Comparative efficacy of two plant extracts and cypermethrin against field insect pests of Amaranthus hybridus L.

Abstract

Abstract. Insect infestations are major constraints to vegetable production in Nigeria causing low yields and poor quality of produce. A study was conducted at the experimental farm of the National Horticultural Research Institute (NIHORT) Ibadan, Nigeria, to compare the efficacy of ethanol seed extracts of Azadirachta indica A.Juss (neem), Annona muricata L(soursop) and cypermethrin against field insect pests of Amaranthus hybridus L. under rain fed conditions. Four major insect species were observed causing damage to A. hybridus during the study and they include: cotton bollworm (Heliothis armigera Hubner), okra leaf roller (Sylepta derogata Fabricius), lagriid beetle (Lagria villosa Fabricius) and variegated grasshopper (Zonocerus variegatus Linnaeus). Ethanol seed extracts of A. indica were as effective as cypermethrin and more effective than A. muricata seed extracts in protecting A. hybridus against insect damage. Plots treated with A. indica extracts and cypermethrin significantly (p<0.05) reduced leaf damage, observed insect density and enhanced leaf yield compared to plots treated with A. muricata and control. There was no significant difference (p>0.05) between A. indica and cypermethrin treated plots on observed insect density, leaf damage and leaf yield. A. indica has proved to be efficient as cypermethrin and can be successfully used for the control of field insect pests of A. hybridus.