Plantain plant-parasitic nematodes

  • PhD: Israël Tankam Chedjou, University of Yaoundé I, Dec. 2015-April 2021
  • Supervisors: J. J. Tewa, S. Touzeau, F. Grognard, L. Mailleret
  • Partners: CIRAD, Centre africain de recherches sur bananiers et plantains (CARBAP)

Context

  • Plantain: major staple food – Cameroon: 2% GDP
  • Nematodes (Radopholus similis) create root lesions and induce great damages (banana toppling)
  • Control methods: nematicides vs cropping practices (soil sanitation), tolerant or resistant banana varieties, biological control
  • Existing model(s): complex interaction model for the West Indies [Tixier et al. 2006]

P. Tixier, J.-M. Risède, M. Dorel, E. Malézieux. Modelling population dynamics of banana plant-parasitic nematodes: A contribution to the design of sustainable cropping systems. Ecological Modelling 198(3): 321–331, 2006. DOI: j.ecolmodel.2006.05.003

Objectives

  • To develop a model describing plantain plant-parasitic nematode damages in a plantation
  • To design efficient and sustainable control strategies to limit damages, including alternative methods to nematicides

Work progress

Achieved

  • Seasonal interaction model between the nematode Radopholus similis and plantain roots
    • Doubly hybrid system: roots only grow until flowering; the plant is replaced either by a lateral shoot, or by a new sucker at the end of each cropping season
    • Model analysis assuming that root infestation dynamics is fast
      • local stability results for the pest-free equilibrium (basic reproduction number)
      • exact solutions for the linearised model
    • Conditions on the pesticide load or the delay between cropping seasons to ensure nematode extinction

    I. Tankam Chedjou, S. Touzeau, F. Grognard, L. Mailleret, J.-J. Tewa. A multi-seasonal model of the dynamics of banana plant-parasitic nematodes. Paper and oral presentation in: CARI’2018 – 14th African Conference on Research in Computer Science and Applied Mathematics, Stellenbosch, South Africa, 14-16 October 2018. HAL Id: hal-01871510v1

    I. Tankam Chedjou, S. Touzeau, L. Mailleret, J.-J. Tewa, F. Grognard. Modelling and control of a banana soilborne pest in a multi-seasonal framework. Mathematical Biosciences 322: 108324, 2020. DOI: 10.1016/j.mbs.2020.108324. HAL Id: hal-02775460

  • Optimisation problem

    First approach: the banana plant is pulled out at the end of the cropping season and a pest-free sucker is bought and planted at the beginning of the next season, allowing for a fallow period between cropping seasons

    • Agricultural control: fallow periods, which reduce the nematode population in the soil (no host to feed and reproduce); 2 cases:
      1. constant fallow period
      2. variable fallow period
    • Aim: to maximise the cumulated yield (affected by the nematode population), while minimising the costs of nursery-bought pest-free suckers, on a fixed time horizon that lasts several cropping seasons
    • Results:
      1. constant fallow: existence of an optimal solution, location computed for small infestations
      2. variable fallow: existence of an optimal strategy and numerical illustrations

    I. Tankam Chedjou, S. Touzeau, F. Grognard, L. Mailleret, J.-J. Tewa. An agricultural control of Radopholus similis in banana plantations. Contributed talk in: ECMTB 2018 – 11th European Conference on Mathematical and Theoretical Biology, Lisbon, Portugal, 23-27 July 2018. HAL Id: hal-01859995

    F. Grognard, I. Tankam Chedjou, Y. Fotso Fotso, S. Touzeau, 2019. Modelling, control, and optimization for tropical agriculture. Oral presentation in: CMPD5 – Computational and Mathematical Population Dynamics, Fort Lauderdale, USA, 19-24 May 2019. HAL Id: hal-02139546

    I. Tankam Chedjou, S. Touzeau, F. Grognard, L. Mailleret, J.-J. Tewa, 2019. Agricultural control of Radopholus similis in banana and plantain plantations. Oral presentation in: BIOMATH 2019 – International Conference on Mathematical Methods and Models in Biosciences, Bȩdlewo, Poland, 16-22 June 2019. HAL Id: hal-02139560

    I. Tankam Chedjou, F. Grognard, J.-J. Tewa, S. Touzeau. Optimal and sustainable management of a soilborne banana pest. Applied Mathematics and Computation 397: 125883, 2021. DOI: 110.1016/j.amc.2020.125883 – arXiv 2020: 2007.12606 – HAL Id: hal-03111065

    More realistic approach: generally, a lateral shoot that develops from the rhizome of the mother plant is kept for the next cropping season, which does not allow for a fallow period; occasionally, the plant is pulled out and replaced by a nursery-bought pest-free sucker

    • Controls: combining chemical control (nematicides), which induces an adverse effect on the plant growth, cropping practices, trap plants
    • Aim: to maximise the cumulated yield, while minimising the control costs and the costs of nursery-bought pest-free suckers, on a fixed time horizon that lasts several cropping seasons
    • Results:

    I. Tankam Chedjou, F. Grognard, J.-J. Tewa, S. Touzeau. When and how to fallow: first steps towards banana crop yield improvement through optimal and sustainable control of a soilborne pest. Journal of Interdisciplinary Methodologies and Issues in Science, Digital Agriculture in Africa, 2021. DOI: 10.18713/JIMIS-120221-8-4 – HAL Id: hal-03103785

  • PhD defence 9 April 2021 (postponed due to pandemic)

    Israël Tankam Chedjou. Modelling, analysis and control of plantain plant-parasitic nematodes. University of Yaoundé I, Cameroon, 2021. HAL Id: tel-03217816

Misc

  • Recipient of an EMS-Simons for Africa PhD development grant, November 2018 deadline
  • Recipient of the 2021 Ovide Arino Outreach Award (OAOA), a joint ESMTB and SFBT prize
  • Postdoc in 2022 at the WAVE Center in Abidjan, Ivory Coast, funded by the Bill & Melinda Gates Foundation, in collaboration with the Epidemiology and Modelling Group headed by Chris Gilligan at the University of Cambridge, UK

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