Insecticidal effects of essential oils against wooly beech aphid, Phyllaphis fagi (Hemiptera: Aphididae)and rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae)
Aurash R. Yazdgerdian, Yasmin Akhtar, Murray B. Isman
Eleven essential oils (Citrus aurantium, Citrus sinensis, Citrus limon, Eugenia uniflora, Ocimum gratissimum, Rosmarinus officinalis, Gaultheria procumbens, Thuja plicata, Pseudotsuga menziesii, Abies grandis, Bursera graveolens) were tested against Phyllaphis fagi, as contact and residual toxins. Abies grandis (LC50=0.006%) was significantly the most active contact toxin followed by the positive control, R. officinalis (LC50=0.134%), P. menziesii (LC50 = 0.428%), B. graveolens (LC50=0.907%), and T. plicata (LC50=1.011%). Five of these essential oils were also tested against Sitophilus oryzae for fumigation effects. Based on the LC50 values of the oils, G. procumbens was the most active fumigant (LC50=6.8ul/l air). Thuja plicata and B. graveolens oils were equitoxic. Rosmarinus officinalis and A. grandis were the least toxic(LC50=53.6 and 38.6 ul/l air respectively). In grain-treated bioassay against S. oryzae, G. procumbens was the most active (LC50=0.235 µl-g-1) followed by R. officinalis. Thuja plicata and B. graveolens were equitoxic. Abies grandis was the least toxic. These oils exhibit different modes of action and have potential to be used as commercial insecticides against P. fagi and S. oryzae.