implementation of a clear and well defined integrated weed management (IWM) plan is vital to achieve effective control and delay the development of herbicide resistance. The plan should include cultural, biological and chemical techniques Photo: Sheldon Navie from across the tactic groups listed below (Table 2):

Figure 6. Bromus diandrus showing prostrate growth habit 1) Deplete the weed seed-bank 2) Kill existing weeds Flowering 3) Prevent seed set 4) Prevent seeds entering seed-bank Great brome flowers after vernalisation (low 5) Prevent introduction from external sources. temperatures) or short photoperiods followed by long photoperiods. Populations vary in time to flowering in response to the growing season length. Flowering can occur any time between August and November.

Table 2. The tactic groups, techniques and their effectiveness for great brome management (Bowcher, Gill & Moore 2005).

Tactic Likely Control Control Range Tactic Group (%) (%) 1 Burning residues 70 60-80 1 Autumn tickle 50 20-60 1 Delayed sowing 70 30-90 2 Knockdown (non-selective herbicide) 80 30-99 2 Pre-emergent herbicide 80 40-90 2 Post-emergent (selective) 90 75-99 3 Pasture spray-topping 75 50-90 3 Silage and hay 60 40-80 3 Grazing 50 20-80

4 Residue collection at harvest 40 10-75

An integral component of the great brome IWM plan and Group A herbicides can be used followed by should be a robust crop rotation ensuring at least 2 Clearfield® wheat where the Midas® herbicide can be consecutive years of great brome control. For example, a used. Pastures may be substituted for canola in lower break crop such as lupins or canola where the triazines rainfall areas where grazing and spray-topping may be available Clearfield® varieties and the cost of Midas® used. ($36/ha). Monza™ and Atlantis® also only give suppression rather than complete control. Chemical Options A trial conducted in 2003 at Mannum, South Australia, Until recently, there were very few herbicide options for to evaluate the efficacy of different herbicides for great great brome control in cereal crops. The following 3 brome control showed Midas® alone or in a mix with hebicides (all Group B) are now registered: trifluralin to be the most effective treatment (Table 3) (Kleemann & Gill 2003a). An equivalent trial 1. Midas® (MCPA/imazapic/imazapyr) for use in Clearfield conducted in the same year at Warooka on the Yorke wheat varieties only (CLF Janz and CLF Stiletto) Peninsula of South Australia (without the metribuzin 2. Monza™ (Sulfosulfuron) treatments) showed similar results with Midas® at 3. Atlantis® (Mesosulfuron-methyl). 900ml/ha the most effective treatment followed by Midas® 900ml/ha + trifluralin 1.2L/ha (Kleemann & Gill Limitations imposed by these herbicides include plant 2003b). back restrictions (especially in low rainfall areas), few

Table 3. Effect of pre and post emergent herbicide treatments on great brome in Clearfield Janz wheat at Mannum in 2003 (Kleemann & Gill 2003).

Treatment Brome seed Rank Chemical Brome production % Control (1 best, cost ($/ha) plants/m2 (seeds/m2) 10 worst) Control (no herbicide) 0 45 393 0 10 Pre-emergent Metribuzin 200g/ha (IBS) 15 30 674 33 8 Metribuzin 200g/ha + Trifluralin 23 20 634 56 4 1.2L/ha (IBS) Trifluralin 1.2L/ha (IBS) 8 41 414 9 9 Post-emergent Midas® 900ml/ha 36 6 13 87 1 Atlantis® 330ml/ha 26 21 118 53 5 Monza™ 25g/ha 28 25 33 44 7 Midas® 900ml/ha + Trifluralin 44 7 26 84 2 1.2L/ha (IBS) Atlantis® 330ml/ha + Trifluralin 34 23 139 49 6 1.2L/ha (IBS) Monza™ 25g/ha + Trifluralin 36 17 82 62 3 1.2L/ha (IBS)

Metribuzin (Lexone® or Sencor®), a group C herbicide, economically viable alternative to using the is currently being investigated for the control of great Clearfield® system and Group B herbicides. brome in barley. Trial results have shown that tank- mixes of metribuzin with trifluralin (Treflan®) A wider range of herbicide options is available for incorporated by sowing (IBS) or pendimethalin great brome control in break crops such as lupins, (Stomp®) provide excellent control of great brome and canola and field peas. The triazines and Group A is safe on the crop (Kleemann & Gill 2004). However herbicides are very effective however Group A performance of metribuzin can be inconsistent, herbicides carry a high risk of developing herbicide particularly when applied under dry sowing conditions resistance. and on non-wetting sands. This is because the herbicide is highly soluble and requires a moist seed-bed for ▪ Resistance note: Great brome populations activation. When using metribuzin, be aware of the risks resistant to Group A ‘fop’ herbicides (Targa® and of herbicide movement with rainfall, especially in press Verdict™) have been recorded in Victoria and a wheel furrows where it can cause severe crop damage. population resistant to the Group B herbicide Crop phytotoxicity can also occur on soils of low clay Monza™ has been identified in Western Australia content or low organic matter. (P. Boutsalis pers comm.). There is a potential threat of resistance developing to Group A, Group B Metribuzin tolerance varies among wheat cultivars. The (sulfonylureas and imidazolinones) and Group C recent release of EGA Eagle Rock, a wheat variety from (triazines and substituted ureas) herbicides in the Western Australia bred for tolerance to metribuzin, has Murrumbidgee catchment as this has already been hard quality attributes and potentially provides an reported interstate and overseas.

Local demonstration

Local demonstration sites were established in 2006 and great brome (Bromus diandrus), wild oats (Avena 2007 to show the efficacy of post-emergent herbicides for fatua) and barley grass (Hordeum leporinum). the control of great brome in wheat.

Aim

To compare the efficacy of 3 post-emergent herbicides for the control of great brome in wheat.

Methodology

The 2006 demonstration site was located approximately 20km north of Narrandera, NSW. In 2004 the paddock was sown to wheat and in 2005 was sown to oats. The oat stubble was burnt prior to sowing to Clearfield® Janz wheat on 21st June, 2006.

The 2007 demonstration site was located approximately Photo: Cynthia Griffiths 5km south of Ardlethan, NSW. The paddock was sown to wheat in June 2007 and the dominant weeds present were The 2007 demonstration site at the time of treatment application (02/07/07).

The treatments applied and their approximate cost per hectare were:

Treatment Cost ($/ha) 1 Control (no herbicide) 0 2 Midas® (900ml/ha) + Hasten (500ml/100L) 52.72 3 Monza™ (25g/ha) + DC Trate (2000ml/100L) 32.46 4 Atlantis® (330ml/ha) + Hasten (1000ml/100L) 34.34

The treatments were applied on 04/08/06 and application was Z13-Z22 (3 leaf-2 tillers) and the 02/07/07using a 15L back pack sprayer, flat fan nozzles great brome growth stage at application was also and 3 bar of pressure. A water rate of 133L/ha (106L/ha Z13-Z22 (3 leaf-2 tillers). In 2007 the great brome in 2007) was used. In 2006 the crop growth stage at was Z13-15 (3-5 leaf) at the time of spraying.

Results and Discussion (2006) 2006 and 100% in 2007. This was followed by Atlantis which gave 28% control in 2006 and 61% Midas was the most effective treatments in both years control in 2007 and then Monza which gave only 9% providing 65% reduction in the great brome population in control in 2006 and 11% control in 2007.

2006 2007 Average Plants/m2 Plants/m2 Treatment Plants/m2 Plants/m2 Prior to % Control Prior to % Control % Control 28 DAT 28 DAT treatment treatment Control 25 25 0 32 32 0 0 Midas 11 4 65 64 0 100 83 Monza 35 34 9 44 39 11 10 Atlantis 27 19 28 112 44 61 45

120

100 100

83 80 65 61 2006 60 2007 45 Average Control (%) 40 28

20 9 11 10 0 0 0 0 Control Midas (900mL/ha) Monza (25g/ha) + Atlantis + Hasten DC Trate (330mL/ha) + Hasten Treatment

At 28 DAT, Midas® had severely stunted and discoloured all plants. This went on to result in a high percentage of plant deaths.In 2006, the larger plants looked to be less affected than the younger plants indicating that the herbicide may have been applied too late.

Atlantis® stunted and discoloured the great brome plants however again, in 2006 the larger plants appeared to be less affected. Atlantis may have shown poor results due to some of the great brome plants being outside the recommended growth stage for application which is Z11- Z21 (1 leaf-1 tiller). Atlantis also resulted in initial transient crop yellowing however this was not noticeable 28 DAT.

Monza™ didn’t significantly affect the great brome plants Photo: Cynthia Griffiths with the only symptoms being slight stunting of the smaller The Control plot 56 DAT (27/08/07) (plot 3) plants. In 2006 Monza™ also may have performed poorly due to some great brome plants being outside the recommended growth stage for application. Best results are obtained when great brome is at growth stage Z11-Z13 (1-3 leaf) however they were up to Z22 (2 tillers) when the herbicide was applied. Sufficient rainfall to wet to 5-7.5cm within 7-10 days of application, which did not occur, also aids efficacy.

Although Monza™ and Atlantis® gave low levels of plant death the remaining plants were severely stunted and discoloured. Their competitive ability is likely to be low compared to the control plots but they will probably set seed at maturity and have a negative impact on the weed seed bank. Photo: Cynthia Griffiths

The Midas® treatment 56 DAT (27/08/07) (plot 7).

Economic Analyses

No harvest data was recorded due to the drought therefore actual economic analyses using yield data and treatment cost to determine the most beneficial treatment cannot be done. However, calculations using the current 2006-2007 ASW National Pool price of $380/tonne (GST exclusive) (Source: AWB Limited) and the price of Midas® ($52.72/ha) and Atlantis® ($34.34/ha) shows that the Midas® treated plot only needs to yield 48.37kg/ha (0.04837t/ha) more than the Atlantis® treated plot to recover the additional cost of the herbicide. In addition to the economic benefit or loss, other factors need to be

Photo: Cynthia Griffiths considered such as weed survivors setting seed and

increasing the weed seed bank and contamination of The Atlantis® treatment 56 DAT (27/08/07) (plot 12). wheat with weed seeds at harvest.

To evaluate the economic benefit of different herbicides you need to consider the weed population, percent control achieved, potential wheat yield, yield loss, actual yield and cost of the herbicide. An example of how to estimate your gross margin (looking at weed control only) is given below.

Photo: Cynthia Griffiths

The Monza™ treatment 56 DAT (27/08/07) (plot 1).

Example gross margin for the treatments and control achieved here assuming a starting great brome population of 100 plants/m2, a wheat yield loss of 30% at a great brome population of 100 plants/m2 (Gill et al. 1987), a potential wheat yield of 4t/ha and a wheat price of $200/t.

Great brome Actual Gross margin % Yield Income Herbicide cost Treatment % Control population yield ($/ha) (weed loss ($/ha) ($/ha) (plants/m2) (t/ha) control only) Control 0 100 30 2.8 560 0 560 Midas® 65 35 10.5 3.58 716 50.40 665.60 Atlantis® 28 72 21.6 3.136 627.20 30.36 596.84 Monza™ 9 91 27.3 2.908 581.60 29.50 552.10

From the gross margin, we can see that Midas® gives the Conclusion highest return per hectare despite being the most expensive of the three herbicides as it provides the Midas® provided the best control of great brome in highest level of weed control. When deciding on herbicide wheat when compared to Monza™ and Atlantis® in options, other factors such as crop tolerance, plant back both years the demonstration was run. However, it is periods, withholding periods, other weed species present, significantly more expensive than the other two damage to non-target species (environmental damage), herbicides so the economic benefit needs to be herbicide use history (resistance risk) and performance of evaluated before making herbicide choices. the Clearfield® varieties compared to conventional varieties also need to be considered.

Cultural Options Cultivation Crop choice and rotation Cultivation can be used to stimulate pre-sowing Aim to control great brome in the year/s before the cereal germinations of great brome that can be controlled crop as control is best in pulses, then pasture and then with knockdown herbicides. wheat. Grazing Herbicide tolerant crops Great brome is only palatable in the vegetative stage The Clearfield® system uses wheat cultivars tolerant to so grazing is a poor management tool. the Midas® herbicide and is the most effective in-crop control option for wheat. Biological Options

Triazine tolerant canola allows the use of triazine Pathogenic fungi, viruses and nematodes are all herbicides which give good control of great brome. natural enemies of great brome however many of these also attack cereals and are therefore unsuitable Competitive crop and pasture species for use as biological control agents. Strains with a narrow host range do exist and could potentially be Barley is a more competitive species than wheat and used as a control option in the future. suffers a lower yield penalty from great brome infestations. References

Seeding rate and row spacing Bowcher, A., Gill, G. & Moore, J. (2005) ‘Brome grass’ in Integrated Weed Management in Australian Cropping Systems (forthcoming), Higher seeding rates and narrow row spacings that result Cooperative Research Centre for Australian Weed Management 2 (Weeds CRC). in a higher number of crop plants/m can suppress great brome and reduce seed set. Cooper, J. & Moekerk, M. (2000) ‘Bromus diandrus/ Bromus rigidus’ in Weed ID/ Management, http://www.weedman.horsham.net.au. Fertiliser placement Gill, G.S., Poole, M.L. & Holmes, J.E. (1987) Competition between Banding fertiliser under the wheat rows at sowing enables wheat and brome grass in Western Australia, Australian Journal of the wheat seedlings to access the nutrients before the Experimental Agriculture vol. 27, pp. 291-294. weed seedlings. This can result in a lower yield loss than Kleemann, S. & Gill, G. (2003a) Management strategies for the broadcast applications. Furthermore, broadcast control of brome grass, GRDC project UA00060, University of applications of nitrogen have been shown to stimulate in- Adelaide. crop great brome germination (Rainbow & Slee 2004). Kleemann, S. & Gill, G. (2003b) Herbicide options for the control of brome grass in wheat and barley, GRDC project UA00060, Disease and insect control University of Adelaide.

Disease and insect free crops are more competitive Kleemann & Gill (2004) Herbicides for the control of Brome grass in wheat and barley, GRDC project UA00060, University of Adelaide. against weeds than stressed crops. Kon, K.F. & Blacklow, W.M. (1995) The Biology of Australian Delayed seeding Weeds, Vol. 1, ed. R.H. Groves, R.C.H. Shepherd & R.G. Richardson, R.G. & F.J. Richardson, Melbourne.

Delayed seeding allows greater weed kill with knockdown Rainbow, R.W. & Slee, D.V. (2004) The essential guide to no-till herbicides prior to sowing. farming. South Australian No-Till Farmers Association publication.

Controlled traffic Wilding, J.L., Barnett, A.G. & Amor, R.L. (1998) Crop Weeds, R.G. and F.J. Richardson, Melbourne.

Controlled traffic systems allow optimal timing of herbicide Yu, Q., Cairns, A. & Powles, S.B. (2004) Paraquat resistance in a applications and better soil conditions for crop growth. population of Lolium rigidum. Functional Plant Biology, Vol. 31, pp 247-254.

Further Information: www.murrumbidgee.cma.nsw.gov.au or www.dpi.nsw.gov.au

Disclaimer

The information contained in this publication is based on knowledge and understanding at the time of writing (2008). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of New South Wales Department of Primary Industries/Murrumbidgee Catchment Management Authority or the user’s independent adviser.

The product trade names in this publication are supplied on the understanding that no preference between equivalent products is intended and that the inclusion of a product name does not imply endorsement by NSW Department of Primary Industries or Murrumbidgee CMA over any equivalent product from another manufacturer.

ALWAYS READ THE LABEL Users of agricultural chemical products must always read the label and any Permit, before using the product, and strictly comply with directions on the label and the conditions of any Permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or omitted to be made in this publication.

This project has been funded through the Australian and NSW Governments’ National Action Plan for Salinity and Water Quality.