The transfer of Typhlodromus pyri on grape leaves for biological control of Panonychus ulmi (Acari : Phytoseiidae, Tetranychidae) in vineyards in Ontario, Canada

The phytophagous mite Panonychus ulmi Koch has become a significant problem in Ontario vineyards. We attempted to introduce and establish populations of the predatory mite Typhlodromus pyri Scheuten for P. ulmi biological con trol. Grape leaves were transferred from a vineyard containing T. pyri in e arly summer 1998, by picking leaves from a donor vineyard and attaching the m onto leaves in the release vineyard where T. pyri were extremely rare. Tw o release treatments were used with rates of 8.5 (1x) and 25.5 (3x) mobiles per vine. In the first season, T. pyri established in similar densities in both release treatments, which were significantly higher than controls. Ho wever, there were no differences among treatments in P. ulmi densities in 1 998 as a result of predator release. During summer 1999, significantly fewe r P. ulmi mite days were observed in release plots compared to the control. Amblyseius fallacis (Garman) was common throughout the release vineyard in 1998 and in 1999, but appeared on the vines too late in the season to main tain low P. ulmi densities. T. pyri appeared to out compete A. fallacis in 1999 because A. fallacis densities were significantly lower in plots where T. pyri had been released than in control plots. We conclude that T. pyri c an be effective for P. ulmi biological control in Ontario vineyards and may be introduced by transferring leaves. In Europe, transferring prunings has been the standard method of inoculating T. pyri into new vineyards. Here w e show that transferring leaves is another practical method. (C) 2001 Acade mic Press.