Maize is one of the most important staple foods in sub-Saharan Africa. Optimum maize yield has not been attained in many places because of serious damage caused by lepidopterous stem borers which are major insect pests limiting maize production. Sesamia calamistis is one of the stem borer species abundant in Nigeria. Use of synthetic insecticides to control these pests has been practiced overtime, but has been limited by its toxicity to mammals and the ecosystem at large. An alternative means of control with the use of plant extracts has been recently emphasized. This study was carried out to determine the insecticidal efficacy of Tithonia diversifolia extracts against Sesamia calamistis. Maize variety, BR 9943 DMRSR (white) was planted and later infested with blackhead stage egg batches of Sesamia calamistis 3 weeks after crop emergence. Twenty per cent aqueous leaf extract of Tithonia diversifolia was applied 1 week after artificial infestation. Carbofuran 3G (1g/plant) was used as a standard check treatment and untreated plants were included as controls. Application of the plant extracts, markedly reduced stem tunneling, stem breakage, dead heart formation, exit/entry holes and number of emerged larvae in treated plants. Plant heights at 2 and 4 weeks after infestation were also maintained positively in treated plants. In terms of plant height, plants treated with aqueous leaf extract of Tithonia diversifolia showed significant difference, showing that Tithonia diversifolia can be incorporated in organic farming as well as Integrated Pest Management (IPM). Tithonia diversifolia plant extract is encouraged for use as an alternative to carbofuran in the control of Sesamia calamistis.
Key Words: Optimum, Synthetic, Efficacy, Tunneling, Tithonia diversifolia extract