Banana bunchy top virus

Previous Next

Scientific name

Babuvirus musae

Cause

Banana bunchy top disease is caused by banana bunchy top virus, a plant virus transmitted by a small black insect called the banana aphid (Pentalonia nigronervosa) and the closely related aphid species P. caladii.

Banana bunchy top virus does not affect human or animal health.

Other names

• Banana bunchy top disease
• Banana bunchy top
• Bunchy top of banana
• Cabbage top of banana
• Curly top of banana

Description

Key symptoms

• On the leaves, there are dark-green dot-dash flecks (sometimes called 'Morse code' streaking/patterning).
• The dot-dash flecks are initially visible along the leaf's midrib, then progress to the leaf veins adjacent to the midrib, gradually becoming more prominent across the leaf blade. Eventually the dot-dash flecks can form into irregular streaking.
• Leaf flecks and streaking are most visible when viewed from the underside of leaves.
• Flecks in veins can form a characteristic 'hook' shape at the point where the midrib meets the leaf blade.
• Vein-flecking can also be seen on the petioles and in the leaf sheaths of stems.
• Growth of the whole plant is reduced and emerging leaves become shorter and narrower, developing a choked or 'bunched' appearance.
• Affected leaves often appear more upright than others and have pale-yellow margins. They may have wavier leaf edges than normal.
• Severely affected plants can develop a skirt of dead leaves as affected leaves die off but remain attached to the stem. These symptoms are commonly seen in unmanaged plants or backyard plants.

Plant stage and plant parts affected

The whole plant is affected by banana bunchy top virus. If infected at an early stage, plants become very stunted and rarely produce bunches. If infected at a later stage, distorted bunches may be produced.

May be confused with

Environmental stresses can cause 'choke throat' of bananas, a disorder where the bunch is unable to emerge from the plant, or the bunch is misshapen and the plants look stunted. These plants will not have the dot-dash flecking, discontinuous leaf streaks and hook patterning on banana leaves that are distinctive symptoms of banana bunchy top virus.

If you suspect your banana plants have symptoms of banana bunchy top virus, report it. A trained inspector can then make a diagnosis.

Distribution

• Banana bunchy top virus is known to occur in Africa, Asia, Australia (south-eastern Queensland and northern New South Wales) and South Pacific islands.
• Commercial banana production areas in North Queensland, the Northern Territory and Western Australia remain free of the disease.

Hosts

• Banana plants, including commercial and homegrown varieties
• Native and ornamental bananas
• Manila hemp (Musa textilis)
• Ensete (Ensete ventricosum)

In Australia and most other countries, banana bunchy top disease only occurs on banana plants.

Life cycle

• The aphids Pentalonia nigronervosa and P. caladii can spread banana bunchy top virus by feeding on infected banana plants then feeding on healthy banana plants.
• Once a plant is infected, the virus spreads throughout the whole plant.
• Infected banana plants do not show symptoms immediately. Symptoms will not appear until after 2 or more new leaves have been produced. This takes about 19 days in summer and longer in cooler weather (about 125 days in winter).
• Once symptoms are visible, the newly infected plant becomes a source of the virus for further spread.
• Aphids can acquire the virus after about 4 hours of feeding on an infected plant. However, they usually acquire it after about 18 hours of feeding.
• Aphids can retain and transmit the virus through their adult life, a period of 13 to 20 days.
• Aphids can fly up to 100 metres, so they can spread the virus to susceptible healthy plants in this range.

Plants affected

• Banana

Impacts

Banana bunchy top virus is a serious disease of bananas. Affected plants rarely produce fruit, which results in significant production losses, and once plants have become infected there is no cure.

Backyard plantings of banana are common in Queensland and can be significantly affected by the disease. If not reported promptly, infected backyard plants can become a source of infection and the disease can spread to neighbouring plantations.

How it is spread

The disease can spread over long distances through the movement of asymptomatic but infected banana planting material (such as corms, bits, suckers and potted plants). It can also be spread over long and short distances through the movement of virus-carrying aphids (Pentalonia nigronervosa and P. caladii) on plant material.

Other aphid species do not transmit banana bunchy top virus, and it is not spread by mechanical means.

Monitoring and action

If you have stunted or unthrifty banana plants, check the banana leaves for short dark-green dot-dash lines surrounded by lighter green, starting from the midrib. You can see them best if you hold the leaf up to the light and look through from the underside of the leaf. There may also be dark-green stripes along the midrib.

Plants with advanced infection will have stunted-looking leaves and a bunched appearance (bunchy top). If bunches are present, they may be small and deformed.

If you suspect banana bunchy top virus, report it.

Do not cut or disturb infected plants or move contaminated plant material off your property—this can spread the disease. Plants should be treated by a trained inspector only.

Prevention

Use banana plants propagated from tissue culture under the Quality Banana Approved Nursery (QBAN) scheme—these are recommended as the safest disease-free source of planting material. QBAN plants are now widely available for both commercial and backyard use.

Use these resources to learn more about how to protect your farm from plant pests and diseases:

• Protecting your farm from plant pests and diseases
• My property biosecurity
• Farm biosecurity.

Control

Plants that are infected with banana bunchy top virus cannot be cured and must be destroyed.

The National Banana Bunchy Top Virus Program works with communities in south-eastern Queensland and northern New South Wales to prevent spread of the disease from these areas.

Legal requirements

Banana bunchy top virus is category 1 restricted matter under the Biosecurity Act 2014.

Under the Biosecurity Act, everyone in Queensland has a general biosecurity obligation to report biosecurity risks (such as banana bunchy top virus) and take action to prevent or minimise them.

Movement restrictions are in place in Queensland to prevent the introduction and spread of banana pests such as banana bunchy top virus.

You need to apply for a biosecurity certificate if you want to move any of the following items into Queensland or out of any of the 4 biosecurity zones for bananas:

• banana plants or material (other than fruit)
• soil on which a banana plant has been growing
• machinery used in production of banana plants.

Penalties apply if you do not comply with the restrictions.

Further information

• Read Plant Health Australia's fact sheet on bunchy top disease (PDF, 704KB).