| Scientific name | Annona glabra |
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| Description |
- Semi-deciduous tree that grows to 3 to 6m in height and can reach up to 15m.
- Softwood stems with a thin grey bark bearing prominent lenticels (pores that allow gas exchange)
- Leaves are alternate, 7 to 12cm long with a prominent midrib.
- Leaves vary from light to dark green.
- When crushed, leaves emit a distinct smell similar to green apples.
- Flowers are pale yellow to cream with red inner-base that consist of three leathery outer petals and three smaller inner petals.
- Flowers are short-lived, rarely noticed and 2 to 3cm in diameter.
- Green spherical fruit about 5 to 15cm in diameter, which looks like a smooth-skinned custard apple.
- Each fruit contains 100 to 200 seeds of similar size and shape to pumpkin seed.
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| Habitat |
- Requires moist soil with regular inundations of fresh to brackish water.
- Prefers creeks, riverbanks, floodplains, wetlands, rainforest areas and agricultural drainage systems.
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| Distribution |
- Native of tropical North, Central and South America.
- Covers around 2200ha of Queensland, with the main infestation in the Wet Tropics bioregion between Cardwell and Cooktown.
- Small and/or isolated infestations are found in Brisbane, Nambour, Mackay, Townsville, Ingham, the east coast of Cape York and the Torres Strait Islands.
- An infestation was discovered south of Darwin in late 2010.
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| Life cycle |
- Flowers and produces fruit when at least two years old.
- Main flowering period in the Wet Tropics is from December to February with fruit formation following in January to March.
- Sporadic flowering and fruiting can also occur at other times of the year.
- Both fruit and seed can float and remain viable for many months in fresh to saline water and germination can occur in fresh or brackish situations.
- Seeds are relatively short-lived and when conditions are suitable, seed banks can be rapidly depleted through mass germinations within six months of fruit fall.
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| Spread | Generally spread by water, seed can also be disseminated by feral pigs, wallabies, cassowaries and other fruit-eating animals. |
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| Impacts |
Environmental:
- Invades fresh, brackish and saltwater areas.
- Forms dense stands in swamp areas, thickets capable of replacing ecosystems.
- Ability to colonise undisturbed areas.
- Melaleuca wetlands, Heritiera littoralis mangrove communities, riparian areas, drainage lines, coastal dunes and islands are most at risk.
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| Prevention |
The best form of weed control is prevention. Treat weed infestations when they are small. Do not allow weeds to establish.
Steps for weed prevention:
- Check your property regularly for suspect plants.
- Control new infestations before they spread and become a major problem.
- Don't dump weeds and garden waste in bush or parkland.
- Know the weed status of any products or materials you are receiving. This includes fodder, grain, gravel, machinery, mulch, packing material, sand, soil, stock, vehicles and water.
- Clean your equipment, clothing, shoes, vehicles and machinery when leaving natural habitats and camping areas.
- Use a cleandown facility to blow, vacuum or wash dirt and seeds from vehicles, machinery and tools.
- Request a weed hygiene declaration from your suppliers.
- Ensure vehicles and machinery are clean before entering your property.
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| Physical control |
Hand-pulling is effective.
Fire:
- Sufficient fuel is required for control using fire. Unfortunately this is not often available in dense pond apple infestations.
- Entire circumference of the plant must be burnt to kill effectively. Depending on its intensity, a fire can destroy seeds lying on the ground but seeds in cracks or on moist soil where fire will not burn can remain viable.
- Follow-up work is required to control seedlings that germinate following fire.
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| Mechanical control |
- Options include chain pulling and dozer pushing.
- These methods (except hand pulling) are only suitable on flat country; in areas free of sensitive vegetation; where machines can manoeuvre easily; and where the risk of soil erosion is low.
- Ensure that the roots of uprooted trees are not in contact with soil or else plants may resprout.
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| Herbicide control |
Stem injection:
- Recommended for aquatic areas as it minimises herbicide run-off and off-target impacts.
- Stem injection is not generally suited to larger trees due to the number of cuts/holes required. It is also difficult to control multi-stemmed trees where each separate stem requires treatment.
Axe cut method:
- Make horizontal cuts into the sapwood around the circumference of the stem, as low to the ground as possible.
- While still in the cut, lean the axe out to make a downward angled pocket in which herbicide is injected. A double row of cuts, with the second row placed under the spaces created by the first row, is recommended for maximum kill rate.
'Drill and fill method':
- Drill downward angled holes, 5cm apart around the circumference, with a powered drill. Herbicide is then immediately injected into the holes.
Cut stump:
- Suitable for use on large trees and multi-stemmed plants.
- Cut stem through horizontally, as close to the ground as possible, and the cut surface is treated immediately with herbicide.
Basal bark:
- Spray or paint herbicide and diesel mix around the circumference of the stem, from ground level up to 50cm.
- Do not use in aquatic situations for both environmental and effectiveness reasons.
Foliar application:
- Herbicides are useful for dense monocultures of young plants up to 1m tall where there is no risk of damaging native vegetation.
- See the pond apple fact sheet (PDF, 218 KB) for herbicide control and application rates.
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| Biological control | There is no biological control agent available for pond apple. |
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| Declaration details |
- A declared Class 2 species under the Land Protection (Pest and Stock Route Management) Act 2002.
- Taking for commercial use, introduction, keeping, releasing and supplying (including supplying things containing reproductive material of this pest) is prohibited without a permit issued by Biosecurity Queensland.
- Landholders are required to control declared pests on their properties.
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