Blink and you'll miss it: identifying branched broomrape
BRANCHED BROOMRAPE (Orobanche ramosa) is a small, nondescript brown or straw-coloured plant.
It is also one of the world's most feared weeds of broadleafed grain and horticultural crops. The plant has a wide host range, causes significant yield losses and is very difficult to control.
Worldwide, broomrape species infest 16 million hectares of crop land, with major hosts including sunflowers, faba beans and lentils.
Branched broomrape is an annual root parasite which extracts all its nutrients from host plants. These include a wide range of annual broadleafed crops and pastures, with canola, field peas and medic of particular concern. It also attacks a variety of broadleafed weeds and native plants.
The zone of weed infestation in SA is about 32,850 ha, including about 22 km of road verges. The weed is present in a small part of the SA Mallee east of Adelaide. Several properties wi th infested paddocks have been quarantined to protect the interests of farmers throughout Australia.
Branched broom rape spends most of its life underground and contains no chlorophyll. Consequently even newly emerged plants are brown or strawcoloured.
Plants emerge in late spring or early summer and grow to no more than 30 cm in height. The short-lived plants produce pale blue tubular flowers and set seed within two weeks of emergence. Each plant can produce up to 500,000 minute, dust-like seeds.
Other species of broomrape in Australia are not serious pests of crops. There are also broomrapes not yet found in Australia that are serious pests of crops in many other parts of the world.