Prospects of botanical pesticides in management of Iroko gall bug, Phytolyma fusca (Hemiptera, Psylloidea) under laboratory and field conditions

Abstract

Abstract Background Iroko gall bug, Phytolyma fusca Walker, is a major insect pest of Milicia excelsa (Iroko) seedling hampering its propagation in West Africa. Milicia excelsa is an indigenous forest timber tree in the tropical rain forest of West Africa with a very high value in international trade due to its wood quality. Sustainable management of P. fusca infestations on Iroko seedlings have not been achieved due to their cryptic nature and multivoltine generations. This study evaluated the residual and contact effects of crude ethanol and aqueous extracts of four plants (Azadirachta indica, Jatropha curcas, Piper guineense, and Aframomum melegueta) on adult P. fusca in the laboratory and field. Results All the extracts had residual effects and contact effects on adult insects in the laboratory at 75% and 100% concentrations of applications. Azadirachta indica, P. guineense, and A. melegueta gave 80–100% adult mortality at both concentrations in the laboratory; their efficacies were comparable to cypermethrin. The ethanol extracts of P. guineense and A. indica were more effective than other extracts in protecting the seedlings against Phytolyma infestations in the field. They significantly (p < 0.01) reduced infestation compared to other extracts and control. Ethanol extracts of the tested plant materials were more effective than their aqueous extracts both in the laboratory and field. Conclusion The results proved that P. guineense and A. indica extracts were very potent and promising in protecting Milicia excelsa seedlings against Phytolyma fusca infestations and they can be used in the early management of Phytolyma infestations in the field.