While no one could deny the fact that Europeans love eating bananas, it is easy to overlook the fact that Europe is actually responsible for growing them too.
Thus bananas have been a focus of one of ENDURE’s case studies, with a team that brings together representatives from ENDURE members CIRAD (France), the International Biocontrol Manufacturers Association and Wageningen University (Netherlands), working with partners from CARBAP (African Centre for Banana and Plantain Research, Cameroon) and ICIA (Instituto Canario de Investigaciones Agrarias, Canary Islands, Spain, .
The team is led by Jean-Michel Riséde and François Côte from CIRAD, the first based on the French island of Guadeloupe and the latter in Montpellier, France. At a recent meeting of the banana case study, we caught up with Jean-Michel to find out more about their work on a fruit whose popularity continues to grow.
QUESTION: Why are bananas an important crop for consideration in a European network such as ENDURE?
JEAN-MICHEL RISEDE (pictured left): There are several reasons for a banana case study in ENDURE. Partly it is because bananas are one of the world’s principal fruit crops, in terms of both the tonnage produced and traded. As a consequence, it is the fruit that we most often consume, and that is true in Europe too. To take just one statistic, in 2006 the average consumption per inhabitant of the European Community was in the range of 10.5kg of bananas. The second point, and this surprises a lot of people, is that banana production exists in Europe. Here we are talking about the outermost regions of Europe, principally the Canary Islands (Spain) and the Antilles (Guadeloupe and Martinique, France). There are also some bananas produced in Madeira (Portugal) and, to a lesser extent, in Greece and in Cyprus.
It is important to realise that for many decades the bananas we eat in Europe have been produced in intensive systems that have used elevated levels of pesticides. This has begun to change in the past 10 years and it was important in a Network of Excellence like ENDURE to bring together this new knowledge on alternative and innovative ways of producing bananas using much lower quantities of pesticides. We want to be able to offer and build with European producers alternative strategies and innovations and to suggest ways bananas can be produced differently elsewhere in the world too. The multi-partner approach within ENDURE means we can exchange with other researchers working on bananas in Europe and that gives us the ability to change the scale of what can be achieved; we can look at the alternatives that exist and see how this needs to be completed in terms of the scientific research that is still needed and so accelerate the process of using less pesticides for banana production.
QUESTION: What are the most important pest and disease problems facing banana growers and how are they usually tackled?
JEAN-MICHEL RISEDE : In the climatic zones where bananas are produced they are attacked by multiple pests and diseases. There are pests and diseases capable of attacking the roots of the banana, the rhizome (the bulb), the pseudo-stem, the leaves and the fruits. And they cannot only be attacked in the field, but damage can also be caused that does not become obvious until the post-harvest stage, when the bananas are being stored and transported. We have to understand the biology of the pests and diseases so we can ascertain at what stage in the cycle action needs to be taken and to grow the plants in ways that might avoid these problems.
One important problem are the fungal diseases we find in lots of banana production zones, principally Black Leaf Streak Disease (BLSD), which is the more aggressive, and yellow Sigatoka. The diseases attack the photosynthetic surface of the leaves and, although bananas still form, they cause premature ripening of the fruit. This is a problem as it may take 10 or 12 days to export the fruit to Europe and by the time it arrives it is fit only for the dustbin, which is catastrophic for the producer.
Another problem are nematodes, microscopic worms less than 1mm in length. In the head of the pathogenic nematodes there is a mouth region where you find a kind of needle which they stick into the cells of the roots. They have a very short reproductive cycle - about three weeks - which makes for exponential multiplication and you can have 100,000 nematodes for 100 grams of root. The nematodes cause cell necrosis (death) and where this results in lots of lesions in the root system, what does the banana tree do? It quite simply falls over, causing a direct loss for the producer.
Thirdly there are black weevils, the larvae of which develop in the rhizome or bulb of the tree where they dig out small holes. This also causes necrosis and the tree is finished. There are other bacterial and fungal problems too, but these are three major problems you find in almost all large production areas.
To combat these, for many years the answer was, above all else, to use chemicals. Chemicals are relatively easy to use but there is the potential for pollution to plants, the soil and water, and in some cases this pollution was not only potential but actually happened. There is another problem, too, in combating BLSD and yellow Sigatoka with chemical treatments as fungicide resistance develops. This means that although you continue to use the same fungicide, it doesn’t have the same efficacy and the fungus continues to develop.
These problems mean there was a real necessity to change production methods that relied on chemical controls and that challenge has been met in recent years. ENDURE’s banana case study has meant we can stop and take stock of what elements are available for protecting banana crops against these pests and diseases in a different way.
For example, to combat soil-borne problems such as nematodes we know it is important to combine what we call 'soil sanitation' and 'plant sanitation'. This means introducing crop rotation: removing the banana trees from the plot for 12 to 18 months means the banana-hosted nematodes disappear too as they cannot survive without their host, and we can then replant with in-vitro plantlets, which are produced in a laboratory and thus free from infestation.
For fungal diseases a different strategy is needed, although for the moment we have to still use pesticides. Reducing the use can be achieved through using ‘witness’ plots to monitor the evolution of the disease and establish at which moment treatment is necessary rather than spraying systematically, which involve treatments every week. In many parts of the world treatments have been systematic, regardless of the evolution of the disease, and this results in problems with resistance. In this situation all you can do is change the fungicide and apply it all the time as a preventative measure.
Above all else, for a truly sustainable approach we have to have more genetic diversity in the plants. It is surprising to a lot of people, but all the bananas traded across the globe are of one variety, Cavendish, and while it is a productive banana, it is susceptible to lots of parasites. If we could balance that quality of fruit with resistance to BLSD, for example - and we know there are banana varieties resistant to it - it would be a major step and we could do this through conventional breeding.
For combating black weevil the technique most in fashion is to use a synthetic pheromone which attracts the insects, which are then captured in a plastic trap. There is some education to do on this technique; for example, certain periods are much more effective than others and mass trapping can be conducted during these times. There are other methods too, such as changing the spatial organisation of the plot and using companion plants to slow the distribution of weevils. The idea is to arrive at a cropping system which is truly integrated.
QUESTION: What has the case study been focusing on?
JEAN-MICHEL RISEDE : There are three components. One has been to identify the quantity of pesticides used in each production area, including Africa and Latin America, from which we know European producers use fewer different types of pesticides. Secondly, through pooling our experience, we have assessed possible alternatives that can be used in the short term and possible innovations for the mid term. The leaflets we are about to release will explain all this, providing some global information as well as dealing with some specific problems that I outlined earlier. Thirdly, we have identified some gaps in our knowledge, those areas that offer potential for future research projects.
QUESTION: How will you share this knowledge with growers and advisors?
JEAN-MICHEL RISEDE : The leaflets will be part of this. It is important to note that the leaflets were not written by researchers working alone, but in collaboration with producers. We have been looking for those areas where we can make the connection between research, producers and extension services. Two concrete examples are that of Guadeloupe and Martinique, where we have already developed with producers a 'Plan Banana Durable' for testing cropping system prototypes that are being trialled in producers' fields, and in the Canary Islands, ICIA is seeking to conduct a similar project on sustainable production of bananas in partnership with producers.
QUESTION: What benefits has this team working brought to the case study?
JEAN-MICHEL RISEDE : It has allowed us to bring together our different knowledge on reducing the use of pesticides. In the short term, the leaflets allow us to contact directly the end users and extension officers, and in the mid term, we can identify what research is needed.