Wild Radish

Raphanus raphanistrum L.

Synonyms - Raphanus raphanistrum is sometimes treated as an aggregate and includes Raphanus maritimus and others as subspecies.

Family: - Brassicaceae.

It was previously known as the Cruciferae family

Order: - Capparales.

Names:

Raphanus is from the Greek ra and phanomai meaning to quickly appear and refers to the rapid germination and growth of seedlings and also is the Greek name for radish. Raphanistrum has the suffix -istrum meaning 'like', thus it is the species like radish. The common name, Wild Radish, has a similar derivation.

Other Names:

Cadlock

Jointed Charlock (USA)

Jointed Radish

Oleiferous Radish

Ramnas (South Africa)

Runch (UK)

Wild Charlock

Wild Kale

Wild Turnip

White Charlock

White weed

Summary

Wild Radish is an erect, annual, much branched herb to 1.5 metres tall, that is bristly toward the base and arises from a dense rosette of stalked, lobed, rough-to-touch leaves that usually wither before flowering. The stem leaves are smaller. It has 4 petalled, white, yellow or lilac coloured flowers with 6 stamens. The petals do not overlap.

The seed pods are 20-90 mm long, ribbed and distinctly constricted between the seeds and break up into single-seeded bony pieces at maturity. The narrow conical tip (beak) lacks seeds

Native to the Mediterranean and it is a become common weeds of roadsides and disturbed areas near cultivation but only occasionally invades bush. It flowers at most times of the year with a flush in spring.

Description

There are three major forms based on flower colour. These are yellow, white or lilac with dark veins.

Cotyledons:

Two, but about 5% of plants may have more than two 758. Heart shaped. 8-15 by 10-20 mm. Tip indented. Base tapered. Hairless. Stalk 10-25 mm long. Short hypocotyl. Epicotyl may be present or absent.

First Leaves:

Oval. 20-100 mm long. Stalked. Tip round. Edge usually toothed or lobed, especially near the base. Short rough stiff hairs. Prominent veins.

Leaves:

The early leaves form a flat rosette.

They have a strong turnip or radish like odour when crushed.

Alternate.

Rosette leaves:

Withered by flowering time.

Stipules - None

Petiole - Long and slender.

Blade - 50-400 mm long by 20-150 mm wide, soft but rough to touch, green to bluish green. Deeply lobed with larger, rounded lobe at tip of leaf and 1-6 pairs of side lobes, each set progressively smaller toward the base. Toothed edges. Base tapered to squarish and offset. Usually with short rough stiff hairs.

Stem leaves:

Stalked. Up to 350 mm long at base, shorter above. Lower leaves covered with prickly hairs and lobed with a rounded terminal lobe as wide as the leaf. Upper leaves smaller and often without lobes.

Amphistomatic.

High cuticle thickness on the upper side of the leaf is a barrier to herbicide penetration 759.

Stems:

Erect. 500-1500 mm. Bluish green and often reddish at the base. Branch from near the base and along their length. Lower portion has stiff downward pointing, transparent bristles. Solid maybe with a pithy core. Flexible and slightly angled, round or fluted with shallow lengthwise grooves.

Flower head:

Long and open, in racemes on the ends of branches.

Flowers:

Ovary - Superior.

Sepals - 4. 5-10 mm long. Erect, outer ones pouched at the base and may contain nectar.

Petals - Yellow, white, cream, purple, lilac, yellowish brown or rarely pink, often with distinct light or dark veins. Petals are 12-20 mm long and wide and clawed. The 4 petals don't overlap or touch and alternate with the 4 sepals.

Stamens - 6

Anthers - Yellow.

Produce pollen and nectar simultaneously 760.

Pollen varies in colour from yellow to orange 761.

White flowers are a species specific dominant trait and yellow flowers are a recessive trait 762. Flower colour is determined by a single gene locus 763.

It is rare for more than 30% of flowers to set pods and early pollination reduces flower number 764.

Fruit:

Erect, lengthwise ribbed pod (siliqua) on a 15 mm stalk spreading away from the stalk, Pod 30-80 by 2.5-6 mm, yellowish brown when mature. Constricted between the seeds. Ribbed. Breaks into 1-10 one-seeded bony segments, 3-7 mm long by 2-5 mm wide. The pointed, conical, seedless beak (tip) is 12-30 mm long.

The number of seeds per fruit varies between ecotypes 765.

Seeds:

Globular to egg shaped, 2-4 mm diameter, red-brown to yellowish. Fine network veined surface. Flesh is yellow. 1.5-12 mg each. Seed weights may vary by a factor of 20 and is determine largely by environmental conditions rather than genetics according to 766 and determined by genetics, pollen donor, time of seed production )early seed larger than late), resource demands prior to fruit set, density and timing of pollination (early, heavy pollination gives fewer flowers and smaller seed), number of seed per pod, and seeds in stylar position were smaller according to 767.

Seed proteins can be used for identification with electrophoregrams 768

Roots:

800-1600 mm long, tapering taproot, with many fibrous laterals in the top 200 mm of soil. Tastes like cultivated radish.

Does not support vesicular arbuscular mycorrhizal fungi.

Key Characters:

No seed in the beak of the pod.

Pod constricted between the seeds and breaks into single seeded bony segments.

Seed is not shed from the pod segments.

4 coloured petals that don't overlap or touch.

4 sepals that alternate with the petals and are pressed against the petals.

6 stamens

769 has reviewed the taxonomy and sub species.

770, 771 has used DNA mapping to show the relationships between various Brassicas.

Biology

772 has reviewed older research.

Life cycle:

Annual or sometimes biennial. It germinates anytime sufficient moisture is adequate with a flush of seedlings in autumn to early winter. Seedlings normally emerge 4-5 days after imbibition. The young plant develops as a relatively flat rosette. Production of the flowering stem, flowering and senescence is governed by temperature, day length and soil moisture. It requires less than 600 degree days to flower. It will flower at any time of the year depending on when the plant germinated. Summer germinating plants will flower within 30 days whilst those germinating in winter may take over 100 days before flowering 773. In winter crops, the majority of Wild Radish germinates soon after cultivation or planting, grows as a rosette for 3 months then produces a flowering stem which bears flowers about a month later and continues flowering until summer drought causes senescence. Seeds ripen progressively from the base of the flower head. A plant may have ripe seeds and still be producing flowers.

774 has a decimal growth stage scale for Wild Radish.

Physiology:

Temperature is the main factor controlling development until flowering. A combination of temperature, day length and soil moisture determine the onset of flowering and senescence.

Chromosome number is 2n=18.

It is not generally colonised by mycorrhizal fungi.

Produces glucosinolates in response to insect attack and the levels may double following caterpillar attack 775.

Plants evolve frost resistant or frost tolerant ecotypes in frosty environments 776.

Growth and yield decreased as salinity increases 777

After one month, leaf area index is 1 and dry weight is 130 g/m2 and in 4 months LAI is 6 and dry weight 4 kg/m2. Dry weights are about 33% more than wheat in the same conditions 778

2,4-D had little effect on leaf starch content, increased protein and decreased sugar contents at 7-11 days after spraying 779. MCPA reduced starch and sugar contents of leaves and increased protein content 7-11 days after application 780.

Reproduction:

Wild Radish is hermaphroditic 781 and self incompatible 782. A gametophytic gene and sporophytic locus is responsible for self incompatibility 783, 784, 785, 786.

Fruit and seed set is often variable due to self incompatibility or poor pollination. It is mainly pollinated by honey bees, small native bees (mainly Ceratina and Dialictus 787, butterflies (mainly Pieris rapae) syrphid flies 788 and aphids. It is outcrossing and not pollinated by wind. In Australian trials, 50 plants/m2 produced 3,000 seeds/m2 in one year and 17,000 seeds/m2 in the next. 10 plants/m2 produced about a third of these quantities. A single plant/m2 produced just under 300 seeds and up to 45,000 seed/m2 have been recorded in dense stands (Reeves et al,1981). Annual seed sets are generally from 1000-20000 seeds/m2.

Wild radish germinating in May produced 789 seeds/plant which was 4 times more seed than those germinating in June and over 100 times more seed than those germinating in September (Cheam, 1986). In the presence of a competitive crop seed production from late germinating wild radish is severely diminished. In lupins, radish which germinated more than 21 days after the crop did not produce any seed 789. This finding is questioned by field workers in WA but has not been tested. In Canola, Wild Radish emerging 10 weeks after the crop still produced seed in one out of two years in NSW 790.

Seed production is not reduced when up to 50% of leaf material is removed 791.

Cabbage White Butterfly is the main pollinator and prefers yellow over white flowers 763.

Flowering times:

Any time of the year, with a flush in spring.

Around 600 degree days after germination.

A major gene effect seems to determine the days to flowering 781, 765

Seed Biology and Germination:

Seeds may remain dormant in the soil for many years. Seeds from the warmer northern areas are (genetically) less dormant than seeds from southern areas 89. Seeds from the yellow form have around 50% dormancy and are less dormant than those from the white or lilac forms with 85% dormancy (Cheam, 1984).

Seeds prefer moist, dark conditions for maximum germination and will germinate over a wide range of temperature conditions. Exposure to light before burial to 10 mm and removal of the seed from the pod segment improves germination.

Deep burial induces dormancy and increases seed longevity. 45% of seed will survive 4 years when buried 100 mm deep, but this rapidly declines to low levels by six years. On the surface, most seed is lost in the first year or two but some will last up to 5 years.

Early germinating plants produce more seed and a greater proportion of dormant seed.

Seed weights vary from 1.5-12 mg/seed. Larger seeds grow more rapidly and have a greater seed output than smaller seeds (Stanton, 1984).

Around 5% of seed will germinate if left undisturbed on the soil surface. A 10 mm deep cultivation at the break of the season results in around 20% of seed germinating. This is due to darkness and a better moisture regime rather than the physical effects of cultivation. Deeper cultivations result in around 10% germination (Cheam, 1986).

Seed contained in the pod segment is 5-10 times more dormant than free seed. This may be due to a non leachable inhibitor or physical restriction. The seed coat also imparts dormancy t some seeds and damaging the seed coat results in greater levels of germination. 792 has further data on this and maximum depths for emergence.

Seeds in the field pass through cycles of varying dormancy. Freshly shed seed is highly dormant, this decreases with time until autumn then increases with decreasing temperature. This dormancy can be reduced by shallow burial either soon after seed drop in summer or in autumn.

Plants that emerge early in the season produce more dormant seed 89.

Seed will germinate over a range of temperatures from 5o to >35oC with an optimum of 20oC. Best germination occurs under wide diurnal changes in temperatures of 25/10oC in some studies and 15/10 deg C with 19% germination in 22. 20-99% germination at 20/10 deg C with de-hulled seeds having higher germination percentages and stratification having little effect 793.

794 has a model for Wild Radish emergence based on weather data and WEEDEM model has been used in WA to predict wild radish emergence 795 and a mechanistic model has been used in Victoria 796.

A major gene effect seems to determine emergence time 781

Central ovules in the pod are fertilised before distal ones and attain a greater seed size 797.

Seeds stored at 10, 20 or 10/20 deg C had greater germination after storage for 6 and 12 months 21

Reductions in light levels due to increased crop (barley or maize) and weed canopy doesn't reduce germination but does reduce growth of late emerging Wild Radish 798, 798.

Lemon grass extracts inhibit wild radish germination 799.

Seeds from small sections of the pod have poor (10%) germination. Segements close to the stem had larger seeds and earlier germination the those at the ends of pods 800.

Vegetative Propagules:

Wild Radish does not reproduce vegetatively. However, it will re shoot from the taproot if aerial portions are damaged.

Hybrids:

No hybrids have been recorded in Australia though it is known to hybridise with Sea Radish (R. maritimus) and cultivated Radish (R. sativus) 683.

Forms complex hybrids with Canola which can carry glufosinate tolerance and other transgenes into weedy hybrids 801, 802, and after 4 generations plants almost identical to Wild Radish but containing the new genes could be produced 803. Amphidiploids where all the genes of Wild Radish plus those of Canola can occur 804. Canola will cross with a number of cruciferous weeds including Wild Radish but the hybrids are generally of poor vigour and not likely to be of environmental concern. 805.

806, 807, 808 have looked at gene flow from Canola to Wild Radish in Australia.

809 indicate that hybrids between Wild Radish and Canola are unlikely to naturalise because of their poor vigour and high sterility levels. However, hybrids and gene flow for Wild Radish to cultivated Radish is expected.

810 has also analysed gene flow from canola to weedy Brassicas including wild radish.

811 has a review of gene flow from European research.

812 has a gene map for Wild Radish. 813 has genetic fingerprints for a number of Raphanus types.

Allelopathy:

Wild Radish aqueous extracts and incorporated residues are allelopathic to some plants 814 but field problems are rare and in some cases the crop is given an advantage over the weeds by Wild Radish effects e.g. Tomatoes with Yellow Nutsedge 815. 816 reported that 1% tissue extracts were not considered allelopathic to Lucerne of Perennial Ryegrass seedlings or germination.

Wild Radish seed in grain can reduce its viability 817

Wild Radish Ecology, Population Dynamics and Dispersal:

Origin and History:

Mediterranean origin 818.

It spread from the Mediterranean through Europe with the cultivation of cereal rye over 2000 years ago and was introduced to Britain in Roman times. It is widespread in most temperate climates of the world.

It was introduced to Australia in the mid 1800's probably as a contaminant of agricultural produce.

It was recorded as being naturalised around Melbourne in 1860, Sydney in 1867, Adelaide in 1875 and Queensland by 1913.

It was proclaimed under the Quarantine Act in 1909.

Distribution:

ACT, NSW, QLD, SA, TAS, VIC, WA. 819.

Wild Radish is the third most widely spread and serious weed of broad acre cropping in Australia 820. (Annual Ryegrass and Wild Oats are worse).

Spread rapidly during the 1970's in NSW 821.

Australian surveys include 40, 724

Significant weed of Brazil 822, Canada 823, 824, Chile 825, Czechoslovakia 826, Egypt 827, France 828, Germany 829, Italy 830, Latvia 831, 832, Lebanon 833, Poland 834, 835, Portugal 181, Norway 836, Romania 837Spain 838, 839, 840, 133 Sweden 841, third most common weed of wheat in Turkey 842, USA 843, USSR 844, Western Himalayas at 1200-1800 m 845

Habitats:

It is a common weed of cultivated winter crops, roadsides and disturbed areas. It tends to decline in pastures due to competition, grazing and lack of disturbance or cultivation which stimulates germination.

Climate:

Temperate regions and up to sub alpine areas.

Soil:

Prefers fertile soils with high soil nitrogen levels.

Grows on all soil types from sands to clays but avoids the calcareous or alkaline soils.

Prefers acidic soils 846.

Plant Associations:

Prefers cultivated cropping areas but persists on undisturbed sites in the absence of grazing or strong competition. It usually survives at low levels in temperate grazed pastures and builds up during a cropping phase.

It is commonly associated with Annual Ryegrass (Lolium rigidum), Wild oats (Avena fatua, A. ludoviciana, A. sterilis), Capeweed (Arctotheca calendula), Spiny Emex (Emex australis) and Wireweed (Polygonum aviculare).

Significance:

4 million hectares of Wild Radish are sprayed each year in Australia with about $40M worth of herbicide.

Beneficial:

Pollen source for bees 847, 848.

Source of early feed.

Used as a salad vegetable in Turkey and has antioxidant and Iron chelating properties 849 and in Sicily 850.

Used as a green manure 851

Hosts predators of cabbage aphid thereby helping to keep numbers of the aphid down.

Does not host Root Lesion Nematode (Pratylenchus thornei) 63.

May have some anthelmintic action to help reduce parasites in stock 852.

May be a source of genes for Blackleg resistance in Canola but some isolates still affect Wild Radish 853.

Extracts can be used to control White Fly 854.

Provides pollen for predatory mites which may be important in Citrus orchards 855.

Green manuring Wild Radish (to make use of the glucosinolates) and solarization to kill Wild Radish seed is providing good control of weeds and pathogens in Strawberries in Italy 856

Root extracts contain anti fungal agents857.

Detrimental:

Wild Radish is the third most widely spread and serious weed of broad acre cropping in Australia 820, 858. (Annual Ryegrass and Wild Oats are worse).

Wild Radish probably costs Australian grain producers around $500 million per year.

Wild Radish is a competitive weed of crops causing yield reductions. 10 plants/m2 typically reduce wheat yields by 10% and 200/m2 cause a 50% yield reduction (Moore, 1979). Losses of up to 80% have been recorded (Dellow and Milne, 1987). This, together with its widespread distribution, and abundance makes it one of the most serious weeds of cropping.

It is a common contaminant of cereal, pulse and canola grain 859, 860 and hay 861. Pod segments are similar in size to cereal grain and difficult to remove mechanically. Seedlings establish early in the season and are very competitive. Successive germinations over the year replenish those that have been controlled by herbicides or other methods.

Thick infestations of radish can cause harvesting problems by choking the harvester or contaminating the grain with green material.

In some years, green radish seed, pods and stem fragments in the harvested grain can increase moisture contents above the levels acceptable for delivery and storage.

Green wild radish pod segments reduces the germination of contaminated cereal, lupin and pea seed. A 5% contamination level reduced wheat germination by 40 to 100% and barley germination by 70 to 100%. A 10% contamination level reduced lupin germination by 100% and pea germination by 98% Effects are greater with high levels of contamination, high temperatures and longer storage periods. The effect on germination usually occurs within 2-3 days of harvest or storage. The toxin kills the crop seed or causes abnormalities of the seedling 817.

Contamination of Canola by Wild Radish increases the undesirable erucic acid content of the Canola seed and the glucosinolate level of the meal to levels that are unmarketable even though the Wild Radish per se has no effect on the Canola seed directly 790.

Taints milk and meat.

It is an alternative host for insects like Cabbage(Diamondback) Moth 862, Cabbage Seed Pod Weevil 863, Cabbage White Butterfly 864, 865, Cabbage Root Fly 866, Circulifer haematoceps 867, Green Vegetable Bug 868, Kale Leaf Worm 869, Nezara viridula 870, Redlegged Earth Mite, Rhytidoderes plicatus 871, Thrips 872, 873, Vegetable Weevil, Aphids and Flea Beetle. Thrips breed up on flowering Wild Radish in spring 874.

White Italian Snails also feed on it.

It is an alternative host for diseases of canola, Brassica and other crops. In WA, 3 aphid borne viruses, Beet Western Yellows Virus (BMYV) 875, 876, Cauliflower Mosaic Virus (CaMV) and Turnip Mosaic Virus (TuMV) 877, have been found in Wild Radish and adjacent Canola 878. It also hosts Blackleg, Black Rot (Xanthomonas campestris), BNYVV (beet necrotic yellow vein furovirus) 879, Bacterial Streak and Bulb Rot of Onions 880 Cucumber Mosaic Virus (CMV) 881, Downy Mildew (Peronospora parasitica), Powdery Mildew of Brassicas (Erysiphe cruciferarum) 882, Rhizoctonia 883, Verticillium Wilt 884, Tobacco Streak Virus, tomato spotted wilt virus</i> (TSWV) 885, turnip yellow mosaic tymovirus (TYMV) 886, tobacco yellow dwarf virus (TYDV or Bean Summer Death Virus) 887 White Rust (Albugo candida), and possibly club root.

It is a good host for Root Lesion Nematode (Pratylenchus neglectus) allowing numbers to build up 63.

Serious and difficult to control in organic vegetables 888.

Weed of Apples 181, Aspragus 838, 825, Beans, Cabbage 823, Buckwheat 832, Cherry 181, Chickpeas, Cotton 889, fodder borecole 890, Lentils, Lucerne 891, maize 837, Onions 892, Peach 181, Pears 181, Peas, Spinach 828 Strawberries 893, Squash 823, Tobacco 894, vegetables 39

Toxicity:

The seed is toxic and contains an isothiocyanate derived from glucosinolate.

Poisoning of lambs grazing flowering wild radish and cows forced onto luxuriant growth have been recorded. The case of cattle losses in Geraldton occurred after unusual summer rains caused luxuriant growth and cattle were used to graze it down in March and April. However, it is rarely a problem in normal field situations and is even valued by some farmers for its early rapid growth. In feeding tests, freshly cut green material containing up to 600 g of ripe seed did not affect lambs, pregnant ewes or adult sheep.

5% radish pods in pig diets did not cause any toxicity but did reduce feed conversion ratios and daily weight gain 895.

Symptoms:

Lambs - jaundice, haemoglobinuria (red water) liver damage, loss of rumen muscle tone.

Cattle - Loss of appetite and condition, lassitude, stupor, paralysis, excitability, mucous coated dung, blood stained diarrhoea, diffuse exudation and encrustation of the nose. Some cases of abortion and oedema of the brisket.

Treatment

Remove stock from Wild Radish infested area.

Don't feed cereal screenings containing significant quantities of wild radish seed to stock.

Legislation:

It was proclaimed under the quarantine act in 1909. It is a declared weed in limited areas of NSW and SA. Its widespread distribution and abundance has resulted in it being dropped from most enforced control programs.

Prohibited weed of India which has trade implications 896.

Wild Radish Management and Control:

Related plants:

Cultivated Radish (Raphanus sativus). Seeds can be distinguished by seed coat characters 897.

Sea Radish (Raphanus maritimus).

The native Brassicaceae species usually have short, broad and smooth pods.

Plants of similar appearance:

Capeweed (Arctotheca calendula) has yellow flowers with many petals and the underside of the leaves in much paler or whitish.

Charlock (Sinapis arvensis)

Indian Hedge Mustard (Sisymbrium orientale)

Mediterranean Turnip (Brassica tournefortii)

Radish (Raphanus sativus)

Rapistrum (Rapistrum rugosum)

To distinguish Wild Radish from Charlock;

Wild Radish has the sepals pressed against the back of the petals; the petals are longer, narrower, a paler yellow or not yellow or are veined and don't overlap or touch; the young leaves are rough, with somewhat indented veins with a more rounded leaf tip and usually lobed at the base; the rosette tends to lie flat.

Charlock has widely spreading sepals, shorter, narrower, brighter, veined yellow petals that overlap and have no obvious veins; young leaves are shinier, smoother with a less rounded leaf tip and the first leaf usually has no basal lobes; the rosette leaves tend to be semi erect and the veins are less indented.

The seedlings of Wild Radish and Charlock are difficult to confidently separate.

To distinguish Wild Radish from Wild Turnip:

Wild Radish has no 'warts' on the upper surface of its first leaves and are longer and narrower; rosette leaves persist for some time after the flowering stem emerges; stem leaves are more abundant, persistent and don't clasp the stem; the sepals are pressed against the back of the petals; the petals are longer, narrower, a paler yellow or not yellow or are veined and don't overlap or touch; the ripe seed pod breaks into segments and doesn't release the seed freely; the seed is larger;

Wild Turnip has 'warts' on the upper surface of its broader first and rosette leaves; the rosette leaves wither soon after the emergence of the flowering stem; stem leaves are sparse and clasp the stem; the sepals stand away from the petals; the petals are shorter, broader, smaller, occasionally overlapping, not obviously veined and yellow fading to almost white; the ripe seed pod splits lengthwise from the base to release the smaller free seeds.

To distinguish Wild Radish from cultivated Radish:

Leaves and stems of both species are quite similar.

Wild Radish sometimes has white flowers; the seed pod is jointed, tough or bony and breaks into single seeded segments.

Cultivated Radish has white to lilac pink or mauve flowers; the seed pod is spongy, lacks distinct constrictions and splits in various ways but not into single seeded segments. The taproot of Cultivated Radish is swollen and edible. In some varieties it is bright red.

References:

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Cheam, A.H. (1986). Seed production and seed dormancy in wild radish (Raphanus raphanistrum L.) and some possibilities for improving control. Weed Research 26: 405-13.

Cheam (1996) Toxicity of green wild radish pods on crop seeds. Agriculture WA, Farmnote 91/96.

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Acknowledgments:

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