Entomopathogenic Fungi as Endophytes for Biological Control of Subterranean Termite Pests Attacking Cocoa Seedlings.

Chaba F Ambele,Hervé D B Bisseleua,Olubukola O Babalola,Fathiya M Khamis,Komivi S Akutse,Sunday Ekesi,Christian T L Djuideu

doi:10.3390/jof6030126

Abstract

This study was conducted in the scope of developing a sustainable effective approach against subterranean termite pests using entomopathogenic and endophytic fungus-based biopesticides. Termites, Odontotermes spp. workers, were tested for their susceptibility to 15 entomopathogenic fungal isolates through the direct spraying of conidia suspensions at 1 × 108 conidia/mL. In general, all the isolates screened were pathogenic, with 100% mortality 4–7 days post-inoculation. However, the most virulent isolates were Metarhizium brunneum Cb15-III; the M. anisopliae isolates ICIPE 30 and ICIPE 60; Hypocrea lixii F3ST1; and the Beauveria bassiana isolates ICIPE 279, ICIPE 706 and ICIPE 662. These isolates were further tested for their endophytic colonization of cocoa seedlings using seed soaking, soil drench and foliar spray at 1 × 108 conidia/mL. The colonization of the plant tissues by the fungi was determined using a culture-based technique. Only the B. bassiana isolates ICIPE 706 and ICIPE 279, and H. lixii F3ST1 colonized the cocoa seedlings, with varied colonization rates among isolates and inoculation methods. Three naturally occurring endophytes—Trichoderma asperellum, Fusarium solani and F. redolens—were also isolated from the cocoa seedling tissues. These findings suggest that cocoa seedlings are conducive to endophytic fungal growth either occurring naturally or from artificial inoculation Our findings could possibly lead to an innovative approach to the management of herbivory and subterranean termite pests in cocoa agroforests.

Highlights

Termites are becoming major pests in cocoa agroforests, causing significant losses [1,2,3,4].Their control in the past relied on persistent organochlorine insecticides [5], which are under restrictive use due to increasing concerns over negative effects on human and environmental health.Farmers in many parts of Africa use various traditional termite control methods, often with limited success [2]
The sterilized cocoa seeds were soaked for 12 h in a conidial suspension of 1 × 108 conidia/mL prepared from the most virulent isolates (M. brunneum Cb15-III; Hypocrea lixii F3ST1; M. anisopliae ICIPE 30 and ICIPE 60; and B. bassiana ICIPE 279 and ICIPE 706), obtained from the above pathogenicity bioassay
Our results show that only B. bassiana isolates ICIPE 279 and 706, and H. lixii F3ST1 could successfully colonize and establish in cocoa seedlings as endophytes without causing any visual/visible symptoms or damage to the seedlings like in the control treatments

Summary

Introduction

Termites are becoming major pests in cocoa agroforests, causing significant losses [1,2,3,4].Their control in the past relied on persistent organochlorine insecticides [5], which are under restrictive use due to increasing concerns over negative effects on human and environmental health.Farmers in many parts of Africa use various traditional termite control methods, often with limited success [2]. Termites are becoming major pests in cocoa agroforests, causing significant losses [1,2,3,4]. Their control in the past relied on persistent organochlorine insecticides [5], which are under restrictive use due to increasing concerns over negative effects on human and environmental health. Farmers in many parts of Africa use various traditional termite control methods, often with limited success [2]. There is, a need for the identification of sustainable eco-friendly and locally available alternative methods for termite control in cocoa agroforests.

Methods

Results

Discussion

Conclusion