A tufted, annual, softly hairy grass, up to 900 mm tall, with a drooping seed head and stiff awned seed that contaminates wool.
Description
Cotyledons:
One.
First leaves:
Sometimes tinged with purple or red. Broad.
Leaves:
Leaves rolled in the shoot.
Blade - 80-400 mm long, 5-20 mm wide. Parallel veins. Hairy. Rough. Flat or loosely folded.
Ligule - Membranous, more than 2mm long.
Auricles - None.
Collar - Prominent and a lighter colour.
Sheath - Tubular. Hairy. Often red to purple striped, especially near the base.
65 has stomatal patterns for leaves.
Stems:
100-800 mm tall. Hairy. Erect, round and hollow with solid nodes. Droop with weight of the seed.
Flower head:
Panicle. 80-250 mm long. Erect when young but opens out and hangs to one side as it matures.
Flowers:
Spikelets - 60-100 mm long including the awn. 4-10 flowered. Seed spikelets on long slender stalks that nod to one side of the stem. Initially purplish fading to pale yellow. Persistent.
Glumes - Hairless. Outer ones awnless. Inner outer glume 15-25 mm long, upper one 20-30 mm. Palea - Lemma - 20-30 mm long without the awn. Lanceolate. Rough to touch. 7 prominent veins. Awn - 35-60 mm long. Rough to touch. Stamens - Anthers -
Fruit:
Seeds:
1-2 mm wide, 20-30 mm long with a 20-50 mm rough bristle. Seed weight is 0.01-0.015 g/seed (66).
In pure stands seed production is fairly constant over the range of 100-1000 plants/m2 (67).
Seed production is 631-3380 per plant for B. diandrus and 1156-2908 per plant for B. rigidus (68). Overseas data indicates more realistic field seed productions at 15-60 seeds/plant for B. diandrus growing in a cereal crop (69, 66).
Roots:
Large fibrous root system.
Bromus diandrus roots occur mainly in the top 10 cm of soil (67).
Key Characters:
70 has a key for 23 species of Bromus.
B. diandrus, B. rigidus and B. sterilis are considered varieties of one species by 71.
Biology
Plant weight is 0.4-0.85 g vegetative plus 0.35-1 g DW seed per plant at maturity growing in a cereal crop (66).
The basic chromosome number of 7, B. sterilis, B. tectorum and B. scoparius are diploid, B. madritensis, B. rubens and B. hordeaceus tetraploid, B. rigidus hexaploid, and B. diandrus octoploid (65).
Bromus diandrus is octoploid (2n=56) and Bromus rigidus is hexaploid (2n=42). They form polyploid complexes (72, 73, 68) .
B. diandrus is self compatible, and inbreeding with less than 1% out crossing (74).
Life cycle:
Annual grass. Germinates with autumn rains in about 2 days and produces about 1 leaf per week. It starts tillering at 4 weeks, forms the first node at 12-13 weeks and the seed head emerges a week or two later in late winter/spring.
(Freshly harvested seed takes 34-59 days to emerge in moist conditions (75))
Physiology:
Relatively drought tolerant (76).
Very sensitive to salt spray (77) and not found close to the coast and does not tolerate partial burial by sand (78).
Leaf production occurs for 14 weeks and 10-11 leaves are produced, tillering starts after the second or third leaf is formed, panicles appear in the fifteenth week, growth stops at 0 deg C when the plants are less than 6 weeks old and at 6 deg C for older plants in Spain (79).
In WA, the time from germination to panicle emergence depended on the length of the growing season where the seed was collected (80).
Vernalisation reduced the time from germination to flowering from 54 days to 17 days in Oregon (81).
Grows relatively independently of temperature according to 82 but 83 found a good temperature relationship where it took 325-340 degree days to produce 3 leaves in two field sites of differing average temperatures and rainfalls.
B. diandrus RGR similar to wild oats and lower than B. mollis and B. multiflorum (84).
Grows well in partial shade (85).
Tolerant to acid rain (86).
Reproduction:
Flowering times:
September to November in Perth.
September to November mainly in South Australia.
Plants under water stress flower earlier (76).
B diandrus flowers later than B. rigidus (68).
Seed Biology and Germination:
Non dormant seed germinates with 40 hours of wetting at 20 deg C (80) and 95% of seed of B. diandrus will germinate within 27 days of shedding (87).
Prefers to germinate in dark conditions. Germination is often stimulated by cultivation that buries the seed. After ripening period is 7 days at 10 deg C and increasing to 60 days at 25-30 deg C (88). Shallow burial reduces the after ripening period (89).
After ripening period is satisfied by the end of summer but not all seed germinates with the break indicating a small induced dormancy in SA (90, 91). After ripening protects Bromus diandrus from false breaks (92). Bromus diandrus loses dormancy faster than Bromus rigidus (93).
Plants grown under water stress produce more dormant seed (76).
A short awned variety of B. rigidus from Geraldton is reported to have 30% innate dormancy (68).
B. diandrus seed that is dormant due to environmental conditions is viable for at least 2 years (87).
Dormant seed germinates in response to gibberellic acid, removal of palea and lemma or water leaching of seed (80).
Germination levels increase with time after seed set. In WA, 12%, 30% and 50% of seed was able to germinate in December, February and April respectively (probably on B. rigidus?) (Zaicou, 1994). 75 reports no dormancy in Australian B. diandrus 3 months after harvest but some dormancy in B. rigidus which was lost with time in storage. Temperature
Optimum germination conditions are alternating temperatures around 10/15 deg C on a 12 hour cycle (22).
Germination in at autumn temperatures of 10/20 deg C was 56-95% in light and 95-99% in dark (91).
At 10-25 0C, around 90% of seed will germinate and only 20% at 30 0C (Gill and Blacklow, 1985). Soil temperatures vary from 21-43 0C in WA paddocks in March (Zaicou, 1994). High and fluctuating temperatures were not required to break dormancy and may sightly increase the after ripening period (92).
Temperature but not day length had a big effect on germination (94).
95 has germination by temperatures over the 0-40 deg C range.
The main flush of germination usually occurs with the first two rains of the season. In field trials, 25% of the seed bank emerged on the first rain, 20% on the second and less than 5% on the third. These figures could be almost doubled by hand watering the site (Zaicou, 1994). Thus, control of seed set for two years is required under field conditions to reduce brome to uneconomic levels.
96 found little reaction to smoked water as nearly all the seed germinated regardless of treatment.
After ripening period is less under stubble than on bare soil (91).
Germination tends to be restricted to a fairly short period in autumn after the opening rains with little germination until the following autumn (91). Burial
Depth of burial had little effect on longevity of non dormant seed, but on dormant seed longevity was least at 1 cm and greatest at 15 cm burial depths (97).
No B. diandrus seed germinated after 6 months burial at 5 or 15 cm and seedling establishment was greatest when buried 5 cm with 97% emergence within a month and less than 1% emergence from 15 cm. Establishment of surface sown seed occurred over and 18 month period (87).
90 days after burial at 0.5 cm, 7cm and 20 cm in dry soil, seed had a viability of 47%, <4% and 20% respectively and in moist soil was <4% for all depths. By 150 days after burial seed all depth by moisture treatments had a viability of <2% (98).
Vegetative Propagules:
None.
Hybrids:
Little evidence for hybrids between B. diandrus and B. rigidus (74), but polyploidy is common.
Bromus diandrus and B. rigidus had identical zymograms, providing support for their conspecific recognition (99).
Allelopathy:
Leachate from the litter of the understorey sp. Pholistoma auritum inhibited the growth of B. diandrus and wild oats (Avena fatua) ()100.
Population Dynamics and Dispersal.
Seed is dispersed mainly as a contaminant of crop seed and by attachment to animals.
Great Brome (B. diandrus) tends to occur around the outsides of cropped areas and along fence lines whilst B. rigidus tends to occur within the cropped area.
Management of the seed reserves should be a priority in infested areas (101, 102).
103 have done some modelling on spread.
Over a 2 year period B. diandrus had 88-100% establishment and produced 15-35 seeds per plant in the field (69) which is similar to 66 30-60 seeds/plant and much lower than the 68 values of 631-3380 seeds/plant from southern Australia. Competition
Fast growing with high relative growth rates (104).
Increasing planting rates of wheat and barley linearly increased yield and reduced brome grass seed production (105).
Similar to slightly less competitive to wild oats (106, 107, 108). 109 found a good relation between brome seedling numbers and cereal yield and 110, 111. 112 have competition models for B. diandrus in wheat.
Brome competition with wheat reduced wheat plant weight and tillering by more than 50% over the first 71 days of growth (113). The effects of competition occur before the grain filling stage of wheat (110).
Competition with wheat didn't reduce brome plant number but did reduce brome seed output and increase stem height (114). Increased proportions of wheat reduced brome vegetative growth under good growing conditions in replacement series experiments (115).
B. diandrus more competitive than annual ryegrass and less competitive than wild oats in wheat (116) and no niche differentiation between these species (117).
B. diandrus competition in lupins reduced yield by decreasing the pod number per plant and was more competitive at high nutritional levels (118).
Little effect on medic or sub clover growth when the proportion of grass was less than 40% (119). Nutrition
Application of low P rates led to Erodium botrys dominance and higher P rates increased the brome grass in clover based pastures at Merredin WA (120).
Sulphur favours brome in clover and medic pastures, has no effect in grass or cereal swards and reduces brome in lucerne (121).
Brome reduced N and P concentrations in wheat seedlings (113). Applying Nitrogen to alleviate brome competition on cereals had little effect (113). Grazing
B. diandrus is replaced by B. hordeaceus and Vulpia myuros under heavy grazing by sheep (122).
123 and 124 have palatability data.
Origin and History:
Mediterranean.
Distribution:
ACT, NSW, QLD, SA, TAS, VIC, WA.
Belgium (125), Britain (126), becoming more common on Corsica (127), Iberian peninsula (70), recently arrive in Mexico (128), New Mexico USA (129), Portugal (130), rare in NW Russia (131), rare in Saudi Arabia(132), Spain (133, 134, 124, 135), South Africa (136)
Habitats:
Climate:
Soil:
Prefers sandy soil types.
Principal component analysis In California indicated that B. diandrus infestations were associated with specific soil characteristics (137).
Plant Associations:
Crops and pastures.
Viper's bugloss (Echium. vulgare) and Twiggy Mullein(Verbascum virgatum) in NZ (138).
Significance:
It is a common pasture plant on sandier soil types.
Beneficial:
Good quality fodder in the vegetative stages of growth.
Host for sterile red fungus which reduces take-all in cereals.
Used as a cover crop to prevent erosion in Olive groves in Spain (139, 136).
Detrimental:
Wool contaminant.
Contaminates grain including barley (140), cereals (141)
Seeds penetrate skin (142).
Sharp bristles may penetrate skin affecting meat and hide quality and cause infection. This has resulted in significant lamb losses.
Competitive weed of crops that is difficult to control in cereals.
Host for barley yellow dwarf luteovirus (BYDV-PAV and BYDV-RPV)(143), Eyespot of wheat (Tapesia, Pseudocercosporella herpotrichoides) (144), Sclerotium rolfsii (145), Take-all disease of cereals (136).
It is a poor host for Root Lesion Nematodes (Pratylenchus neglectus or thornei) and allows some build up of numbers (Vanstone & Russ, 2001).
Host for the Russian wheat aphid (Diuraphis noxia) (146).
Seeds lodge in hawks eyes in the USA (147).
Toxicity:
Not recorded as toxic. Under rare conditions nitrate levels may rise sufficiently to be of concern if large amounts are eaten by starved stock.
Physical injury by seed penetration may cause abscess and death of lambs.
Legislation:
None.
Management and Control:
There are a number of grass selective herbicides for use in broadleaf crops that give good control (148). In wheat, cultivars tolerant to metribuzin are grown in infested areas. A mixture of pendimethalin plus metribuzin pre planting gives reliable control in tolerant wheat cultivars and is more selective than metribuzin post emergence (149). Metribuzin is also used for control in barley.
Sulfosulfuron works best at the one leaf stage but stopped growth and competition when applied up to the 4 leaf stage (150).
Rotations that prevent seed set for a year or two can reduce infestations to levels that don't require control for the season of the susceptible crop.
Simazine plus paraquat provides cheap control in clover pastures (151).
Spray topping at late flowering with paraquat, mid flowering with glyphosate or early flowering with haloxyfop or fluazifop provides good control of seed set and reduced populations in the following year (87, 152).
Shallow burial of the seed over summer results in earlier and more complete germination that can be controlled with pre plant herbicides. Shallow burial in autumn also increases germination.
Delay planting crops until the main germination event has passed.
Burning provides variable control and occasionally results in greater infestations (Douglas 2003?).
Twice as much haloxyfop was required to control tillering brome compared to 3-5 leaf brome and was more effective than fluazifop at similar rates of active ingredient (153).
In lupin/wheat rotation trials in NSW, fop herbicides were best for lupins. Burning alone reduced populations in wheat by 39% and 3 cultivations reduced it by 43%. The greatest infestations occurred in direct drilled continuous wheat with stubble retention. In continuous wheat, burning stubble plus three pre plant cultivations gave good B diandrus control.(154, 155). However in Spain, B diandrus doesn't persist under zero tillage and does under minimum tillage and this is thought to be due to seed predation in the zero tillage system (156) and seed kept on the soil surface after harvest germinates before the following crop (157).
In bushland, burning provides temporary control but levels of B. diandrus returned to original levels in a year or two (158).
Thresholds:
30 -60 plants/m2 is usually worth controlling in crops. 50-60 plants/m2 reduced wheat yield by 20% in 110 trials in WA.
With sulfosulfuron, dense infestations were more susceptible than light infestations at the 2 leaf stage and vice versa at the 6 leaf stage with control being poorer in dense infestations (159).
In clover and medic pastures, apply early control when proportion of brome is greater than 40% or apply late control to stop seed set.
Eradication strategies:
Preventing seed set for 1-2 years will provide control. Mowing and cultivation is usually effective whilst burning is more variable. 500 mL/ha of glyphosate(450g/L) applied when the grass is very young or flowering is fairly selective in native vegetation, cheap and effective. Both an early and late application may be needed. For hand spraying, use 10 mL glyphosate in 10 L water and spray until just wet.
Selective control amongst broad-leaved plants can usually be achieved with 100 mL/ha Verdict®520 or 800 mL/ha Fusilade®Forte or 500 mL/ha quizalofop(100g/L) plus 1% spray oil. For hand spraying, use 100 mL of spray oil plus 2 mL Verdict®520 or 16 mL Fusilade®Forte or 10 mL quizalofop(100g/L) per 10 L water.
In bushland areas replant shrub and tree species if necessary to provide shade and help stop re-infestation.
Avoid introducing new seed in contaminated produce.
Herbicide resistance:
None recorded but properties of polymorphism, autogamy and disomic inheritance within polyploidy would favour the development of tolerance to herbicides within populations, provided selected genotypes were competitive (74).
160 has metribuzin tolerant populations in Spain.
Biological Control:
Mouse populations of 300/ha consumed 33% of Bromus diandrus seed, however because mice consumed more wild oat and barley grass seed the amount of brome in the following season increased (161).
Pseudomonas fluorescens strain D7 a root colonizing deleterious rhizobacterium reduced B. diandrus root growth on agar by 87% but had little effect in soil based tests (162).
Drechslera sp. (perfect stage, P. chaetomioides) has been considered for biocontrol but is not very effective on B. diandrus (163).
Pyrenophora semeniperda has potential as an inundative mycoherbicide to reduce brome seed set and seedling vigor (164).
A small annual hemi parasite, Triphysaria pusilla significantly reduces B. diandrus production but also attacks many other plants (165).
Related plants:
Drooping Brome (B. tectorum).
Madrid Brome (B. madritensis)
Mediterranean Brome (B. lanceolatus)
Prairie grass (B. catharticus)
Red Brome (B. rubens)
Sand Brome (Bromus arenarius)
Soft Brome (B. hordeaceus)
Soft Brome (B. molliformis)
Great Brome (Bromus diandrus) is very similar to Bromus rigidus. Both species commonly grow in the same areas and Bromus rigidus tends to be more abundant in the northern areas and on cropped land and Bromus diandrus more abundant in the southern areas and on roadsides and non agricultural areas in WA.
In B. rigidus the leaf blade has shorter and sparser hairs; the seed head is more erect, tighter (more compact) with shorter spikelet branches; the tip of the seed is pointy rather than rounded; the rachillae has elliptical rather than round abscission scars; the lemma calluses are elongated and >1 mm rather than circular and <=1 mm. B. rigidus has short and long awned varieties. Leaves of B. diandrus often have rust (Puccinia bromoides) whereas B. rigidus appear resistant (68).
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P136.
Burbidge and Gray (1970). P30. Diagram.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P68-69. Photo.
Ciba Geigy 2 P35.
Gilbey, D. (1989). Identification of weeds in cereal and legume crops. Bulletin 4107. (Western Australian Department of Agriculture , Perth). P12. Photos.
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #200.3.
Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P945.