Control of cocoa mirids using aqueous extracts of Thevetia peruviana and Azadirachta indica

Serge Bertrand Mboussi,Stéphanie Kakam,Leïla Bagny Beilhe,Zachée Ambang,Manuel Tejada Moral

doi:10.1080/23311932.2018.1430470

Abstract

Mirids, Sahlbergella singularis, are the most harmful cacao pest in Africa. Chemical management, although controversial, is currently the only effective option for controlling these pests. Based on in vitro and field experiments, this study evaluated and compared the effectiveness of aqueous extracts obtained from the seeds of Thevetia peruviana (TP) and Azadirachta indica (AI) in controlling cocoa mirids, S. singularis. Thevetia peruviana extracts proved to be more effective than A. indica extracts and were as effective as Actara 25 WG, the benchmark insecticide, in reducing mirids in the field. All the aqueous extracts tested in vitro displayed insecticidal activities within maximum eight days and some repellent effects at both 10 and 25% w/v. Treatment of mirid food with the extracts also led to high mortality rates and to significant avoidance of pods treated with the TP25, TP10 and AI25%. The use of plant aqueous extracts to control mirids in the field thus offers promising prospects for the control of this pest, given the availability of the plants, their simple preparation, their effectiveness and their eco-friendly features.

Highlights

Worldwide cocoa production is currently four million tons per year, of which 72% comes from Africa (Ivory Coast, Ghana, Nigeria and Cameroon) (ICCO, 2016)
In this study, Thevetia peruviana and A. indica aqueous extracts were as effective as Actara®25 WG, the benchmark insecticide, in reducing mirid populations in the field
The effectiveness of these aqueous extracts shows them to be a viable option for smallholders who are in need of an accessible, less expensive and more environmentally friendly control method

Summary

Introduction

Worldwide cocoa production is currently four million tons per year, of which 72% comes from Africa (Ivory Coast, Ghana, Nigeria and Cameroon) (ICCO, 2016). The work presented here is part of the research program of the Department of Biology and Vegetal Physiology of the Faculty of Science of the University of Yaoundé, Cameroon. This research program conducted by Pr Zachée Ambang, aims at developing biopesticide to control pest and disease of agricultural crops mainly cocoa. In this lab, crude extracts derivated from local plants (Azadirachta indica, Thevetia peruviana) are tested against many insects’ pests and pathogens (nematodes: Meloidogyne sp, Glomus sp, fungus: Cercospora sp, stramenopile: Phytophthora sp) responsible for main losses in crop production.

Objectives

Methods

Results

Conclusion