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Institut National de la Recherche Agronomique (INRA)

Research units

Banana, Plantain and Pineapple Cropping Systems

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Philippe Tixier
Le Lamentin, Martinique
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Tracking banana weevils

05/08/2011 - Article

Weevils cause considerable damage to affected banana plants. To understand how the pest spreads through fields, CIRAD launched a study of weevil movements, by fitting them with radio frequency identification tags. Using a model that simulates plot colonization, it was demonstrated that movements were affected by the structure of the environment. These results should make it possible to manage pest control by trapping more effectively.

The banana weevil (Cosmopilites sordidus ), an insect originating from southern Asia, now affects every production zone, and is the major pest in many regions, particularly West Africa. It is its larvae that damage banana plants, by boring galleries in the bulb, which prevent the plant taking up sufficient nutrients and sometimes cause it to fall. How do weevils move through the heterogeneous environments of banana plantations, and how do they choose their habitats? Lastly, what plot layouts would limit colonization of weevil-free plantings? It was these questions that a CIRAD team set out to address, using radiotelemetry and modelling.

Fitting weevils with RFID tags

Adult weevils spread slowly, by walking. Banana plots are colonized from already infested neighbouring plots or from reservoirs, such as semi-natural wild banana stands. Plot organization within an agricultural landscape thus plays an important role in the spread of weevils, as does the position of the various elements within plots - banana plants, harvest residues, cover crops, pheromone traps, etc.
Weevils were fitted with radio frequency identification (RFID) tags. The signals from the tags were detected to monitor weevil movements, with an accuracy of 30 centimetres. By analysing maps of their movements, it was possible to understand how individuals chose their habitats. These data were inputted into an individual-centred model (Cosmos ), which simulated weevil spatial spread and attacks as a function of the different elements in the cropping system. By comparing observed infestation data with simulated data, the model was validated and used to look into the effect on weevil behaviour of different banana plant spatial layouts.

How can banana plantings be organized to limit attacks?

The model showed that plots were colonized faster when banana plants were planted at regular intervals, rather than in clusters. It also revealed the essential role of the transitional zone between the banana planting and fallow areas for optimum trapping, a control method used in plantings producing bananas for export. These results mean that it is already possible to install interception traps containing an aggregation pheromone more effectively. To ensure all-round protection against weevils, work is due to continue, centring on population regulation by their natural enemies.

Literature

Vinatier F. et al., 2011. Factors and mechanisms explaining spatial heterogeneity: A review of methods for insect populations. Methods in Ecology and Evolution, 2: 11-22.