Demand-Driven Technologies for Sustainable Maize ... - IITA

287Table 1. Insecticidal effects by contact of essential oils from O. gratissimum,P. nigrum and X. aethiopica on S. zeamais at concentrations of5 and 10%.Exposure time (hours)48 96Concentrations (%)Essential oils 5 10 5 10O. gratissimum 66.1 ± 5.8 76.9 ± 5.0 85.9 ± 6.9 85.7 ± 5.3P. nigrum 88.5 ± 6.8 95.6 ± 5.0 92.7 ± 5.8 97.2 ± 4.6X. aethiopica 71.4 ± 6.4 86.8 ± 5.9 85.0 ± 4.7 90.1 ± 6.7Control (actelic) 59.7 ± 3.1 69.8 ± 2.9 75.5 ± 2,2 83.1 ± 1.9Table 2. LD 50calculated for mortality after 96 hours of exposure of S.zeamais Motsch to essential oils of O. gratissimum, X. aethiopicaand P. nigrum.Essential oils Ingestion ContactO. gratissimum 75.15 48.55X. aethiopica 83.19 45.59P. nigrum 16.95 22.89For all the plant materials tested, the results of probit analysis(Table 2), which determined LD 50, showed that the mortality ratesobtained by consumption were higher than those obtained by directapplication. The implication of this is that lower concentrations ofessential oil will be more effective by contact than by ingestion. Thecontact test is, therefore, more effi cient than the ingestion test in thecontrol of S. zeamais. Moreover, statistical analysis showed that therewas a signifi cant difference (P