Date of Award


Degree Name

MS in Agriculture - Plant Protection Science


Horticulture and Crop Science


Michael J. Costello


Willamette mite (WM), Eotetranychus willamettei, is a major pest throughout most winegrape regions in coastal California and Oregon. These mites puncture leaf tissue with their chelicerae and cause loss of photosynthetically active area. Chemical control treatments on grape include nearly ten registered synthetic miticides, plus soaps and oils. Oils can be petroleum based (mineral oil) or botanical (from seeds of various plants). There has been a lot of interest of late in the use of botanical oils other than soybean, including those derived from the seeds of plants including spearmint, rosemary and clove. This project tested for differences in the efficacy of a mineral vs. a botanical oil. The botanical oil was a blend of rosemary and peppermint oil (Ecotrol®) and was tested against a petroleum based oil (Omni Oil®), then compared to a commonly used synthetic miticide (Nexter®, common chemical name pyridaben). The field experiment (San Juan Vineyards in Shandon, CA) tested effects on adult mite and egg populations, with five treatments: Omni Oil®, Ecotrol®, Nexter®, Ecotrol® + Nexter®, and water as a control. Laboratory experiments tested effects on adult females and eggs. Treatments were Omni Oil®, Ecotrol® (1.0%), Ecotrol® (0.5%) and water as a control. Field data showed that Omni Oil® (at 1.5%) was the only effective treatment, Ecotrol® (at 0.5% or 1.0%) did not differ from the control. Omni Oil® was the most effective treatment against adult mites in the laboratory studies, followed by Ecotrol® at 1.0%, with Ecotrol® at 0.5 % not very effective. Egg mortality was high with Omni Oil® 1.5% or Ecotrol® 1.0% but low with Ecotrol® 0.5%.

Included in

Entomology Commons