The toxicity of herbicides and repellency of fluvalinate to the gorse mite Tetranychus llnteartus Dufour (Acari: Tetranychidae): A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticultural Science with Honours in the University of Canterbury

Abstract

The toxicity of four herbicides and four surfactants to adult female gorse mites (Tetranychus lintearius Dufour) was investigated in laboratory studies. The herbicides were triclopyr, triclopyr plus picloram, glyphosate, and metsulfuron. The surfacants were Silwet L-77, Triton X-45, Agral LN and Citowett. All herbicide and surfactant combinations except metsulfuron with either Triton X-45, Agral LN or Cittowett were found to be toxic to gorse mites. The toxicity and repellency of fluvalinate to adult female gorse mites was also determined. Field rate of fluvalinate (0.1 g ai/l) caused 80% mortality of gorse mites using slide dip tests. Fluvalinate was repellent and caused adult female gorse mites to run-off treated surfaces. The greatest colonisation of untreated surfaces resulted when gorse shoots were treated with 0.001 g ai/l of fluvalinate. The potential for using herbicides or fluvalinate in integrated gorse control is discussed.