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Bitou Bush

Bitou plant

Bitou new growth with white hairs

Bitou bush leaves & flower

Bitou flower & fruit

Bitou bush flower & fruits

Bitou seedling

Boneseed plant

Boneseed seedling

Boobialla fruit

Sea box flowers & fruit

Scaevola calendulacea

Scaevola calendulacea flowers & fruits

Bitou seedling (R) & Scaevola calendulacea

Senecio angulatus, climbing groundsel

Senecio angulatus, climbing groundsel 1

Senecio macroglossus, climbing groundsel



family

Asteraceae (daisies)

status

Weed of National Significance.

Bitou bush (Chrysanthemoides monilifera ssp rotundata) is declared noxious in all coastal Local Government Areas in either Class 3 (Bega Valley) or 4 (Eurobodalla, Shoalhaven and Illawarra LCAs). It is not declared in non-coastal LCAs in the ST and SE Region, as it is largely a coastal weed, as a result of an early policy of planting it on beaches for dune stabilisation. It cannot be propagated or sold anywhere in the state.

The South Coast Regional Bitou Bush Strategy (Broese & Wolfenden 2002) aims to eradicate bitou bush south from Sussex Inlet. All relevant regional land management authorities are involved in devising and implementing this strategy.
Invasion of native vegetation by bitou bush has been listed as a Key Threatening Process under the NSW Threatened Species Conservation Act 1995.

Description

Bitou bush is an evergreen shrub usually about 1-2 m high, but it can scramble several metres up into trees. Leaves are bright green, broadly oval, thick and fleshy, usually with a few small teeth along the margins near the tip. New growth is whitish with a covering of fine hairs. Yellow daisy flowers with 11-13 petals are followed by black fleshy fruits 6-8 mm in diameter, in small clusters. Each fruit contains one oval, ribbed seed 5-7mm long. Peak flowering is in autumn, but some flowering occurs all year.

Preferred habitat and impacts

Bitou bush usually occurs very close to the sea, on dunes, sea-cliffs and in forest on sandy soils. It was promoted for erosion control on coastal dunes in the 1950’s and 60’s. It will invade grassy or heathy headlands, coastal banksia scrub on dunes, dry eucalypt forest and littoral rainforest. It is not usually a weed of farming areas because it is eaten by livestock.
Bitou forms a dense cover which suppresses native shrubs and groundcover species and prevents tree regeneration. Plants which climb into small trees such as banksias can make these trees so top-heavy that they are blown over or snapped off in strong winds.
Bitou can produce seed within one year of germination, and seed production is prolific (up to 50,000 seeds per plant per year). Seeds can remain viable in the soil for up to 7 years, resulting in the accumulation of a massive soil seed bank. Germination is stimulated by fire or other disturbance, and after passing through a bird gut. The potential for native vegetation to be overwhelmed in areas where bitou occurs is very high.

Dispersal

Birds and other animals. Movement of seed-contaminated soil. The appearance of isolated plants on beaches distant from any known infestation suggests that bitou seed is spread by ocean currents.

Look-alikes

Boneseed (Chrysanthemoides monilifera ssp monilifera) is similar in flowers and fruits, but leaves have a pointed tip and the leaf margins are more toothed. It is usually a garden escapee found close to houses, and may occur in forest or occasionally coastal dunes if planted nearby. 

Similar natives found in coastal habitats are boobialla (Myoporum boninense),  sea box (Alyxia buxifolia) and the low, sprawling shrub Scaevola calendulacea. The first two grow mostly on sea cliffs, but sometimes on dunes, and have round or fleshy leaves. Boobialla is the most similar, with fleshy bright green leaves, white shortly tubular flowers spotted purple inside and succulent purple fruits. Sea box has round leathery leaves, white flowers and red berries.

Scaevola calendulacea can grow on dunes or less commonly, cliffs and has pale blue to mauve flowers followed by purple berries.  Its leaves are fleshy, bright green, with a rounded tip and can be very similar to bitou bush leaves, especially on plants growing in a sheltered situation.


A weed with similar fleshy leaves is the shrubby climber, climbing groundsel (Senecio angulatus), but its leaves are bluntly angular, not rounded. It also has yellow daisy flowers, but the seeds are more typical daisy seeds with a parachute of hairs, like those of dandelions. Another similar but less common climber is Senecio macroglossus, which has leaves with sharply pointed lobes, and large, paler yellow flowers than Senecio angulatus.

Control

For large bitou bush plants growing amongst native vegetation, use cut and paint to minimise impacts on native vegetation. Scattered seedlings and smaller plants can be hand-pulled or dug out. Even quite large plants pull up quite easily in sandy soils.  Spraying with glyphosate (eg Round Up) or metsulfuron (eg Brush Off) is used for dense infestations. Over-spraying with a low concentration of glyphosate in winter can kill bitou without affecting native vegetation. The splattergun method of herbicide application has proven successful with bitou bush.  This applies small quantities of more concentrated herbicide to the foliage using a larger droplet size and if carefully done, creates less damage from spray drift onto nearby native vegetation.
A hot fire can be used to kill mature plants, kill shallowly buried seed and stimulate germination of most deeper seed, after which seedlings can be sprayed. Burning may be appropriate in forests, but should not be used on dunes, where it could promote erosion. Fire should not be used unless the resources are available for follow-up control of new bitou seedlings, and other weeds which may also invade. Burning after spraying can be useful in removing dead material to provide easier access for follow-up work.


Three biological control agents from bitou’s home territory of South Africa have been released on the south coast in recent years. Bitou Tip Moth destroys the growing tips, but has not proven very effective south of Sydney. Bitou Seed Fly destroys about 30% of the annual seed crop, but given the size of the seed crop, this is not really a significant gain. Caterpillars of the Leaf Rolling Moth eat the growing tips of the plant, but predation by native spiders and insects has prevented its population from building up as rapidly as was hoped. The search goes on for more suitable South African insects and fungi that could be used.


Where bitou is growing among native vegetation, as it usually does, natural regeneration will generally follow bitou removal without the need for planting. However, sensitive sites such as dunes may need planting with appropriate local natives to hasten the process and minimise the short-term risk of erosion