Abstract
The toxicity of glyphosate and metribuzin on five species of soil-dwelling predatory mites, Lasioseius dentatus (Fox) (Acari: Ascidae), Androlaelaps casalis (Berlese) (Acari: Laelapidae), Rhodacarus roseus (Oudemans) (Acari: Rhodacaridae), Macrocheles muscaedomesticae (Scopoli) (Acari: Macrochelidae) and Cunaxa setirostris (Hermann) (Acari: Cunaxidae) was evaluated under laboratory conditions. Three different concentrations (half of the recommended dose (HRD), recommended dose (RD) and double the recommended dose (DRD)) of both herbicides were tested. All soil-dwelling predatory mites under study showed high susceptibility to both herbicides, demonstrating that they can significantly reduce the population of all five species of soil-dwelling predatory mites. HRD of glyphosate can reduce the population of all five species of soil-dwelling predatory mites by > 50%, except C. setirostris, as its mortality was 30%, whereas HRD of metribuzin can only reduce the population of L. dentatus and M. muscaedomesticae by > 50%. Obviously, glyphosate seems to be more toxic to all five species of soil-dwelling predatory mites than metribuzin. L. dentatus was found to be the most sensitive soil-dwelling predatory mite, whereas C. setirostris was found to be the least sensitive to both herbicides, as well as a control (well water), compared with all the tested soil-dwelling predatory mites.
Finally, the highest mortality rates (100%) were obtained for DRD of both herbicides. Therefore, extra care and serious caution must be exercised when diluting and applying these herbicides to ensure their RD is never exceeded as they can kill all soildwelling predatory mites studied here in significant numbers, which leads to a sharp reduction in their populations as well as a reduction in their role in the ecological balance.