Takagi, 1977
Diagnosis
In life, scale cover of adult female broadly mussel-shaped to oval (often distorted due to overcrowing), convex, slightly translucent, white to pale buff, with pale buff terminal exuviae. Scale cover of male smaller than that of female, elongate, parallel-sided, white and tricarinate with pale buff terminal exuviae. AULYASL3.jpg
Slide-mounted adult female with swollen, more or less rounded cephalothorax; gland spines and macroducts absent from thorax and head AUYAS.jpg . Pygidium with median lobes zygotic, without any setae or gland spines between their bases; abdominal segment VI bearing one or two submedian macroducts on each side; pore prominences between pygidial lobes short AUYAP1.jpg
AUYAP2.jpg . Feeds only on cycads.
Host range
Aulacaspis yasumatsui has a restricted host range, feeding on members of three families of cycads: Cycadaceae, Zamiaceae and Stangeriaceae (Howard et al., 1999). Hosts include species of: Cycas spp., Cycas revoluta, Dioon, Encephalartos, Macrozamia, Microcycas and Stangeria.
Affected plant stages: vegetative growing, flowering and fruiting stages
Affected plant parts: mainly undersides of pinnae AULYASL2.jpg , but in heavy infestations all the aerial parts become infested AULYASL1.jpg , and sometimes even the roots AULYASL4.jpg
Biology and ecology
Reproduction is sexual. In tropical conditions, A. yasumatsui breeds continuously; development from egg to egg-laying female takes about 28 days at 25°C; and each adult female can lay more than 100 eggs, which hatch in 8-12 days at 24.5°C (Howard et al., 1999).
Howard et al., 1999, suggested that A. yasumatsui prefered climates in which there is a pronounced dry season; this may partly explain why the scale is not a serious problem in Singapore (Hodgson and Martin, 2001).
Crawlers are the primary dispersal stage and move to new areas of the plant or are dispersed by wind or animal contact. Mortality due to abiotic factors is high in this stage. Dispersal of sessile adults and eggs occurs through human transport of infested plant material.
Symptoms
Infestation of cycads by A. yasumatsui causes chlorosis and severe dieback AULYASL5.jpg , and often kills the plant in only a few months (CABI, 2000a). From a distance, heavy infestations give the plant an appearance of being coated with mildew because of the encrustations of white scale covers (Hodgson and Martin, 2001).
Economic impact
Cycads are very expensive ornamental plants because they grow so slowly; therefore A. yasumatsui has had a considerable impact on the horticultural industry and amenity plantings in countries where it has been introduced without any natural enemies. For example, in Hong Kong it causes 70-100% mortality of ornamental cycads (Hodgson and Martin, 2001), and it has had a serious impact on botanical gardens in Florida (Howard et al., 1999). However, where hymenopterous parasitoids are present, its impact is greatly reduced, e.g. in Singapore, Thailand and now in Florida (Howard and Weissling, 1999; Hodgson and Martin, 2001).
Phytosanitary risk
This species is increasing its range though transport of infected ornamental cycads (especially Cycas revoluta). It was intercepted at plant quarantine in France in 2000 (Germain, 2002). Shipment of these large plants creates a considerable risk that A. yasumatsui will continue to spread to more tropical countries. Such plants should be inspected thoroughly at import.
Detection and inspection methods
This insect can spread between countries by the transport of cycad trees that are infested. The undersides of the leaves should be thoroughly inspected for white encrustations of scale covers, using additional light if necessary. From a distance, heavy infestation gives the plant an appearance of being coated with mildew because of the encrustations of white scale covers (Hodgson and Martin, 2001).
Phytosanitary risk and regulation
This species is increasing its range though transport of infected ornamental cycads (especially Cycas revoluta); it was intercepted at plant quarantine in France in 2000 (Germain, 2002).
Natural enemies
The natural enemies of A. yasumatsui have been little studied so far.
Parasitoids:
- Coccobius fulvus, in Thailand: introduced to USA (Florida)
- ?Encarsia sp., in Thailand (A. Polaszek, pers. comm.)
Predators:
- Cybocephalus binotatus, in Thailand: introduced to USA (Florida)
Distribution
See Aulacaspis yasumatsui distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
The narrow form of A. machili (Takahashi) is very similar to A. yasumatsui, but differs in lacking dorsal microducts on abdominal segments I and II; these ducts are present in A. yasumatsui AUYAS.jpg. The species can also be distinguished by their different host preferences. Unlike A. yasumatsui, which feeds on cycads, A. machili has been recorded on Persea (previously Machilus) japonica (Lauraceae) in Taiwan and Persea (previously Machilus) thunbergi in Japan (Honshu, Ryukyu) (Takahashi, 1931; 1970 and 1998 data from S. Kawai photographs). AULMACL1.jpg , AULMACL2.jpg
Comments
Aulacaspis yasumatsui is probably native to a region of South-east Asia around Thailand. It was first collected outside Thailand in Hong Kong in 1992 and has spread to several other countries since, due to trade in infested ornamental cycads. It is probably still expanding its geographical range, and has not yet been recorded in Europe, Africa, Australia, or from the Pacific islands (apart from Hawaii).
Asia
China
Guangdong: present, no further details (Tao, 1999)
Hong Kong: present, no further details (CABI, 2000a; Hodgson and Martin, 2001)
Southern China: present, no further details (Howard and Weissling, 1999; Heu and Chun, 2000)
Singapore: present, no further details (Hodgson and Martin, 2001)
Thailand: present, no further details (Takagi, 1977; Tao, 1999; CABI, 2000a)
Western Hemisphere
Bahamas: collected from New Providence (The Natural History Museum collection, London, UK)
Cayman Is: present, no further details ( Howard and Weissling, 1999; CABI, 2000a)
Puerto Rico: present, no further details (Halbert, 2000; CABI, 2000a)
USA
Florida: present, no further details (Howard et al., 1999; CABI, 2000a)
Hawaii: present on Oahu and Hawaii (Hodgson and Martin, 2001; Heu, 2002)
Southern USA: present, no further details (Howard et al., 1999; Howard and Weissling, 1999)
US Virgin Is: present, no further details ( Howard and Weissling, 1999; CABI, 2000a)