# New results on the combination of Sterile Insect Technique and enthomopathogenic fungi

Yves Dumont

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Yves Dumont. New results on the combination of Sterile Insect Technique and enthomopathogenic fungi. BIOMATH2025 - International Conference on Mathematical Methods and Models in Bio-sciences, Jun 2025, Sofia, Bulgaria. hal-05114796

HAL Id: hal-05114796

https://hal.inrae.fr/hal-05114796v1

Submitted on 16 Jun 2025

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Mathematical Methods and Models in Biosciences

June 15–20, 2025, Sofia, Bulgaria

https://biomath.math.bas.bg/biomath/index.php/bmcs

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Biomath Forum

# New results on the combination of Sterile Insect Technique and enthomopathogenic fungi

Yves Dumont

CIRAD, UMR AMAP, Pôle de Protection des Plantes, Saint Pierre, France
AMAP, Univ Montpellier, CIRAD, CNRS, INRA, IRD, Montpellier, France
Department of Mathematics and Applied Mathematics,
University of Pretoria, South Africa

yves.dumont@cirad.fr

Since 2017, *Bactrocera dorsalis*, the oriental fruit fly, has invaded Réunion island, causing significant damage to many crops, particularly mango orchards. It is necessary to combat this pest, using biological control methods [1].

The Sterile Insect Technique (SIT) is an old autocidal method used against pest and vectors of diseases. It is based on the releases of sterile males supposed to mate with wild females, such that the sterile-mated females will have no offspring, leading to a progressive decay of the wild population. Many SIT models have been developed taking into account that only one mating occurs. In fact, for many fruit flies species, like *Bactrocera dorsalis*, this is not the case: re-mating can occur after a certain time after the first mating. In addition, sterile males are not necessarily 100% sterile: residual fertility can occur such that sterile-mated females may deposit a certain proportion of viable eggs, $\varepsilon$.

In [2], we have developed a complex model to take into account these issues. In particular, we show that SIT is efficient, i.e. elimination is possible, only if $R_S \varepsilon < 1$, where $R_S$ is the basic offspring number related to the single and double-mated sterile females. We improve the result obtained in [3].

Then, we consider SIT in combination with an enthomopathogen soil's fungi that is used to control the fruit fly at the pupae stage. We show that this combination relax the constraint on the residual fertility and also decay the critical release rate. This works is part of the AttracTIS project, funded by Ecophyto 2021-2022.

**Keywords:** sterile insect technique, enthomopathogenic fungi, dynamical systems, monotone systems, residual fertility, re-mating, oriental fruit fly
References

[1] L. Moquet, V. Jacob, Y. Dumont, P. F. Duyck, H. Delatte, TIS et attractif contre *Bac- trocera dorsalis* à la Réunion, *Phytoma*, hal-04721445, 773:30-33, 2024.

[2] Y. Dumont, On the improvement of the Sterile Insect Technique by Entomopathogenic Fungi: impact of residual fertility and re-mating behaviour, hal-05003793, 2025.

[3] Y. Dumont, C. F. Oliva, On the impact of re-mating and residual fertility on the Sterile Insect Technique efficacy: Case study with the medfly, *Ceratitis capitata*, *PLOS Computational Biology*, 20:e1012052, 2024.