Banana bunchy top

Banana bunchy top is caused by banana bunchy top virus (BBTV), a plant virus transmitted by a small black insect called the banana aphid (Pentalonia nigronervosa).

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

Key symptoms

• Dark green on lighter green, dot-dash flecks (sometimes called Morse code streaking/patterning) on leaves.
• Dot-dash flecks are initially visible along the lower edge of the leaf's midrib, then progress to the leaf veins adjacent to the midrib, and gradually becoming more prominent across the leaf blade.
• Eventually 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 develop a choked or 'bunched" appearance.
• Affected leaves often appear more upright with pale yellow margins, and 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. 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.

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.

If you are unsure if your banana plants have banana bunchy top disease symptoms, report it so a trained inspector can diagnose it for you.

• Banana bunchy top is known to occur in Africa, Asia, Australia and South Pacific islands.
• In Australia, banana bunchy top is present in South East Queensland and northern NSW.
• North Queensland, Western Australia and Northern Territory commercial banana production areas remain free of the disease.

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

• Banana aphids can spread banana bunchy top by feeding on infected banana plants. The aphids then transmit the virus by feeding on healthy banana plants.
• Once infected, the virus spreads throughout the whole plant.
• Infected banana plants do not show bunchy top symptoms until 2 or more new leaves have been produced after being infected by the banana aphids. This takes between about 19 days in summer to about 125 days in winter.
• Once bunchy top symptoms are visible, the newly infected plant becomes a source of the virus for further spread.
• Banana aphids can acquire the virus after at least 4 (but usually about 18) hours of feeding on an infected plant.
• Aphids can retain the virus through their adult life, a period of 15–20 days.
• Banana aphids can then transfer the virus to susceptible healthy plants as they feed.

Banana bunchy top is a serious viral 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. Banana bunchy top infected backyard plants can act as a source of infection that can affect neighbouring plantations if not reported promptly.

The movement of asymptomatic, but infected banana planting material (e.g. corms, bits, suckers, potted plants) or plant material carrying virus-infected banana aphids is responsible for moving this disease long distances.

In Australia and most other countries banana bunchy top only occurs on banana. Localised disease spread occurs from plant to plant by the insect vector, the banana aphid (Pentalonia nigronervosa). Other aphid species do not transmit BBTV.

The virus is not spread by mechanical means.

If you have stunted or unthrifty banana plants, examine the banana leaves for short dark green on lighter green dot-dash lines starting from the mid-rib. 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 mid-rib.

Plants with advanced infection 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, report it.

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

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

The Farm Biosecurity Manual for the Banana Industry (PDF, 1.4MB) provides practical advice for banana growers on managing biosecurity risks

Protect your farm from plant pests and diseases:

• Protect your farm from emergency plant pests
• Understand good farm biosecurity
• Visit the farm biosecurity website

Bunchy top cannot be cured and infected plants must be destroyed.

The National Banana Bunchy Top Virus Project currently operates cross-border in South East Queensland and northern NSW. Contact the Banana Bunchy Top Hotline on 1800 068 371 for assistance if you have found bunchy top infected plants.

It is illegal to move a banana plant out of the southern banana biosecurity zone (PDF, 420KB) without authorisation. Penalties apply for breaches of the law.

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

Under Queensland legislation if you suspect the presence of banana bunchy top, you must report it.

If you have seen banana bunchy top within the southern banana biosecurity zone (PDF, 420KB), contact the Banana Bunchy Top Hotline on 1800 068 371.

If you have seen banana bunchy top outside of the southern banana biosecurity zone, you must report it to Biosecurity Queensland on 13 25 23 or contact the Exotic Plant Pest Hotline on 1800 084 881.

If you think you have found the disease, you must take all reasonable and practical steps under your control to minimise any associated risks. This is called a general biosecurity obligation (GBO).

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

If you want to move banana plants (other than fruit), soil on which a banana plant has been growing, or machinery used in production of the plants into Queensland or out of any of the 4 biosecurity zones for bananas, you will need to apply for a biosecurity certificate.

Your compliance with these legal requirements will prevent the spread of banana bunchy top and other serious pests and diseases that could threaten our valuable agricultural industries.