Pacific Island Ecosystems at Risk (PIER)


Brassica napus


RISK ASSESSMENT RESULTS: High risk, score: 16


Australian/New Zealand Weed Risk Assessment adapted for Hawai‘i.
Information on Risk Assessments
Original risk assessment

Brassica napus L. Family - Brassicaceae. Common Names(s) - Rapeseed, Turnip. Synonym(s) - Brassica napobrassica (L.) P. Mill.

Answer

Score

1.01

Is the species highly domesticated?

y=-3, n=0

y

-3

1.02

Has the species become naturalized where grown?

y=1, n=-1

y

1

1.03

Does the species have weedy races?

y=1, n=-1

y

1

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

0

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

0

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

y

1

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

n

0

2.05

Does the species have a history of repeated introductions outside its natural range?

y=-2, ?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

2

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

y

4

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

y

2

4.01

Produces spines, thorns or burrs

y=1, n=0

n

0

4.02

Allelopathic

y=1, n=0

4.03

Parasitic

y=1, n=0

n

0

4.04

Unpalatable to grazing animals

y=1, n=-1

n

-1

4.05

Toxic to animals

y=1, n=0

y

1

4.06

Host for recognized pests and pathogens

y=1, n=0

y

1

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

y

1

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

n

0

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

n

0

4.10

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

n

0

4.11

Climbing or smothering growth habit

y=1, n=0

n

0

4.12

Forms dense thickets

y=1, n=0

n

0

5.01

Aquatic

y=5, n=0

n

0

5.02

Grass

y=1, n=0

n

0

5.03

Nitrogen fixing woody plant

y=1, n=0

n

0

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

y

1

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

0

6.02

Produces viable seed.

y=1, n=-1

y

1

6.03

Hybridizes naturally

y=1, n=-1

y

1

6.04

Self-compatible or apomictic

y=1, n=-1

y

1

6.05

Requires specialist pollinators

y=-1, n=0

n

0

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

n

-1

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

1

1

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

y

1

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

1

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

7.04

Propagules adapted to wind dispersal

y=1, n=-1

n

-1

7.05

Propagules water dispersed

y=1, n=-1

7.06

Propagules bird dispersed

y=1, n=-1

n

-1

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

7.08

Propagules survive passage through the gut

y=1, n=-1

y

1

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

y

1

8.03

Well controlled by herbicides

y=-1, n=1

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

Total score:

16

Supporting data:

Notes

Source

1.01

(1)It is believed that Brassica napus originated from a fortuitous hybridization between the turnip (B. rapa) and kale (B. oleracea acephala), probably in European gardens during the Middle Ages. Canola, a selected genetic variant of rape, was developed in the late 1970's in Manitoba, Canada, as a more nutritious source of vegetable oil than rapeseed. (2)Traditionally, B. napus is unsuitable as a source of food for either humans or animals due to the presence of two naturally occurring toxicants, erucic acid and glucosinolates. However, in the 1970s, very intensive breeding programs in several countries including Australia produced high quality varieties that were significantly lower in these two toxicants. The term ‘canola’ refers to those varieties of B. napus that meet specific standards on the levels of erucic acid and glucosinolates. Those cultivars must yield oil low in erucic acid (below 2 %) and meal low in glucosinolates (total glucosinolates of 30 μmoles/g toasted oil free meal) (CODEX 1999), and are often referred to as “double low” varieties.

(1)http://www.floridata.com/ref/B/bras_nap.cfm [Accessed 17 July 2008] (2)Anonymous. 2002. The biology and ecology of canola (Brassica napus). Office of the Gene Technology Regulator. Available from http://www.ogtr.gov.au/internet/ogtr/publishing.nsf/Content/canola-3/$FILE/brassica.pdf [Accessed 17 July 2008]

1.02

(1)Known only as a cultigen, sometimes escaped. Throughout temperate regions. Cultivated in most European countries, but naturalized in most. (2) Brassica napus L. -rape; navet Annual, introduced from Eurasia. Sporadic escape from cultivation. First collected at St. John, NB, by G. F. Matthew in 1874. Rare plant in cultivated and abandoned fields, roadsides, railways, and waste places in NT-M and every province from NF to BC. (3)Brassica napus, a dicot, is an annual herb that is not native to California; it was introduced from elsewhere and naturalized in the wild (4)Locally naturalised on coasts, and an occasional casual escape from cultivation on roadsides and in cultivated fields. [New Zealand]

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008] (2)http://www.cwss-scm.ca/Weeds/Weedy_mustards.htm [Accessed 17 July 2008] (3)http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1143 [Accessed 17 July 2008] (4)Webb, C.J.; Sykes, W.R. and Garnock-Jones, P.J. 1988. Flora of New Zealand Volume IV: Naturalised Pteridophytes, Gymnosperms, Dicotyledons. First electronic edition, Landcare Research, June 2004. Transcr. A.D. Wilton and I.M.L. Andres. http://FloraSeries.LandcareResearch.co.nz. [Accessed 17 July 2008.]

1.03

(1)The relative abundance of volunteer canola has increased significantly over the past three decades in western Canada (Thomas and Wise 1983; Thomas et al. 1996). This species often ranks among the most abundant weeds in these cropping systems. Weedy characteristics such as long seedbank persistence for a domesticated species contribute to the abundance and recurrence of this species as a weed. [Canola is a cultivar of B. napus] (2)Our results confirm that old cultivars of oilseed rape can persist outside of cultivated fields for at least 8–9 years after they were last cultivated and give evidence that the genetic background of feral plants on road verges does not reflect directly the genetic composition of current cultivated fields. Within the scope of transgenic oilseed rape cultivation, this study suggests that transgenic cultivars could spread and persist in natural or semi-natural habitats even if the transgene does not increase the fitness of the crop. The persistence might be even stronger if the transgene, such as one concerned with insect resistance, increases the fitness of the escaping plant

(1)Gulden, R. Volunteer Canola - Biology and Management. Available from http://www.umanitoba.ca/faculties/afs/agronomists_conf/proceedings/2007/Rob_Gulden.pdf [Accessed 17 July 2008] (2)F.D. Pessel, J. Lecomte, V. Emeriau, M. Krouti, A. Messean and P.H. Gouyon. 2001. Persistence of oilseed rape (Brassica napus L.) outside of cultivated fields. Theor Appl Genet 102: 841–846.

2.01

(1)Known only as a cultigen, sometimes escaped. Throughout temperate regions. Cultivated in most European countries, but naturalized in most. (2)Natural rapeseed (Brassica napus L.; AACC 2n=38), originated in the temperate climate of the Southwest European Mediterranean region, fails to complete its generative phase in the subtropics and is thus not cultivated in countries like Bangladesh. Adapted agroecotypes are available from the diploid representatives of its genome A (B. campestris/pekinensis, 2n=20) and C (B. oleracea/alboglabra, 2n=18). An artificial resynthesis based on carefully selected progenitor lines was expected to give a photoperiodically better adapted rapeseed. female B. pekinensis x male B. oleracea/alboglabra gave 2 hybrids and 87 matromorphous plants from 1,448 crossed flowers and the reciprocal combination gave no hybrid but 11 matromorphous plants from 2,228 pollinated flowers. The two true hybrids were vegetatively propagated and chromosome doubled. Part of the F2 was grown in Sweden (all plants flowered and the most early ones were selected), part in Bangladesh (13 out of 706 plants flowered). The selected F3 material flowered in Bangladesh and transgressions in earliness could be recorded, some lines were of definite agronomic potential. A correlation in earliness between reaction in Sweden (long day) and Bangladesh (short day) was observed.

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008] (2)Akbar, M.A. 1987. Artificial Brassica napus flowering in Bangladesh. TAG Theoretical and Applied Genetics 73(3): 465-468.

2.02

2.03

(1)Ranging from Boreal Moist to Rain through Tropical Dry to Moist Forest Life Zones, rape is reported to tolerate annual precipitation of 3 to 28 dm (mean of 90 cases = 8.3), annual temperature of 5 to 27°C (mean of 90 cases = 11.6), and pH of 4.2 to 8.2 (mean of 86 cases = 6.2)

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

2.04

No evidence (1)Oilseed rape (Brassica napus) is one of the main crops for which transgenic cultivars have been developed. It is also one of the most-invasive cultivated species in temperate countries.

(1)F.D. Pessel, J. Lecomte, V. Emeriau, M. Krouti, A. Messean and P.H. Gouyon. 2001. Persistence of oilseed rape (Brassica napus L.) outside of cultivated fields. Theor Appl Genet 102: 841–846.

2.05

3.01

(1)Known only as a cultigen, sometimes escaped. Throughout temperate regions. Cultivated in most European countries, but naturalized in most. (2) Brassica napus L. -rape; navet Annual, introduced from Eurasia. Sporadic escape from cultivation. First collected at St. John, NB, by G. F. Matthew in 1874. Rare plant in cultivated and abandoned fields, roadsides, railways, and waste places in NT-M and every province from NF to BC. (3)Brassica napus, a dicot, is an annual herb that is not native to California; it was introduced from elsewhere and naturalized in the wild (4)Locally naturalised on coasts, and an occasional casual escape from cultivation on roadsides and in cultivated fields. [New Zealand]

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008] (2)http://www.cwss-scm.ca/Weeds/Weedy_mustards.htm [Accessed 17 July 2008] (3)http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1143 [Accessed 17 July 2008] (4)Webb, C.J.; Sykes, W.R. and Garnock-Jones, P.J. 1988. Flora of New Zealand Volume IV: Naturalised Pteridophytes, Gymnosperms, Dicotyledons. First electronic edition, Landcare Research, June 2004. Transcr. A.D. Wilton and I.M.L. Andres. http://FloraSeries.LandcareResearch.co.nz. [Accessed 17 July 2008.]

3.02

3.03

(1)Volunteer oilseed rape is a major agricultural weed because its seeds can become dormant when buried in the soil. The use of phthalimides in the field to break or prevent the initiation of dormancy in rapeseeds by applying the chemical to the seed on or just below the soil surface, followed by incorporation, has been discussed [12]. Seedlings emerging could be killed by mechanical cultivation or by application of an environmentally benign herbicide. A similar approach could be envisaged using CP solutions or their active ingredients, if chemically characterised and synthesized.

(1)Thornton, M.A., T.H. Thomas & N.C.B. Peters. 1999. The promotive effect of combustion products from plant vegetation on the release of seeds from dormancy. Plant Growth Regulation 28: 129–132.

3.04

(1)Brassica napus: X Environmental weed...Naturalised and known to be a minor problem warranting control at 3 or fewer locations within a State or Territory [no impacts described]

(1)http://www.weeds.crc.org.au/documents/wdygg_Invasive%20Garden%20Plants%20list_WWF.pdf [Accessed 17 July 2008]

3.05

(1)Brassica tournefortii...Dense stands in the Coachella and Imperial valleys appear to suppress native wildflowers. Because of its early phenology, it appears to monopolize available soil moisture as it builds canopy and matures seed long before many native species have begun to flower. In coastal southern California, it locally dominates exotic grasslands in dry, open sites, especially disturbed areas. It expands over larger areas when drought suppresses other exotic annuals such as Bromus rubens, Avena fatua, Brassica geniculata, and Erodium cicutarium.

(1)http://www.cal-ipc.org/ip/management/ipcw/pages/detailreport.cfm@usernumber=12&surveynumber=182.php [Accessed 17 July 2008]

4.01

No evidence

4.02

Possibly [conflicting references] (1)The allelopathic potential of rapeseed was evaluated on germination and growth of cotton and its dominant weeds (Amaranthus retroflexus L., Abutilon theophrasti Medic.) and the possibility of herbicide usage reduction. For these purposes greenhouse experiments were performed as factorial in randomized complete block design with 4 replicates .The first factor had two levels (soil incorporated with rapeseed seedlings in 3-4 leaved stage and control soil) and the second factor had three levels (0,1.5 and 3 L/ha Cobex herbicide[N-N-Diethyl 2, 4 – dinitro - 6 – trifluoroethyl – m – phenylene – diamine]). Also, six weeks after incorporation of rapeseed with soil water extracts were prepared from soil on a weekly basis. The effect of these extracts on growth and germination of above plant were investigated in Petri dishes.
The results showed that A.retroflexus and A.theopherasti germination was reduced through rapeseed treatment but cotton germination had no change. Thirty or 60 days after planting (DAP) was observed significant reduction in growth of A. retroflexus and A. theophrasti and dry weight of cotton. However 60 DAP there were no changes in growth of cotton even fresh and dry weight of cotton through rapeseed treatment was more than control soil. Study in petri dish proved that the third, the forth and fifth week extracts had the most significant effects on the growth reduction. This is probably due to releasing of some growth inhibitor substance from decomposed rapeseed. (2)The allelopathic potential of Brassica species has been attributed to release of the mustard oil glycosides which they produce in large quantities. Upon hydrolysis, these glucosinolates yield isothiocyanates, compounds with strong antibiotic properties. The objective of this study was to assess whether Brassica napus, a common and widespread crop and weed crucifer, is capable of allelopathic interference, and if so, whether its glycoside derivative, allyl isothiocyanate (AI), is capable of producing this interference. Wild type and low glucosinolate-mutant B. napus were grown in low organic content soil under greenhouse conditions, and AI release into soil was monitored. Most plants released low levels of AI, though approximately 10% released much higher levels. Wild type plants released more AI than mutants. Growth of the target species, Medicago sativa, was not affected by additions of AI to soils at concentrations equal to the median and 95% quantile from the B. napus soils. In replacement series experiments, the two B. napus genotypes suppressed growth of M. sativa equally despite differences in AI release rate. In an intraspecific replacement series experiment, the two B. napus genotypes were equal competitors. Under our experimental conditions, B. napus showed no indication of being allelopathic, and AI concentrations typical of soils around B. napus plants did not inhibit target plants.

(1)Younesabadi, M. 2005. Study of allelopathic interference of rapeseed (Brassica napus var.belinda) on germination and growth of cotton (Gossypium hirsutum) and it’s dominant weeds.Proceedings of the 4th World Congress on Allelopathy, eds JDI Harper, M An, H Wu and JH Kent, Charles Sturt University, Wagga Wagga, NSW, Australia. August 2005. International Allelopathy Society. (2)Choesin, D. N. and R. E. J. Boerner. 1991. Allyl Isothiocyanate Release and the Allelopathic Potential of Brassica napus (Brassicaceae). American Journal of Botany 78(8): 1083-1090.

4.03

No evidence

4.04

(1)Although rape is outlined here due to its usefulness as a vegetable, it has been grown primarily for green livestock fodder

(1)http://edis.ifas.ufl.edu/MV123 [Accessed 17 July 2008]

4.05

(1)Irritant poisoning of stock can occur with acute or hemorrhagic gastroenteritis. Rape seed, containing the goitrogenic L-5-vinyl-2-thiooxazolidone, can produce goiter in animals consuming modest quantities. Rape has been incriminated in several poisoning syndromes, i.e. respiratory, digestive, nervous, and urinary.

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

4.06

(1)Following fungi are known to cause diseases in rape: Albugo candida, A. macrospora, Alternaria brassicicola, A. brassicae, A. oleracea, A. tenuis, Botrytis cinerea, Cercospora brassicicola, C. armoraciae, Cercosporella brassicae, Cylindrosporium brassicae, Cytopus candidus, Erysiphe communes, E. polygoni, Leptosphaerella napi, Mycosphaerella brassicicola, Ophiolobus graminis, Pernonospora parasitica, P. brassicae, Plasmodiophora brassicae, Phoma lingam, P. napobrassicae, P. oleracea, Phyllosticta brassicae, Pythium debaryanum, P. perniciosum, Rhizopus oryzae, Rhizoctonia solani, Sclerotinia libertiana, S. fuckeliana, S. sclerotiorum, Stemphylium consortiale, Tuberculariella brassicae. Viruses causing diseases of rape include: Argentine sunflower, Cabbage black-ring, Cauliflower mosaic, Cucumber mosaic, Trinidad cucumber mosaic, Turnip crinkle, Tobacco mosaic, Yellow spot of Nasturtium. Bacterial diseases are caused by Pseudomonas destructans, P. maculicola and Xanthomonas campestris. Insects are major pests of rape; sprayings should be planned and official recommendations followed. Fleabeetles, cutworms, red turnip beetles attack seedlings, and these, along with Diamondback moth, Beet webworm, Bertha armyworm and Imported cabbage worm, attack from bud stage until maturity. Red-legged earth mite (Halotydeus destructor), in western Australia, Cutworms (Agrotis spp.); Cabbage moth (Plutella xylostella); Rutherglen bug (Nysius vinitor); aphids; weevils (Listroderes costirostris); Cabbage white butterfly (Artogeia rapae); Australian budworm (Heliothis punctigera). Nematodes include Ditylenchus dipsaci, Helicotylenchus pseudorobustus, Heterodera crucifera, H. schactii, Meloidogyne artiellia, M. hapla, M. javanica, M. sp., Nacobbus aberans, Pratylenchus neglectus, and P. penetrans (Golden, p.c., 1984)

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

4.07

(1)Rapeseed has been linked with adverse effects in asthma and hay fever sufferers. Some suggest that oilseed pollen increases breathing difficulties. But this is unlikely as rapeseed is an entomophilous crop, with pollen transfer primarily by insects. Others suggest that this is caused by the inhalation of oilseed rape dust[4], and that allergies to the pollen are relatively rare. It may also be that since rapeseed in flower has a distinctive and pungent smell, hay fever sufferers wrongly blame the rapeseed just because they can smell it. An alternative explanation may be that it is simply the sheer volume of rapeseed pollen in the air around farmland which triggers an allergic reaction in hayfever sufferers on inhalation, or following prolonged exposure to high levels.

(1)http://en.wikipedia.org/wiki/Rapeseed [Accessed 17 July 2008]

4.08

No evidence

4.09

(1)Light: All of the B. napus varieties should have full sun for maximum performance.

(1)http://www.floridata.com/ref/B/bras_nap.cfm [Accessed 17 July 2008]

4.10

(1)Requires fertile, well-drained soils.

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

4.11

4.12

No evidence

5.01

Terrestrial

5.02

Brassicaceae

 

5.03

Brassicaceae

 

5.04

(1)Brassica napus is a variable species, divided into three groups or subspecies: B. n. napobrassica includes the rutabagas (a.k.a. Swedes in England), grown for their enlarged turniplike swollen stems;

(1)http://www.floridata.com/ref/B/bras_nap.cfm [Accessed 17 July 2008]

6.01

No evidence

6.02

(1)Propagation Methods:From seed

(1)http://davesgarden.com/guides/pf/go/79575/ [Accessed 17 July 2008]

6.03

(1)Both rapes can be cross-pollinated with other wild Brassica such as Charlock and wild mustards

(1)http://www.ienica.net/crops/oilseedrapeandturniprape.pdf [Accessed 17 July 2008]

6.04

(1)Rape is 70% self-pollinating and 30% cross-pollinated.

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

6.05

(1)Even if wind and insects are absent, seed are still produced. Yield increases with honeybees. Competes with alfalfa and clover for insect pollination.

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

6.06

No evidence

6.07

(1)Annual or biennial, when sown late and flowering the following spring, with slender or stout, hard, long, fusiform tuberous taproot

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

7.01

(1)Evidence for seed limitation in these motorway verge populations comes from the observation that population densities were significantly higher on the side of motorways carrying traffic towards the oilseed crushing factory at Erith in Kent. This pattern was similar in 1993 and 1994, and suggests that oilseed rape recruitment depends, at least in part, on the introduction of seed spilled from loaded lorries in transit. Consistent with this hypothesis is the further observation that population densities were higher at junctions (i.e. in the verges between the exit and entry slip roads), where braking and turning might be expected to cause more seed to be shed.

(1)Crawley, M. J. and S. L. Brown. 1995. Seed Limitation and the Dynamics of Feral Oilseed Rape on the M25 Motorway. Proceedings: Biological Sciences 259(1354): 49-54.

7.02

(1)Grown sparingly for young leaves used as potherb; more generally grown as forage for livestock feed, and as source of rapeseed oil. Rape oil used in food industry, as an illuminant and lubricant, and for soap manufacture. Residual rapeseed cake, though low in food value, used as livestock feed. Rapeseed oil has potential market in detergent lubrication oils, emulsifying agents, polyamide fibers, and resins, and as a vegetable wax substitute. According to the Chemical Marketing Reporter (April 26, 1982) "the most common use for the oil is still in the production or erucic acid, a fatty acid used in turn in the manufacture of other chemicals. Sprouts are used dietetically and as seasoning.

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

7.03

(1)Weed: also potential seed contaminant [possible]

(1)http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?7661 [Accessed 17 July 2008]

7.04

(1)silique 5–11 cm long, 2.5–4 mm wide, with slender beak 0.5–3 mm long [no mechanisms for wind dispersal]

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

7.05

Unknown

7.06

Not fleshy fruited

 

7.07

No means of attachment

 

7.08

(1)Sheep and other livestock are capable of ingesting seeds from weeds and desirable pasture species and excreting a percentage of viable seeds. As livestock are used to graze stubble paddocks after harvest, any crop seed shed before harvest or spilt during the harvesting process could also be ingested and subsequently excreted as viable seed. Knowledge of the rate of passage and viability of crop seed ingested by livestock is critical for good farm hygiene so that seeds are not inadvertently spread from the source paddock. Merino wethers were placed on a diet containing whole canola seed (10% total dry matter), and faeces were collected while canola was in the diet and for a further 6 days after canola was removed from the diet. Seed was found to pass through the wethers in less than 1 day, and reached a constant level after 2 days. When canola seed was removed from the diet, the majority of seed was passed during the first 2 days, but seed was excreted for up to 5 days. Seed germinability was reduced after 1 day, and further still after 2 days, but did not significantly decrease after this. While sheep are capable of excreting germinable canola seeds for up to 5 days after they were last included in the diet, use of a 7–10-day holding period will ensure that canola is not inadvertently spread beyond the grazed stubble paddock.

(1)Stanton R. , Pratley J. , Hudson D. 2003. Sheep are potential vectors for the spread of canola (Brassica napus) seed. Australian Journal of Experimental Agriculture 43, 535–538.

8.01

(1)Seed yields vary from 900 to 3,000 kg/ha; in North Africa it may be only 300–350 kg/ha. Rapeseed contain an average of 40% oil on a dry matter basis. [unlikely outside cultivation]

(1)http://www.hort.purdue.edu/newcrop/duke_energy/brassica_napus.html [Accessed 17 July 2008]

8.02

(1)Persistence of canola seed is considerably longer in undisturbed soils compared to cultivated soils (Chadoeuf et al. 1998). Studies in the Northern Hemisphere have reported viable seeds of canola persisting in disturbed soils for at least 5 years and possibly up to 10 years or more in undisturbed soil (Masden 1962); (Pekrun et al. 1997a); (Vaughan et al. 1976). Light sensitivity in canola seed is the major factor contributing to a shorter persistence of seeds in cultivated soils. Persistence will also vary between soil types...Large seedbanks of canola can build up in the soil as a result of high amounts of seed losses before and during harvest. Other mechanisms responsible for adding seed to the seedbank include ungerminated seed from sowing, seed produced from volunteers and/or seed losses from mature plants due to heavy rainfall, hail, strong winds or lodging.

(1)Anonymous. 2002. The biology and ecology of canola (Brassica napus). Office of the Gene Technology Regulator. Available from http://www.ogtr.gov.au/internet/ogtr/publishing.nsf/Content/canola-3/$FILE/brassica.pdf [Accessed 17 July 2008]

8.03

Possibly not if modified for herbicide resistance. (1)A field in which Brassica napus volunteers were not controlled by several applications of glyphosate was investigated in 1998. This field had been planted with glufosinate-resistant and imidazolinone-resistant B. napus in 1997 and was adjacent to a field that had grown glyphosate-resistant B. napus. Mature volunteer B. napus were collected on a 50- by 100-m grid in the field. Progeny from 34 volunteers were sprayed with glyphosate at 440 g ae ha−1, and the survivors were sprayed with either glufosinate or imazethapyr at 400 or 50 g ai ha−1, respectively. Where seed numbers permitted (14 volunteers), seedlings were also sprayed sequentially with glyphosate, glufosinate, and imazethapyr, at 440 g ae ha−1, 400 g ai ha−1, and 50 g ai ha−1, respectively. In total, 15 volunteers had progeny that were between 66 and 82% resistant to glyphosate, consistent with the predicted 3:1 resistant : susceptible ratio. Volunteer B. napus plants with glyphosate-resistant seedlings were most common close to the putative pollen source; however, a plant with glyphosate-resistant progeny was collected 500 m from the adjacent field edge. Seedlings from all nine volunteers collected from the glufosinate-resistant area showed multiple resistance to glyphosate and glufosinate, whereas seedlings from 10 of 20 volunteers collected from the imidazolinone-resistant area showed resistance to imazethapyr and glyphosate. DNA extraction and restriction fragment length polymorphism (RFLP) analysis of seedlings confirmed that mature B. napus volunteers were hybrids resulting from pollen transfer rather than inadvertent seed movement between fields. Two seedlings from the 924 screened were resistant to all three herbicides. Progeny from these self-pollinated individuals were resistant to glyphosate and glufosinate at the predicted 3:1 resistant : susceptible ratio and resistant to imazethapyr at the predicted 15:1 resistant : susceptible ratio. Sequential crossing of three herbicide-resistant varieties is the most likely explanation for the observed multiple herbicide resistance. Integrated management techniques, including suitable crop and herbicide rotations, herbicide mixtures, and nonchemical controls should be used to reduce the incidence and negative effect of B. napus volunteers with multiple herbicide resistance.

(1)Hall L, Topinka K, Huffman J, Davis L, Good A. 2000. Pollen flow between herbicide-resistant Brassica napus is the cause of multiple-resistant B. napus volunteers1. Weed Science 48(6): 688–694.

8.04

Unknown

8.05

Unknown


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