Effectiveness of some ecological pest management practices against the brown cocoa mirid, Sahlbergella singularis (Hemiptera: Miridae) in Nigeria

Abstract

Sahlbergella singularis, the brown cocoa mirid, is the most economically important insect pest of cocoa in West Africa, capable of causing over 70% yield loss. The use of synthetic insecticides over the years has led to serious health and environmental issues making research into ecologically sound alternatives inevitable. This study therefore highlights pest management tools that have been developed for the effective control of mirids with minimal deleterious effects on the ecosystem. Cultural control practices involving pruning of chupons, timely phytosanitation and removal of mummified pods were carried out on treated cocoa plots and mirid infestation levels were compared to untreated plots. Field evaluation for resistance was conducted on 44 cocoa genotypes by assessing mirid damage on cocoa as indicated by lesions on pods, twig dieback and cankers of trunks. The predatory efficiency of seven different ant species was conducted on the mirids. Population of mirids in treated plot reduced by 6.2 times. Some international cocoa genotypes (EET59, Ven-C4, UF676, Amaz15-15, BE10, Mocorongo and Pa107) showed high resistance to mirids with very low damage scores whereas the local genotype N38 was highly susceptible to mirid damage in terms of lesions, dieback and canker with mean scores of 2.61, 1.85 and 2.77, respectively. The ant species exhibited varying degree of predation in the laboratory. Oecophylla longinoda, Acantholepis capensis and Camponotus acvapimensis caused 100%, 50.5% and 35% mortalities of mirids in the laboratory, respectively. Ecological pest management tactics offer safe, effective and environmentally friendly control against this obnoxious insect pest of cocoa.

Keywords: Sahlbergella singularis, cultural control practices, cocoa genotypes, ant species.