Essential oils as prospective fumigants against Tetranychus urticae Koch

The efficacy of essential oils (EOs) obtained from 18 aromatic plant species against Tetranychus urticae, an important pest of greenhouse crops, was studied under in vitro conditions. The EOs were applied by fumigation in a highest tested concentration of 15 mu l L-1. Based on the comparison of lethal doses, the most efficient EO was selected, obtained from Ocimum basilicum (LC50 = 0.6 mu l L-1; LC90 = 5.9 mu l L-1). Females found in an area, with EO fumes laid significantly fewer eggs compared to the control. Oviposition was most inhibited by the fumes of EOs from Ocimum basilicum, Mentha spicata, M. arvensis, M. pulegium, Origanum majorana, and Origanum compactum, which showed fertility inhibition higher than 80%. Short-term exposure of eggs to the fumes of some EOs caused their high mortality. The highest ovicidal effect was observed for the EO obtained from M. spicata (LC50 = 0.3 mu l.L-1; LC90 = 1.7 mu l L-1). A comparison of the biological efficacy and chemical composition of the EOs revealed that EOs containing a major share of oxygenated monoterpenes had much higher activity. Based on the results of acute and ovicidal toxicity, EOs obtained from M. spicata and O. basilicum, including their major compounds, linalool and carvone, were selected as active substances suitable for the development of botanical acaricides applied by fumigation. (C) 2016 Elsevier B.V. All rights reserved.