Acaricidal and sublethal effects of tobacco leaf and garlic bulb extract and soft soap on Tetranychus urticae Koch. (Acari: Trombidiformes: Tetranychidae)

Abstract

The ovicidal, adulticidal and fecundity effects of tobacco (Nicotiana tabacum L.) leaf extract, garlic (Allium sativum L.) bulb extract, soft soap and their binary mixtures were investigated against Tetranychus urticae Koch. (Trombidiformes: Tetranychidae) eggs and adult females under controlled conditions [25 degrees C +/- 1, 65 +/- 5% R.H. (mean +/- SD) and a photoperiod of 16L: 8D (Light: Dark)]. The concentrations used for the ovicidal and adulticidal effect were chosen after preliminary bioassays to obtained mortality rates equally distributed between 0%-100%. However, one concentration giving around 50 % percent adult mortality of each compound was tested for fecundity effect. Each stock solution was diluted separately with distilled water to give the desired different concentrations of each extract. The results showed that the tobacco leaf extract, the soft soap and the garlic extract+soap mixture were the most toxic against adult females. Although the garlic bulb extract had the lowest toxic effect, its mixtures with the soft soap and tobacco extract showed higher toxicity against the adults. Moreover, the tobacco application at the tested dose significantly reduced the T. urticae fecundity. It is also determined that the tobacco leaf and garlic bulb extracts have potential to be used in the control of T. urticaeeggs. On the other hand, the ovicidal activity of soft soap can be increased by addition of the garlic extract. However, further investigation is needed to assess their phytotoxicity under greenhouse and field conditions. The efficacy of these compounds to natural enemies should also be measured.