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Asian cycad scale

Asian cycad scale (Aulacaspis yasumatsui) is a sap-sucking bug from Thailand that has driven cycads close to extinction on Guam and Taiwan after travelling widely on cultivated cycads.

These slender scales are mainly males. Photo: F.W. Howard, University of Florida, Bugwood.org

Identification

The cycad scale is a tiny, orange, sap-sucking bug that lives under a white or translucent shelter (scale) it constructs from anal secretions to protect it from weather and enemies. The scales of females are less than 2 millimetres long and highly variable in form. They tend to be pear-shaped but can be circular, oblong, or irregular in shape when scales are crowded together. They often remained attached to the cycad surface, even after the bug has died. The scales of male are long and narrow and smaller. They have a grooved surface.

The underside of this frond shows a scatter of female scales alongside the much smaller males. Photo: John A. Davidson, Univ. Md, College Pk, Bugwood.org

This species is very difficult to distinguish from similar scales, and it is their dense white infestations that should be looked for, in combination with sick and dying cycads. They should be looked for on cultivated cycads, and on wild cycads growing near houses.   

The sago palm (Cycas revoluta), more properly called the sago cycad, is often grown in Australian parks and gardens and is highly susceptible. Plants under early attack reveal their plight by first showing small yellow spots on the upper surface of their fronds. As the infestation progresses fronds turn yellowish then brown and dry. 

This cycad has brown dessicated fronds, a withering green frond, and frond stalks densely coated in cycad scales. Photo: F.W. Howard, University of Florida, Bugwood.org

This cycad is dying from scale attack. Photo: Florida Division of Plant Industry, Bugwood.org

Those who aren’t familiar with cycads may confuse them with young palms, since both have fronds. The leathery leaves of cycads are much thicker and stiffer than those of palms. The trunks are very thick for the height of the plant. Many cycads, including sago palm, have fronds on which each leaflet ends in a spine. Its leaflets are rigid and only about 4 millimetres wide.

Sago palms can suffer dieback on the tips of their leaflets, which can turn whitish, but this looks very different from scale attack, which is not directed at leaf tips.

A female scale can be seen here beneath her semi-transparent cover. Beside her are two male scales. Photo: Jeffrey W Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org | CC BY 3.0

Size

Females are 1.2-1.6 millimetres long. Males are only 0.5 to 0.6 millimetres long.

Behaviour and location

The scales at first congregate mainly on the undersides of fronds, but when they reach extreme numbers they attach to the stalks of fronds, the cones and seeds, to upper frond surfaces and to roots up to 60 centimetres underground. Heavy infestations lead to multiple layers of live and dead scales forming a waxy white ‘crust’ on the frond surface at densities of hundreds per square centimetre. A cycad can end up looking like it is dusted in snow. It may die within months or even weeks of the first scale arriving.

Similar species

The false oleander scale (Pseudaulacaspis cockerelli) and hibiscus snow scale (Pinnaspis strachani) sometimes feed on cycads, though they are not cycad specialists and do not reach extreme numbers. The false oleander scale is more likely to feed on the upper side of fronds than beneath them. It is yellow rather than orange but the difference in colour is not pronounced and not a reliable way to distinguish the two

This scale likes a subtropical or tropical climate and is unlikely to do well south of Sydney.

Who to tell

Think you’ve found Asian cycad scale?

If you find them phone 1800 900 090 and ask for the office of Australia’s Chief Environmental Biosecurity Officer. Contact us as well via our online form.

The problem

This sap-sucking scale has caused mass deaths of wild and cultivated cycads since it spread around the world from its native Thailand with the cycad trade. Cycad species in Taiwan and Guam are now endangered following its arrival. It multiplies so rapidly, achieving dense populations, it can kill a cycad grove within a year of arriving. The IUCN considers it the ‘single most important threat to natural cycad populations’.

The Australian government foolishly allows the importation of fresh cycad foliage for sale in floral arrangements, and the scale could enter on these. It has been intercepted in many countries on imported cycads or cycad foliage, including New Zealand.

Australia is a global centre for native cycads, with 70 species, the vast majority of which have such small distributions they are inherently vulnerable to any new enemy. Australia has 28 species of Cycas, the main genus afflicted by the scale overseas. The country has 38 species of Macrozamia, a genus confined to Australia that is sometimes cultivated abroad, hence an overseas report that a southern Queensland species, M. lucida, is particularly susceptible to the scale. Australia has two species of Bowenia and this genus is also susceptible. Some of Australia’s cycads grow in places that could be too dry for the bug, or too remote for it to reach, but large numbers of species should be considered vulnerable, including some that are already listed as endangered, such as M. lomandroides.

Cycads are such popular garden plants that the scale is a major concern for horticulture as well. The main cycad cultivated in Australia, the sago palm, is often killed by the scale in gardens overseas. One nursery in Taiwan lost 100 000 sago palms in a year.

Further Information

The Global Invasive Species Database has a page on this species that includes (at the top) graphic images of its environmental impacts:

Who to tell

Think you’ve found Asian cycad scale?

If you find them phone 1800 900 090 and ask for the office of Australia’s Chief Environmental Biosecurity Officer.

Contact us as well via our online form.

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Dear Project Team,

[YOUR PERSONALISED MESSAGE WILL APPEAR HERE.] 

I support the amendment to the Kosciuszko National Park Wild Horse Heritage Management Plan to allow our incredible National Parks staff to use aerial shooting as one method to rapidly reduce feral horse numbers. I want to see feral horse numbers urgently reduced in order to save the national park and our native wildlife that live there.

The current approach is not solving the problem. Feral horse numbers have rapidly increased in Kosciuszko National Park to around 18,000, a 30% jump in just the past 2 years. With the population so high, thousands of feral horses need to be removed annually to reduce numbers and stop our National Park becoming a horse paddock. Aerial shooting, undertaken humanely and safely by professionals using standard protocols, is the only way this can happen.

The government’s own management plan for feral horses states that ‘if undertaken in accordance with best practice, aerial shooting can have the lowest negative animal welfare impacts of all lethal control methods’.

This humane and effective practice is already used across Australia to manage hundreds of thousands of feral animals like horses, deer, pigs, and goats.

Trapping and rehoming of feral horses has been used in Kosciuszko National Park for well over a decade but has consistently failed to reduce the population, has delayed meaningful action and is expensive. There are too many feral horses in the Alps and not enough demand for rehoming for it to be relied upon for the reduction of the population.

Fertility control as a management tool is only effective for a small, geographically isolated, and accessible population of feral horses where the management outcome sought is to maintain the population at its current size. It is not a viable option to reduce the large and growing feral horse population in the vast and rugged terrain of Kosciuszko National Park.

Feral horses are trashing and trampling our sensitive alpine ecosystems and streams, causing the decline and extinction of native animals. The federal government’s Threatened Species Scientific Committee has stated that feral horses ‘may be the crucial factor that causes final extinction’ for 12 alpine species.

I recognise the sad reality that urgent and humane measures are necessary to urgently remove the horses or they will destroy the Snowies and the native wildlife that call the mountains home. I support a healthy national park where native species like the Corroboree Frog and Mountain Pygmy Possum can thrive.

Kind regards,
[Your name]
[Your email address]
[Your postcode]


Dear Project Team,

[YOUR PERSONALISED MESSAGE WILL APPEAR HERE.] 

I support the amendment to the Kosciuszko National Park Wild Horse Heritage Management Plan to allow our incredible National Parks staff to use aerial shooting as one method to rapidly reduce feral horse numbers. I want to see feral horse numbers urgently reduced in order to save the national park and our native wildlife that live there.

The current approach is not solving the problem. Feral horse numbers have rapidly increased in Kosciuszko National Park to around 18,000, a 30% jump in just the past 2 years. With the population so high, thousands of feral horses need to be removed annually to reduce numbers and stop our National Park becoming a horse paddock. Aerial shooting, undertaken humanely and safely by professionals using standard protocols, is the only way this can happen.

The government’s own management plan for feral horses states that ‘if undertaken in accordance with best practice, aerial shooting can have the lowest negative animal welfare impacts of all lethal control methods’.

This humane and effective practice is already used across Australia to manage hundreds of thousands of feral animals like horses, deer, pigs, and goats.

Trapping and rehoming of feral horses has been used in Kosciuszko National Park for well over a decade but has consistently failed to reduce the population, has delayed meaningful action and is expensive. There are too many feral horses in the Alps and not enough demand for rehoming for it to be relied upon for the reduction of the population.

Fertility control as a management tool is only effective for a small, geographically isolated, and accessible population of feral horses where the management outcome sought is to maintain the population at its current size. It is not a viable option to reduce the large and growing feral horse population in the vast and rugged terrain of Kosciuszko National Park.

Feral horses are trashing and trampling our sensitive alpine ecosystems and streams, causing the decline and extinction of native animals. The federal government’s Threatened Species Scientific Committee has stated that feral horses ‘may be the crucial factor that causes final extinction’ for 12 alpine species.

I recognise the sad reality that urgent and humane measures are necessary to urgently remove the horses or they will destroy the Snowies and the native wildlife that call the mountains home. I support a healthy national park where native species like the Corroboree Frog and Mountain Pygmy Possum can thrive.

Kind regards,
[Your name]
[Your email address]
[Your postcode]