Panama disease overview

  • External symptom of Panama disease tropical race 4: Yellowing of lower and older leaves  Photo credit: Suzy Perry
    External symptom of Panama disease tropical race 4: Yellowing of lower and older leaves Photo credit: Suzy Perry
  • Internal symptom of Panama disease tropical race 4: Reddish-brown discolouration of the pseudostem
    Internal symptom of Panama disease tropical race 4: Reddish-brown discolouration of the pseudostem

If you believe you have plants infected with Panama disease tropical race 4, call Biosecurity Queensland immediately on 13 25 23.

General information

Overview

Cause

Panama disease is caused by the fungus Fusarium oxysporum f.sp. cubense. There are several races of Panama disease:

  • Race 1 infects Lady Finger, Sugar and Ducasse bananas, but not Cavendish.
  • Race 2 infects cooking bananas like Bluggoe and Blue Java bananas.
  • Race 3 infects only Heliconia species, not bananas.
  • Race 4 infects most varieties of bananas, including the main commercial variety, Cavendish

There are two important strains of this race:

Tropical race 4 is a serious threat to the Australian Cavendish banana industry. It is called 'tropical' race 4 because this strain of the fungus is capable of infecting Cavendish banana varieties growing in tropical conditions. Tropical race 4 has spread rapidly in South East Asia and was first detected in Australia near Darwin in 1997 and subsequently detected in Queensland in Tully in 2015.

Subtropical race 4 occurs in subtropical regions and usually only produces symptoms in Cavendish after a period of cold stress. Subtropical race 4 has been under quarantine control in south east Queensland, northern New South Wales and Western Australia for some time.

Disease symptoms

External symptoms

External symptoms of the disease include leaf yellowing, wilting of leaves and stem splitting. Symptoms are more obvious at particular times of year and crop stage. Environmental stress such as when conditions are too wet or too dry, too hot or too cold, increases the development of symptoms.

The energy required to produce a bunch can also increase symptom development. For example, plants may look healthy until bunches emerge, and then suddenly show leaf yellowing symptoms.

When the fungus blocks the water conducting tissue within the stem, it essentially starves the plant of water hence the initial symptoms are usually the yellowing of lower or older leaves. The leaves of infected plants lack a healthy green colour, and the edges or sections of the leaves will start to appear pale or yellow. This yellowing progression will continue towards the centre of the leaf. The leaf edges then turn brown before dying. As the lower leaves die they wilt and collapse, forming what can be described as a skirt around the plant.

The younger leaves may remain green and upright.

Stem splitting will usually occur at the base of the plant and is typically two or three layers thick. However, in the later stages of the disease, the splitting can extend much further up and deeper into the stem.

Remember to keep an eye out for any suspect plants that have yellow or wilting leaves and/or stem splitting.

Internal symptoms

While an infected plant may show internal symptoms it is very important that plants are not cut or removed. Cutting or removing an infected plant triggers the fungus to produce spores and increases the risk of spreading the disease around your property. Cutting or removing the plant also reduces the chances of getting a suitable sample for scientific testing.

Internal symptoms of the disease include discolouration of the vascular tissue in the corm and stem. This discolouration can range in colour from yellow to red through to dark brown or black, depending on how long the plant has been infected. If you have cut down a plant and see these symptoms, it is important to contact Biosecurity Queensland so that a sample can be taken as quickly as possible and sent to a laboratory for diagnostic testing.

Spread

The disease is easily spread by the movement of infected planting material. Regulations on plant movement are in place to prevent this.

The disease can spread over short distances via root to root contact and through soil. Spread can also occur from parent plants to suckers. The disease can also be moved with soil, water and on contaminated equipment. Fungal spores can survive in the soil for as long as 30 to 40 years.

Control

Prevention is the most effective disease control measure. To help prevent Panama disease tropical race 4 from infecting your property, implement on-farm biosecurity practices such as wash-down and decontamination procedures and always use clean, disease free planting material such as tissue culture plants or plants from a proven disease free source.

Managing access to properties and training staff in hygiene management and early disease detection is vital to ensuring early identification and preventing disease introduction. 

Parts of Queensland are free of some strains of Panama disease. The banana industry and the Queensland Government are keen to minimise the effects of this disease by eradicating infections where possible and restricting movement of bananas from infected areas.

The key strategies for managing Panama disease tropical race 4 in Queensland include:

  • controlling the movement of infested planting material, soil or contaminated equipment
  • establishing criteria for ensuring planting material and nursery plants are free of disease
  • seeking disease-resistant varieties in collaboration with world breeding programs and collections.
Reporting suspect plants

In most circumstances, it will be field staff who will first notice symptomatic plants.

Therefore it is essential to ensure all staff are able to identify potentially diseased plants and understand the importance of reporting any suspect symptoms to farm management immediately.

Suspect plants should be marked with flagging tape or spray paint.

Also, the end of the row the plant is in should be marked and row number, location of the plant within the row, and specific block noted. If possible, take photos of the symptoms.

In Queensland, under the Biosecurity Act 2014, Panama disease tropical race 4 is category 1 restricted matter. This means that, by law, plants showing signs of disease must be reported to Biosecurity Queensland on 13 25 23 as soon as practicable and not more than 24 hours after becoming aware of the symptoms.

Further information

Last updated 28 July 2017