Bunchy top is caused by a virus spread on infected planting material or by the banana aphid, Pentalonia nigronervosa, when it feeds on diseased plants and moves to healthy ones.

Bunchy top produces dark green, dot-dash flecks running along leaf veins and hooking down along the midrib, and dark green streaks running vertically down the leaf sheath into the pseudostem of the banana plant. New emerging leaves are progressively shorter, narrower and more erect. The stools fail to produce fruit.

It cannot be cured, and affected plants must be destroyed. Control depends on prompt detection and destruction of infected stools. There are strict quarantine restrictions to prevent movement of contaminated planting material. Control also depends on the use of uninfected planting material and intensive eradication schemes.

Bunchy top has not been eradicated from southern Queensland and the banana industry and the Queensland Government are keen to ensure the disease is kept out of north Queensland. Bunchy top is kept in check by constant vigilance of inspectors and strict industry controls.

Key strategies for bunchy top control are:

• gradual eradication from South East Queensland and northern New South Wales by maintaining pressure on infested areas
• use of tissue-cultured, uninfected planting material when possible
• development of sensitive detection tests
• contributions to international research on alternative hosts and strains of the virus
• development of contingency plans for dealing with infection if bunchy top occurs in north Queensland.

Affected plants do not produce fruit. This causes significant loss of production on commercial farms.