Two introduced species of broomrape (Orobanche species) are found in Australia: branched broomrape (O. Ramosa) and clover broomrape (O. Minor). Clover broomrape has not been recorded as causing serious problems to date. Early action and good planning by property owners, backed up by on-going management, will help reduce the impact of broomrape.
- parasitic plant only found alongside a suitable broadleaf host plant
- the only visible part of the plant is the flowering shoot, it is leafless and yellow to buff coloured
- no part of the plant is green, the only leaves produced are a few small brownish scales
- branched broomrape has stems 5-20cm high, densely branched from the base, with a row of lavender-blue trumpet-shaped flowers protruding from the sides of the stem
- the other species have taller unbranched stems 15-60cm high, and dark mauve to dull cream flowers
- seeds are dust-sized and dark brown, each single capsule contains 600-800 seeds
- seeds have a rough surface that sticks to dry surfaces including the seeds of other plants.
Why is it a problem?
- has the potential to impact in terms of production losses and threats to export markets
- has a wide host range that includes horticultural crops, so there is potential for yield reduction due to direct parasitism
- several countries have import regulations prohibiting the presence of branched broomrape seed as a contaminant in produce, or its import as seed
- may affect the sale of high risk produce such as host rich hay or seed potatoes.
- Eyre Peninsula – one known infestation of O. Minor
- Northern pastoral – not known to be present
- Northern agricultural districts and Yorke Peninsula – scattered outbreaks of O. Minor
- Murray Mallee – large localised infestation of O. Ramosa near Murray Bridge
- Riverland area – small isolated patches of O. Minor
- South East – one record of O. Minor
- Central region – few small isolated infestations of O. Minor.
- seeds form a large seed bank in the soil, remaining viable for many years
- seeds germinate in response to chemicals secreted from the roots of plants and then seedling attaches to a host root
- after attachment, the parasite accumulates food reserves for 1 to 2 months, stems emerge in spring
- flowering begins within days of stem emergence and the seed can ripen within a week.
How it spreads
Seed is spread by:
- livestock – through the gut and on their feet
- farm machinery via soil (particularly in wet periods)
- contaminated fodder, seed, soil and sand
- wind dispersal, especially in a sand dune blowout (does not happen frequently).