Insecticide activity and toxicity of essential oils against two stored-product insects

The weevils Sitophilus oryzae L. and Sitophilus zeamais Motsch. are stored-product pests that are mainly controlled with synthetic insecticides. Insecticides made from essential oils (EOs) from bioactive plants can provide alternative control options that are safer and less environmentally damaging. This study investigated the chemical composition and insecticide activity of the EOs of Tagetes minuta L., Baccharis uncinella DC, Baccharis dracunculifolia DC, Salvia officinalis L., Mentha arvensis L., and Melaleuca alternifolia C. against S. oryzae and S. zeamais. The number of compounds we identified in the EOs studied ranged between 10 for T. minuta and 21 for B. uncinella. Only the EOs of T. minuta and M. arvensis showed insecticidal activity. Fumigation was more effective than the contact method for both EOs. The EO of M. arvensis had the highest level of toxicity in the contact method, with an LC50 of 71.58 μL/L for S. oryzae and 67.31 μL/L for S. zeamais. It also had the highest toxicity in the fumigation method (LC50 of 56.41 μL/L for S. oryzae and 47.03 μL/L for S. zeamais) with the lowest lethal time (LT50 of 8.9 h for S. oryzae and 8.1 h for S. zeamais). The EO of M. arvensis, therefore, has the greatest potential for development as a new botanical insecticide for the control of stored-product adult weevils. •Only the essential oils (EOs) of Tagetes minuta and Mentha arvensis showed satisfactory insecticide activity against weevils.•The fumigation method showed higher toxicity than the contact method for both pest species.•The EO of M. arvensis was more effective as an insecticide over a shorter period.•The EO of M. arvensis is effective in the control of stored-grain pests.