Emerging plant pests - South African citrus thrips
Officers of Biosecurity
Fig 1 Magnified larvae and single adult
of South African citrus thrips
Fig 2 Mother of millions plant, a common
host of South African citrus thrips
Acknowledgment: figure 1 courtesy of Citrus
Research International, South Africa.
South African citrus thrips (Scirtothrips aurantii Faure) (SACT) was detected at Sherwood in Brisbane in March 2002, feeding on mother of millions, a succulent weed belonging to the family Crassulaceae. This was the first record of this thrips in Australia.
To date, SACT has only been found on these weeds and has not been recorded on fruiting crops such as citrus. There is some speculation that the biotype of SACT that occurs in Australia is slightly different from the overseas pest biotype and that it could have a preference for feeding on Crassulaceae weeds.
Since the first detection of SACT, an intensive surveillance program has found it over a relatively wide area of southwest Brisbane, indicating that the pest is well established.
Overseas information shows that SACT feeds on a wide variety of ornamental and fruit crops, but is known to be particularly damaging to citrus. On citrus, SACT feeds on fruit and young leaves causing leaf drop and fruit distortion, leading to a reduction in marketable yield. It is widespread in Africa and has also been detected in Yemen, Mauritius, Reunion and Cape Verde. It is an important pest in low altitude dry parts of South Africa and Zimbabwe. Significant parts of Queensland and interstate would most likely contain suitable habitats for its establishment.
What does it look like?
South African citrus thrips adults are tiny (less than 1mm) pale yellow-orange insects (see Figure 1). On citrus they prefer to feed in young growing tips and on young fruit. Brown scarring on the surface of fruit, leaves or stems could indicate their presence. The tips of injured leaves often curl or roll inward around the midrib like a rat's tail, forming a groove in which the insect feeds. Heavily infested leaves may be stunted in growth and deformed. Damage on citrus fruit is characterised by a ring of brown scarring on the stem end. Young shoots may turn black and fall off.
SACT can build up to damaging levels during prolonged periods of hot, dry conditions, but will become scarce after periods of heavy rainfall and/or cool weather.
How does it spread?
Like other thrips, SACT can easily spread to other locations on wind currents, infested plant material and on almost any surface they come into contact with, including clothing. As SACT requires access to soft green tissues; nymphs and adults are normally found only on seedlings or cuttings with young growing leaf buds. Similarly mature harvested fruits are unlikely to carry SACT, because it only attacks immature fruit.
Further information
If you would like further information or think that you may have seen South
African citrus thrips, contact your nearest DPI&F plant health inspector or the
DPI&F Customer Service Centre on 13 25 23 (free call for Queensland residents;
8 a.m. to 6 p.m. weekdays) for advice on what to do next. Non-Queensland residents:
phone 07 3404 6999. E-mail the DPI&F Customer Service Centre: callweb@dpi.qld.gov.au. DPI&F Internet site: www.dpi.qld.gov.au.
This DPI Note is also published on the DPI's PrimeNotes CD-ROM.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last reviewed 31 May 2005