Effect of a horticultural mineral oil on oviposition by two-spotted mite Tetranychus urticae Koch (Acari: Tetranychidae)

The impact of spray deposits of an nC24 horticultural mineral oil on two-spotted mite oviposition on French bean leaf discs was evaluated under laboratory conditions. An unsprayed control was compared with 25, 50, 100 and 150 µg cm-2 deposits of oil sprays applied with a Potter spray tower. One day after adult female mites were placed on untreated and treated leaf discs significantly fewer eggs were recorded on discs treated with 100 and 150 µg cm-2 deposits. Significant differences between all oil treatments and the untreated control were found 2 d and 6 d after females were placed on the discs, and the number of eggs laid on oil treated discs fell as the concentration of oil in sprays increased. The relationship between the number of eggs per leaf disc and oil concentration on day 6 was a typical negative exponential