Toxicity of Some Pesticides against Oligonychus afrasiaticus (Mcgregor) (Acari: Tetranychidae) in Tunisian Oases and Analysis of Their Residues in Date Fruits

Background: In Tunisia, the date palm mite Oligonychus afrasiaticus McGregor (Acarina: Tetranychidae) is one of the most important pests of the date palm Phoenix dactylifera L. (Arecaceae). The control of Oligonychus afrasiaticus in Tunisian oases requires the use of safe and effective acaricides. Methods: In this study, the toxicity of pesticides (sulfur, hexythiazox, bifenazate and spinosad) against O. afrasiaticus in date palms was investigated in the field. The aim of this study was also to evaluate the dissipation of bifenazate, hexythiazox and spinosad in date fruits by the QuEChERS method. Result: Bifenazate was effective with a reduction of 90.2 and 89.4% of O. afrasiaticus motile forms and eggs, respectively, up to 21 days after application of this insecticide. Within 21 days of spraying, hexythiazox was an effective acaricide, reducing eggs and motile forms to 98.5% and 82.5%, respectively. Spinosad was effective for up to 14 days. Under the conditions of the Tunisian oases, the sulfur toxicity applied in July may remain effective for less than 14 days after treatment. Regarding, the dissipation of tested pesticides, the results showed that bifenzate deposited faster in date fruits than hexythiazox and spinosad. The initial deposition of bifenzate and spinosad decreased and was no longer detected after 7 and 14 days, respectively. Hexythiazox was detected at harvest when the date fruits were treated twice, but the residues were lower than the residue levels recommended by the European Union. These results would be useful to improve the control of O. afrasiaticus based on the efficacy, persistence and toxicity of these pesticides.