An agent-based model to simulate the boosted Sterile Insect Technique for fruit fly management

Diouf, Esther Gnilane; Brévault, Thierry; Ndiaye, Saliou; Faye, Émile; Chailleux, Anaïs; Diatta, Paterne; Piou, Cyril

doi:10.1016/j.ecolmodel.2022.109951

Cited by 16 publications

(11 citation statements)

References 76 publications

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“…In-field control : Confirming if flies are investing more or less in reproduction versus longevity at different times of the year, especially if there are critical cues that cause switching between the two, would enhance the ability to create predictive population models for pest management. We are aware of only three predictive population models for polyphagous Bactrocera species that have been tested against independent data sets: one for B. tryoni [ 22 ] and two for B. dorsalis [ 124 , 126 ]. All three models consistently over-predicted the size of fly populations for large periods of the year.…”

Section: Why Is All This Important?mentioning

confidence: 99%

The Fallacy of Year-Round Breeding in Polyphagous Tropical Fruit Flies (Diptera: Tephritidae): Evidence for a Seasonal Reproductive Arrestment in Bactrocera Species

Clarke

Measham²

2022

Insects

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The genus Bactrocera (Diptera: Tephritidae) is endemic to the monsoonal rainforests of South-east Asia and the western Pacific where the larvae breed in ripe, fleshy fruits. While most Bactrocera remain rainforest restricted, species such as Bactrocera dorsalis, Bactrocera zonata and Bactrocera tryoni are internationally significant pests of horticulture, being both highly invasive and highly polyphagous. Almost universally in the literature it is assumed that Bactrocera breed continuously if temperature and hosts are not limiting. However, despite that, these flies show distinct seasonality. If discussed, seasonality is generally attributed to the fruiting of a particular breeding host (almost invariably mango or guava), but the question appears not to have been asked why flies do not breed at other times of the year despite other hosts being available. Focusing initially on B. tryoni, for which more literature is available, we demonstrate that the seasonality exhibited by that species is closely correlated with the seasons of its endemic rainforest environment as recognised by traditional Aboriginal owners. Evidence suggests the presence of a seasonal reproductive arrest which helps the fly survive the first two-thirds of the dry season, when ripe fruits are scarce, followed by a rapid increase in breeding at the end of the dry season as humidity and the availability of ripe fruit increases. This seasonal phenology continues to be expressed in human-modified landscapes and, while suppressed, it also partially expresses in long-term cultures. We subsequently demonstrate that B. dorsalis, across both its endemic and invasive ranges, shows a very similar seasonality although reversed in the northern hemisphere. While high variability in the timing of B. dorsalis population peaks is exhibited across sites, a four-month period when flies are rare in traps (Dec–Mar) is highly consistent, as is the fact that nearly all sites only have one, generally very sharp, population peak per year. While literature to support or deny a reproductive arrest in B. dorsalis is not available, available data is clear that continuous breeding does not occur in this species and that there are seasonal differences in reproductive investment. Throughout the paper we reinforce the point that our argument for a complex reproductive physiology in Bactrocera is based on inductive reasoning and requires specific, hypothesis-testing experiments to confirm or deny, but we do believe there is ample evidence to prioritise such research. If it is found that species in the genus undergo a true reproductive diapause then there are very significant implications for within-field management, market access, and biosecurity risk planning which are discussed. Arguably the most important of these is that insects in diapause have greater stress resistance and cold tolerance, which could explain how tropical Bactrocera species have managed to successfully invade cool temperate regions.

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Section: Why Is All This Important?mentioning

confidence: 99%

The Fallacy of Year-Round Breeding in Polyphagous Tropical Fruit Flies (Diptera: Tephritidae): Evidence for a Seasonal Reproductive Arrestment in Bactrocera Species

Clarke

Measham²

2022

Insects

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“…Laboratory studies have shown that these males can transfer this insect growth regulator to females for up to ten days through simple contact, even if mating fails, effectively preventing them from producing viable offspring (Laroche et al, 2020). Mathematical and agent-based modelling identified the conditions of where field efficacy may be greater than for classical SIT (Diouf et al, 2022; Haramboure et al, 2020; Pleydell and Bouyer, 2019). Models suggest large dependence on the biological features of the host species and the type of mortality agent employed.…”

Section: Introductionmentioning

confidence: 99%

Sex-specific sub-lethal effects of low virulence entomopathogenic fungi may boost the Sterile Insect Technique

Duneau,

Gallet,

Adhiambo

et al. 2024

Preprint

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BACKGROUND: The Sterile Insect Technique (SIT) is a species-specific method for controlling insect pests. Recent studies have explored the combination of SIT with entomopathogenic microorganisms, known as boosted-SIT, to enhance its effectiveness. This study aimed to evaluate the potential of the entomopathogenic fungi, Metarhizium anisopliae, in boosting the SIT for managing the oriental fruit fly, Bactrocera dorsalis. METHODS: Adult flies from a laboratory population of B. dorsalis were inoculated with one of eight strains of M. anisopliae to assess fungus virulence in each sex. Ideally, boosted-SIT should minimally impact sterile males and reduce female fecundity maximally. A brief exposure to fungal spores was efficient to infect males, and for them to transmit the fungus to females when hosted together for 24 hours. RESULTS: Our results showed significant variations in the mortality induced by the strains in males, but not in females that exhibited low mortality. Strains varied in their sub-lethal effects on female fecundity, with almost a two-fold variation among strains. Furthermore, strains that had the lowest virulence on males tended to reduce female fecundity the most. CONCLUSION: Our study brings a proof of concept that it is possible to leverage boosted-SIT using carefully selected pathogen strains and their sub-lethal effects on both the male and female fruit fly.

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“…Therefore, the design of innovative based, for example, entomovection such as auto-inoculation of wild flies in the field (Faye et al 2021, Stafford 2017) or the release of mass-reared sterile males (in the framework of Sterile Insect Technique [SIT] programs,) as vectors of micro-doses of biocides to wild flies of the same species (Bouyer and Lefrançois 2014, Diouf et al 2022), open new avenues for more sustainable strategies for fruit fly management. The latter technology, named ‘boosted SIT’, has shown some potential in coffee-growing areas in Guatemala where the release of C. capitata sterile males coated with fungal spores of Beauveria bassiana resulted to spore transmission to 44% of the captured wild males (Flores et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Dose, temperature and formulation shapeMetarhizium anisopliaevirulence against the oriental fruit fly: lessons for improving on-target control strategies

Chailleux,

Coulibaly,

Diouf

et al. 2023

Preprint

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Entomopathogenic fungi are a promising tool for the biological control of crop pests provided low or no impact on non-target organisms. Selection for host specificity as well as on-target applications open new avenues for more sustainable strategies for pest management. Isolates ofMetarhizium anisopliae(Metschn.) Sorokin have been identified as promising for developing innovative entomovection-based strategies for the control of the oriental fruit fly,Bactrocera dorsalis(Hendel) (Diptera: Tephritidae), in Africa. To be effective, this technology requires high strain virulence at a low number of spores, in field conditions, but sufficient incubation time to allow transmission to wild conspecifics.In the present study, we investigated the virulence of the Met69 OD strain against adult flies, depending on the inoculation dose, formulation and air temperature. High pathogenicity was observed at very low inoculation doses (LT50 of 4.85 days with 6100 spores per fly) independently of fly sex. Virulence increased with spore load in a tight range (5600 and 6100 spores per fly) and with air temperature observed in the field (20-28°C). Unexpectedly, corn starch used as an adjuvant to increase the carrying capacity of insects decreased the virulence of the pathogen.Results are of utmost importance to improve area-wide control strategies based on contamination of wild flies in mango orchards through auto-inoculation devices or interactions with released mass-reared sterile males coated with fungal spores.

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An agent-based model to simulate the boosted Sterile Insect Technique for fruit fly management

Cited by 16 publications

References 76 publications

The Fallacy of Year-Round Breeding in Polyphagous Tropical Fruit Flies (Diptera: Tephritidae): Evidence for a Seasonal Reproductive Arrestment in Bactrocera Species

The Fallacy of Year-Round Breeding in Polyphagous Tropical Fruit Flies (Diptera: Tephritidae): Evidence for a Seasonal Reproductive Arrestment in Bactrocera Species

Sex-specific sub-lethal effects of low virulence entomopathogenic fungi may boost the Sterile Insect Technique

Dose, temperature and formulation shapeMetarhizium anisopliaevirulence against the oriental fruit fly: lessons for improving on-target control strategies

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