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Silverleaf Whitefly Silverleaf whitefly April 2015 Primefact 1400 First edition Plant Biosecurity & Product Integrity, Orange There are two known biotypes of silverleaf whitefly (Bemisia tabaci) present in Australia. Exotic biotypes of silverleaf whitefly present overseas and not present in Australia differ from Australian strains by ● attacking different host plants ● responding differently to insecticides ● their ability to transmit exotic diseases Silverleaf whitefly Figure 1 Silverleaf whitefly adult (approx. 1 mm) Silverleaf whitefly (SLW), also known as sweet potato, cotton, tobacco or poinsettia whitefly, is a sap sucking insect. As its multiple names suggest, SLW feeds on and is able to transmit viruses across a very wide variety of host plants. Silverleaf whitefly feeds on the undersides of leaves and when present in large numbers can significantly impact plant health. In crop plants, this leads to reduced yield and quality of produce. The SLW species can be broken down to a number of ‘biotypes’. The species is currently represented in Australia by Australian native and Figure 2 Silverleaf whiteflies coated in white B biotypes. Other biotypes present overseas can powdery wax on the underside of a leaf pose a threat to Australia’s biosecurity by differing in host range, resistance to insecticides Wings generally do not meet over the back but or ability to transmit diseases. have a small space separating them (Figure 1). Indicators that a new biotype of SLW may have Adults coat their wings with a powdery wax, been introduced to Australia include poor control colouring them an opaque, iridescent white response with regular insecticides or unusual (Figure 2). symptoms accompanying infestations that could indicate the presence of a new, exotic disease. Immature stages Silverleaf whitefly nymphs are oval and scale-like Description in appearance. They develop from whitish green in colour to greenish yellow as they go through Adults growth stages. Older stage nymphs develop The body of adult SLW is about 1 mm long and prominent red eyes. Eggs are oval shaped and coloured light yellow. Wings are held tent-like pearly white but difficult to detect with the naked over the body. eye. Silverleaf whitefly Damage Spread Yellow spotting of leaves caused by SLW feeding Ease of dispersal of SLW has already been is an early sign of infestation. As SLW numbers demonstrated by its introduction to all continents. increase, yellowing intensifies to cause whole leaf Long distance dispersal occurs by plant material yellowing and eventual leaf drop. At high carrying eggs and nymphs. numbers, SLW can retard plant growth. Adults spread short distances by flying. Adults do Nymphs cause toxic reactions in many host not fly very efficiently but can be transported long plants when they feed. Reactions vary depending distances by strong wind currents. on plant species but generally lead to disorders such as distorted growth of fruit, fruit bleaching, irregular ripening, leaf streaking, silvering, Management yellowing and blanching. There are multiple cultural, chemical and Growth of sooty mould encouraged by honeydew biological methods of control that can be applied secretion, and loss of leaves due to feeding to manage SLW and the viruses it carries. damage reduces the plant’s exposure to sunlight. Methods include: This can lead to reduced vigour, stunting, loss of insecticides yield and poor quality. intercropping with non-hosts Silverleaf whitefly can transmit over 60 plant coloured or reflective mulches viruses. Symptoms of virus infection are variable but can also indicate the presence of SLW. control of alternative weed hosts that may harbour whitefly transmitted viruses Lifecycle natural parasites, predators and pathogens Eggs of unmated SLW females will hatch only If you suspect an exotic biotype male offspring. Mated females can produce both male and female offspring. Females lay eggs If you suspect an exotic biotype of SLW while feeding on the underside of leaves in a Call the Exotic Plant Pest Hotline on semi-circular arrangement around the feeding 1800 084 881 site. They can lay up to 300 eggs in their lifetime. Take photos not samples to minimise the risk Nymphs go through four instar (growth) stages, of spreading this pest each lasting around 3−5 days, before reaching adulthood. Email clear photos with a brief explanation and contact details to Adult females will live and continuously mate for [email protected] 10−25 days. The life of the male is much shorter. Up to 15 generations can occur within one year. In cooler temperatures SLW will overwinter on A plant pest is a disease causing organism or an alternative hosts and weeds. As temperatures invertebrate which threatens agricultural warm up, numbers rapidly increase, with the production, forestry or native and amenity plants. highest numbers occurring in mid to late summer. Acknowledgments Host range Figure 1 courtesy of Lesley Ingram, Bugwood.org The host range of SLW varies with different Figure 2 courtesy of W. Billen, Pflanzenbeschaustelle, biotypes. The highly invasive B biotype, present Weil am Rhein, Bugwood.org worldwide, is estimated to have a host range of around 600 plant species. This includes a © State of New South Wales through the Department of Trade and number of crop and ornamental plants worldwide. Investment, Regional Infrastructure and Services 2015. You may copy, distribute and otherwise freely deal with this publication for any purpose, provided that you attribute the NSW Department of Primary Silverleaf whitefly in Australia Industries as the owner. Disclaimer: The information contained in this publication is based on Silverleaf whitefly biotypes are frequently being knowledge and understanding at the time of writing (May 2015). reviewed by scientists. Differences between However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date biotypes of SLW are determined by molecular and to check currency of the information with the appropriate officer of means. the Department of Primary Industries or the user’s independent adviser. There are a number of biotypes present overseas Published by the NSW Department of Primary Industries. that are not established in Australia. PUB15/133 2 NSW Department of Primary Industries, May 2015 .
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