EVALUATION OF SOME DICOTYLEDONOUS SEED EXTRACTS AGAINST COCONUT LEAF BEETLE, BRONTISPA LONGISSIMA (GESTRO) (COLEOPTERA: CHRYSOMELIDAE) AND SUBLETHAL EFFECT TO AN ENDOPARASITOID

Abstract

Aqueous and ethanolic seed extracts of Annona squamosa L. and Mangifera altissima B. were evaluated in the laboratory on adult coconut leaf beetles, Brontispa longissima G. Direct-spray method was employed in delivering the treatments to the test beetles. On the other hand, dip method was used in exposing parasitized pupae to different treatments. Laboratory results revealed that aqueous and ethanolic extracts of M. altissima at 15% w/v and 10% w/v, respectively and A. squamosa at 2%w/v and 10%w/v, correspondingly were comparable to Thiametoxam™. Percentage mortalities observed for all seed extracts used except the aqueous form of M. altissima exhibited a dose-dependent manner. Probit analysis revealed that the trend for LC50 for each seed extracts is M. altissima aqueous extracts (MAAE) >A. squamosa aqueous extracts(ASAE) >M. altissima ethanolic extracts (MAEE) >A. squamosa ethanolic extracts (ASEE). It was also found that based on recorded mean parasitoid emergence, Thiametoxam™ had greater sub-lethal effect than the botanicals on the natural enemy of coconut leaf beetle, Tetrastichus brontispae F. (5.00 ± 3.00). The chemical groups such as phenols, saponins and tannins might be possibly responsible for the observed bioactivities against the hispid beetle. UV-vis analyses of ethanolic fractions further revealed presence of secondary metabolite known to have several biological activities; annonasquacin for A. squamosa and mangiferin for M. altissima. Proper formulation of these materials can be developed as alternative control to B. longissima as they may offer selectivity than conventional insecticide and contain mixture of phytochemicals that can deter development of insect resistance.