Multiple fungal organisms are known to cause Crown end rot (CER) in bananas. The following research is focused on the more serious form of CER commonly known as Chalara where the rot extends into the fruit (caused by Thielaviopsis musarum). Disease symptoms are typically observed in the supply chain during cooler periods of the year (winter). Chalara is sporadic in occurrence, making it difficult to conduct research trials with the disease. Department of Agriculture and Fisheries researchers have now developed an inoculation technique that mimics the development of Chalara in the supply chain, enabling researchers to screen and evaluate alternative management options.
Overall, the inoculation technique developed is rapid and reliable and the results are reproducible. Even though the technique was specific for Chalara (T. musarum), crown mould assessments were also obtained. Ideally a successful test product should have efficacy against T. musarum and the range of fungi that cause crown mould.
Research has shown that a range of farm management practices have some incremental influence on disease management of crown end rot (CER), from site selection to irrigation practices through to packaging and dispatch. Specifically, good field and shed hygiene practices help reduce fungal spores making it easier and more effective for post-harvest fungicides to do their work. However, to reduce reliance on fungicide use and address issues associated with chemical resistance, research into potential alternative post-harvest treatments are being investigated.
Twelve post-harvest treatments including disinfectants, biological/organic treatments and alternative fungicides have been screened using clusters of bananas and observing the natural development of CER symptoms.
Crowns of each of the clusters were dipped in various treatments (for 30 seconds or 3 minutes), then ripened under standard ripening conditions. Once the fruit was ripened, the symptom development of CER was rated on a scale of 0-7 (7 being the most severe).
The table below provides a summary of the performance rating of each of the post-harvest treatments tested.
If you would like more information on this trial contact the better bananas team at betterbananas@daf.qld.gov.au or 13 25 23.
Understanding what species are capable of hosting the fungal organism that causes Panama disease will help inform how weeds and ground covers are managed in areas infested with the disease.
Work in Far North Queensland has used Panama disease race 1 as a surrogate for tropical race 4. Field surveys conducted in the region have identified plant species common to banana plantations that may act as potential alternative hosts. In this context, a host is defined as a plant in which the fungus can survive, often without obvious disease symptoms apparent.
Weed and ground cover species were collected from farms in Far North Queensland with a history of race 1 infection. In total 115 samples from 20 different plant species were analysed for the presence of the fungal organism (Fusarium oxysporum f.sp cubense) that causes Panama disease race 1.
Roots from each of the plant samples were washed to dislodge excess soil before being surface sterilised. Segments of roots were placed in Fusarium selective media, and incubated for 3-5 days to allow fungal growth. The recovered populations were sent to a specialist diagnostic lab in Brisbane for formal identification.
Race 1 was found living within four different species commonly found co-habiting Far North Queensland banana farms. These species were, spiny spider flower (Cleome aculeata), Youngia japonica, crowsfoot grass (Eleusine indica) and summer grass (Digitaria ciliaris).
Panama disease race 1 (R1) was used as a surrogate for Panama disease tropical race 4 (TR4), as access to TR4 infested banana properties in Queensland is restricted.
Panama disease subtropical race 4 (SR4) was used as a surrogate for tropical race 4 (TR4), as SR4 is more closely related to TR4 than other races of the disease.
The above information is a guide only, as multiple organisms may be involved and simultaneously cause symptoms.
If you notice any crown end rot symptoms or want further information, contact the better bananas team at betterbananas@daf.qld.gov.au or 13 25 23.
These results show that it may be necessary to change your post-harvest treatment products, depending on the organism/s you are having issues with and the location of your farm.
The length of time bananas spend in the supply chain can have a significant impact on the development of crown end rot (CER).
Researchers conducted a simulation experiment, where Cavendish (Williams) and Lady Finger clusters were held 1, 2, 3 and 4 weeks prior to being ripened. The fruit for the experiments was sourced from a commercial property and all fruit was treated with a post-harvest chemical (prochloraz). To ensure a fair comparison, fruit from different positions in the bunch (top, middle and bottom hands) were assessed in case this was also a contributing factor. Once the fruit was ripened, the symptom development of CER was rated on a scale of 0-7 (7 being the most severe).
As seen in the graph below, the experiment with Cavendish fruit revealed fruit held longer within the supply chain resulted in relatively more severe symptoms of CER than fruit that would generally move through quicker. However, the overall symptom development was low as you can see in the graph below.
As seen in the figure below, the simulation experiment using Lady Fingers showed similar results to Cavendish fruit in that fruit held for longer prior to ripening produced more severe symptoms of CER. However the overall symptom development was low as you can see in the graph below.
If you would like more information on this trial contact the better bananas team at betterbananas@daf.qld.gov.au or 13 25 23.
Crown end rot (CER) of bananas is a serious cause of post-harvest quality loss for banana fruit. As the name suggests, the rot begins at the cut surface of the crown, and depending on the severity, can extend down the neck of the fruit and into the fingers. There are several fungi that can cause CER symptoms and the visual appearance of those symptoms may indicate what fungal organism is responsible. However, multiple fungi can simultaneously cause symptoms, so it can be difficult to distinguish the difference with the naked eye.
Click here for more information and photos of the symptoms typically associated with each fungal organisms.
Currently, the most effective management strategy for CER is the application of post-harvest fungicides. Products containing thiabendazole (e.g. Tecto®) and prochloraz (e.g. Protak®) are registered for post-harvest use in bananas.
Recent research has indicated that some of the organisms that cause CER are less sensitive to thiabendazole based products, particularly in the coastal regions of Far North Queensland. These organisms remain more sensitive to products containing prochloraz. Simulation studies have also shown that the longer banana fruit is held in the supply chain before ripening, the greater the risk of developing more severe symptoms of CER. Research has also investigated alternative post-harvest products.
See below for more information on this research.