Tomato leaf curl virus

Officers of DPI&F and the Northern Territory Department of Business, Industry and Resource Development.

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Introduction

Tomato leaf curl virus belongs to a group of viruses which are the cause of a range of destructive plant diseases world wide. These viruses are constantly evolving and threaten horticulture in many tropical and subtropical regions world wide. Tomato leaf curl virus (TLCV) and tomato yellow leaf curl virus (TYLCV) are the most damaging. 

Where do tomato leaf curl viruses occur in Australia?

Two viruses from this group occur in Australia. An Australian strain of tomato leaf curl virus (TLCV) is restricted to the northern parts of Queensland and the Northern Territory. The southern-most detection in Queensland has been in Mossman.  

An exotic strain of tomato yellow leaf curl virus (TYLCV) was detected in areas south of Brisbane and around Bundaberg early in 2006.

Symptoms and damage

TLCV (Figure 1), can be confused with several other tomato disorders such as tomato big bud, tomato yellow top, physiological leaf roll and phosphate and magnesium deficiency.

Figure 1. Three virus affected tomato plants in a field of healthy plants. (Photo courtesy of Barry Conde, Northern Territory Department of Business, Industry and Resource Development)

Table 1 compares the symptoms of TLCV with other diseases and disorders of tomatoes that may be confused with it.

Table 1.  Comparison of symptoms of TLCV on tomatoes and disorders with similar appearance

Disease	Symptom
Tomato leaf curl virus (TLCV)	Plants are stunted or dwarfed. Leaflets are rolled upwards and inwards. Leaves are often bent downwards and are stiff, thicker than normal, have a leathery texture and often have a purple tinge to the veins on the under side. Young leaves are slightly chlorotic (yellowish). Flowers appear normal. Fruit, if produced at all, are small, dry and unsaleable. Affected plants tend to be distributed randomly or in patches.
Tomato big bud	Produces enlarged green flowers. Affected plants tend to be distributed randomly or in patches.
Tomato yellow top virus	Leaflets are reduced in size and become rounded with yellowish, down-curled or up-curled margins. Affected plants tend to be distributed randomly or in patches.
Physiological leaf roll	Due to water stress, does not stunt plants. Young expanding leaf tissue is soft rather than rigid.
Phosphate deficiency	Stiff, stunted plants with a purplish tinge. All parts of the plant are reduced in size. More or less evenly distributed throughout a planting.
Magnesium deficiency	Yellowing of the interveinal areas of the middle and lower leaves. More or less evenly distributed throughout a planting.

Stages of disease development in tomato

The photos, Figures 2 to 5, appear by courtesy of Paul De Barro, CSIRO Entomology and show different stages of TLCV.

Spread of TLCV

Tomato leaf curl viruses are not transmitted in seed, soil or from plant to plant by handling. They stay in infected plants, some of which may be weed plants that do not show symptoms. The viruses are transmitted between plants by silverleaf white fly, Bemisia tabaci biotype B, which is a horticultural pest in coastal and some inland districts of Queensland and New South Wales. SLW is an established pest in Western Australia and cotton production systems in Queensland. (Refer to DPI&F Note on silverleaf whitefly).

Host plants of TLCV

Tomato (Lycopersicon esculentum) is the host plant on which tomato leaf curl viruses are commonly expressed in the field. However, the range of host plants that can be infected differs between the viruses, and not all hosts show symptoms of infection. Table 2 shows host plants that have been experimentally infected with TLCV under glasshouse conditions.

Table 2.  Common hosts of tomato leaf curl virus (TLCV)

Scientific name	Common name	Scientific name	Common name
Cyphomandra betacea	tamarillo	Phaseolus vulgaris	French bean
Datura stramonium	common thornapple	Physalis virginiana	perennial ground cherry
Lycopersicon esculentum	tomato	Solanum melongena	eggplant
Nicandra physalodes	wild hops	Solanum pseudocapsicum	Jerusalem cherry
Nicotiana benthamiana	native wild tobacco	Solanum seaforthianum	Italian jasmine
Nicotiana tabacum	tobacco	Solanum tuberosum	potato
Petunia x hybrida	petunia	Zinnia elegans	zinnia

NB: This host list does not include all host plants

Managing TLCV

In affected areas, control of tomato virus epidemics will depend on control of whitefly infestations. On-farm practices are particularly important where older crops are infected with tomato virus and also have high whitefly populations. Unless whiteflies on older infected crops are controlled, they may move to younger plantings and infect them with TLCV. More information is available on whitefly management in the publication 'Best management strategies for silverleaf whitefly in vegetable crops' by Siva Subramaniam, Paul De Barro and Alison Shields, or visit the silverleaf whitefly project home page.

There are two key points to managing the spread of TYLCV:

1. do not move infected or host plants or seedlings, nor infected SLW
2. control SLW on the farm, surrounding vegetation and seedling nurseries.

The best chance of achieving this is through good farm management and farm hygiene practices:

• use seedling plants produced in an area free from virus and whiteflies
• destroy old crops as soon as possible after final harvest
• control SLW adults before destroying crops to reduce the migration of SLW to other crops
• plant new crops as far away as practicable from existing crops which may harbour the virus and its carrier, silverleaf whitefly
• control silverleaf whiteflies using appropriate chemicals, application methods and IPM strategies
• maintain a high standard of weed control within and around crops to reduce hosts of both the virus and silverleaf whitefly.

More information on managing SLW in vegetable crops is available at: http://www2.dpi.qld.gov.au/horticulture/18512.html.

The links below are guides to chemical control options for SLW and should be used in conjunction with the good farm management practices listed above.

• A guide to choosing insecticides for silverleaf whitefly control in vegetables ( 49 KB)
• Insecticide permits for silverleaf whitefly control in Queensland - 2006 ( 33 KB)

Further information

If you have seen any of these plants infected with virus-like symptoms, contact the DPI&F Business Information Centre on 13 25 23 (free call in Queensland) for advice on what to do next. Alternatively contact your nearest DPI&F office or email the DPI&F Business Information Centre: callweb@dpi.qld.gov.au.

Further information on TLCV can be obtained from:

Denis Persley, Senior Plant Pathologist, DPI&F, Indooroopilly - 07) 3896 9375

John Thomas, Principal Plant Pathologist, DPI&F Indooroopilly - (07) 3896 9371

DPI&F information and services

• To access DPI&F's information and services, Queensland residents can contact the DPI&F Business Information Centre on 13 25 23 for the cost of a local call, from 8 am to 6 pm Monday to Friday (excluding public holidays). E-mail callweb@dpi.qld.gov.au. Non-Queensland residents phone (07) 3404 6999.

• Current national information on agricultural chemicals registered for use on all crops is available on the Infopest CD-ROM. Write to DPI&F, GPO Box 46, Brisbane, Qld 4001, E-mail infopest@dpi.qld.gov.au, visit the Infopest web page, or phone (07) 3239 3967 for further information.

Industry links

• Industry links is a page of links to various sites of interest to horticultural growers.

Acknowledgement

This publication compiled with the assistance of CSIRO.

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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.

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Last reviewed 19 September 2007