Interactions between the predatory mite Typhlodromalus aripo and the entomopathogenic fungus Neozygites tanajoae and consequences for the suppression of their shared prey/host Mononychellus tanajoa.

Bonaventure Vidjannagni Agboton,Alexis Onzo,Stefan Vidal,Andreas Von Tiedemann,Rachid Hanna

doi:10.1007/s10493-012-9630-1

Bonaventure Vidjannagni Agboton, Alexis Onzo + Show 3 more

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https://doi.org/10.1007/s10493-012-9630-1

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Abstract

The predatory mite Typhlodromalus aripo and the entomopathogenic fungus Neozygites tanajoae, both introduced from Brazil for control of the cassava green mite (CGM) Mononychellus tanajoa, now co-occur in cassava fields in Benin. However, studies on interactions between these two natural enemies and how they might affect CGM biological control are lacking. We determined in screenhouse experiments the effects of single and combined releases of N. tanajoae and T. aripo on CGM suppression. In the single natural enemy treatment, both T. aripo and N. tanajoae significantly reduced CGM densities, but the results of the predator (T. aripo) are more quickly measurable than those of the pathogen (N. tanajoae) in our short-term experiment. The level of CGM suppression in the combined natural enemy treatment was reduced considerably compared with T. aripo-alone, but only slightly when compared with N. tanajoae alone, with a simultaneous reduction in T. aripo and N. tanajoae abundance or prevalence. In a laboratory experiment, T. aripo fed more on N. tanajoae-infected CGM than on healthy CGM and its oviposition and survival were reduced when fed on the former compared with the latter, which can help in explaining the reduction in numbers of T. aripo and consequently the considerable loss in suppression of CGM in the combined natural enemy treatment in the screenhouse experiment. Together, the screenhouse and the laboratory experiments predicted negative interactions between the two natural enemies with negative consequences for CGM biological control. Long-term field observations and rigorous field experiments that simultaneously manipulate T. aripo and N. tanajoae abundance and prevalence are needed to validate the prediction of this study.

Highlights

The relative benefits of introducing single or multiple natural enemy species for classical biological control has long been debated by ecologists and biological control practitioners (Polis et al 1989; Sih et al 1998; Losey and Denno 1999; Gnanvossou et al 2003; Onzo et al 2004; Sabelis et al 2009)
Interactions between natural enemies are relevant to classical biological control of the cassava green mite (CGM), Mononychellus tanajoa (Bondar) (Acari: Tetranychidae), in Africa, because this pest is attacked by several natural enemies
The addition of N. tanajoae—main pathogen effect—had little effect on overall CGM densities (Fig. 1a; Table 1). This may be explained by the time take by the pathogen to develop infection and contaminate healthy mites. This is supported by the strong interaction between T. aripo addition and N. tanajoae addition. (Table 1), which necessitated the examination of simple effects for partitioning direct and indirect effects of N. tanajoa or T. aripo addition on CGM densities

Summary

Introduction

The relative benefits of introducing single or multiple natural enemy species for classical biological control has long been debated by ecologists and biological control practitioners (Polis et al 1989; Sih et al 1998; Losey and Denno 1999; Gnanvossou et al 2003; Onzo et al 2004; Sabelis et al 2009). The lack of predator persistence in some agroecologies and lack of predator colonization of glabrous varieties necessitated the search for a complementary approach to enhance CGM biocontrol in areas where it has not been fully achieved by exotic phytoseiid predators In this regard, Brazilian isolates of the entomopathogenic fungus Neozygites tanajoae (Entomophthorales: Neozygitaceae), known to be virulent to CGM (Delalibera et al 1992) and to be specific to this pest (Hountondji et al 2002a; Agboton et al 2009b), were introduced into Africa where they were evaluated in the laboratory and later tested in cassava fields in southern Benin (Hountondji et al 2002b). In some regions (e.g., Benin in West Africa), T. aripo and N. tanajoae share the same cassava fields but presently data on the combined effects of this T. aripo and fungus on control of CGM is lacking

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