Branched Broomrape

Orobanche ramosa

Family: Orobanchaceae.

Names:

Orobanche is from the Greek orobos meaning vetch and ankhein meaning to strangle referring to its parasitism on vetches and legumes.
Ramosa
Branched Broomrape because the stems are branched and Broomrape comes from Broom, a leguminous plant, which it often parasitises or rapes.

Other Names:

Summary:

A light brown, annual, erect root parasite with multiple stems branching from the base. It has scale like leaves and pale blue to purplish flowers from October to December. It is not green at any stage.

Description:

Cotyledons:

Two.

Leaves:

Alternate. Tiny, brown and scale like.
Stipules - None.

Stems:

Flower stem - Brown, erect, branched at the base above ground, 50-300 mm tall.

Flower head:

Terminal raceme or spike with bracts. Cylindrical with many tubular flowers.

Flowers:

White to pale blue, tubular, bisexual, 2 lipped.
Ovary - Superior, 4 placentas, many ovules. Slender style. Flat topped stigma.
Sepals - Tubular to bell shaped, 4 or 5 toothed or 2 side sepals that are 1 or 2 lobed. Usually with tiny bracts attached to the base.
Petals - Tubular, erect or curved, 2 lipped. Upper lip equal to or shorter than the lower lip. Upper lip notched or 2 lobed. Lower lip 3 lobed.
Stamens - Attached inside the petal tube, 4 fertile plus 1 infertile stamen (staminode).
Anthers - 2 celled, opening by a longitudinal slit, 2 valves.

Fruit:

Capsule, releases seed through slits.

Seeds:

Many, brown, tiny and dust like. Up to 500,000 per plant.

Roots:

Thick, fleshy and attached to host plant.

Key Characters:

Multiple stems branching from the base above ground level.
Alternate, scale like leaves.
Pale blue to purplish flowers from October to December.
No chlorophyll and not green at any stage

Biology:

Life cycle:

Annual. Seeds germinate in autumn and it grows completely underground attached to the roots of the host plant for about 6 weeks before it sends up a flowering stem, less than 300 mm tall, in late spring to early summer. It can flower and set seed within 2 weeks of the flowering stem emerging. It then browns off with the onset of summer drought.

Physiology:

Reproduction:

By seed.

Flowering times:

Late spring to early summer.

Seed Biology and Germination:

Seed may remain dormant for up to 15 years.
Requires a host close by to initiate germination.

Vegetative Propagules:

None.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread in produce and by machinery and stock.
Each plant can produce up to 500,000 seeds.

Habitats:

Climate:

Temperate.

Soil:

Seems to prefer free draining alkaline soils with low nitrogen levels.

Plant Associations:

Major parasite of Canola, Faba Beans, Field Peas, Lentils, Medics and Sunflowers.
It is a parasite of many other broad-leaved plants including clovers and legumes.
It does not parasitise cereals but can live on broad-leaved weeds in the crop and contaminate the grain.

Origin and History:

First found in the South Australian Mallee in 1992 and was the subject of an eradication campaign.

Distribution:

SA. About 33,000 ha is infested at low levels.

Courtesy Australia's Virtual Herbarium.

Significance:

Infests 16 million hectares of crops worldwide.
Many countries will not buy produce that is from Branched Broomrape areas or is thought to be contaminated with its seed.

Beneficial:

Ornamental.

Detrimental:

Weed of clover and legume pastures and crops.
In SA it has been found on Canola, Field Pea and Medic crops; Capeweed, Cretan Weed, Long-fruited Turnip, Skeleton Weed, Stemless Thistle and Tolpis weeds; and Poached Egg Daisy, Variable Daisy and Variable Groundsel native plants.
Grain yields of Canola have been reduced by up to 75% and Chickpea yields by up to 50% in heavy infestations.
The seed is prohibited in produce exported to many countries.

Toxicity:

Not recorded as toxic.

Legislation:

Noxious weed.

Management and Control:

Report infestations to the State Department of Agriculture to obtain a control and containment program.
Plant infested areas to cereals and treat with Group B herbicides.
Control broad-leaved species.
Wash down vehicles and equipment before leaving infested areas.

Thresholds:

Eradication strategies:

Remove hosts.
Spray with low rates of glyphosate or Spinnaker.
Group B herbicides also provide control.

Herbicide resistance:

Biological Control:

Related plants:

Australian Broomrape (Orobanche cernua var. australiana) is found in association with Senecio spp.
Lesser Broomrape (Orobanche minor) is found in association with legumes and other broadleaf species.
Crenate Broomrape (Orobanche crenata) has yellow flowers and found in association with legume and vegetable crops and has not been found in Australia.
Egyptian Broomrape (Orobanche aegyptiaca) has blue to purple flowers and is found on Canola, Brassica or Cole crops and other vegetables and has not been found in Australia.
Nodding Broomrape (Orobanche cernua var. cernua) is found on carrots, Lathyrus and vegetables and has not been found in Australia.
Orobanche papaveris is found in association with poppies.

Plants of similar appearance:

References:

Top Crop P103.

P. Jupp 1999 Pers Comm.

Philip Warren. PIRSA.

Anon (2000). Farmer Alert (2000). Keep your markets safe. Department of Agriculture Fisheries and Forestry.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.