Parasitoid control of the tomato fruitworm, Helicoverpa armigera, in smallholder farmer fields in Senegal

ABSTRACT

In Africa, Helicoverpa armigera (Hübner) (Lepidoptera, Noctuidae) is a key pest of cotton and vegetable crops, particularly tomato. Alternatives to insecticides to control this pest are needed such as conservation biological control. However, knowledge on the diversity and ecology of naturally occurring enemies of H. armigera is limited. A two-year field survey was conducted in a set of tomato farmer fields in the main vegetable-growing area in Senegal (Niayes) to assess the spatial and seasonal occurrence of indigenous parasitoids of H. armigera, and to evaluate the effect of insecticide use on biological control efficiency. No parasitoid emerged from H. armigera eggs. Incidence of larval parasitoids was generally moderate (20%) but highly variable (0%–100%) among fields, independently of host abundance, and negatively affected by the number of insecticide applications. Larval parasitism was largely dominated by the larval parasitoid Meteorus laphygmarum Brues (Hymenoptera, Braconidae), but a positive correlation was found between specific richness or Shannon diversity index of the parasitoid community and parasitism rate. This study is a first step toward development of research and extension programs for conservation of natural enemies in the framework of integrated management of the tomato fruitworm in Senegal.

KEYWORDS:

• Conservation biological control
• parasitoid diversity
• insecticide use
• Old World bollworm
• integrated pest management
• Africa

Acknowledgments

We express our sincere gratitude to G. Delvare (CIRAD, Montpellier, France) for identification of parasitoid species. This study would not have been carried out without the technical assistance of O. Ndoye (FPMN, “Fédération des Producteurs Maraîchers de la zone des Niayes”), S. Sylla and E. Tendeng (Master students). We thank E.V. Coly (DPV, Senegal) for supporting our work and we are grateful to anonymous reviewers for their comments and helpful suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by IRD (AIRD) [grant number PEERS-BIOBIO-2013] and West Africa Agricultural Productivity Program (WAAPP).