Release, establishment, and movement of the predator Typhlodromus pyri (Acari: Phytoseiidae) on apple

Abstract In Ontario apple [ Malus × domestica Mill. (Rosaceae)] orchards, the application of certain pesticides kills phytoseiid predatory mites and causes outbreaks of phytophagous mites. We released a strain of the predatory mite Typhlodromus pyri Scheuten (Acari: Phytoseiidae), obtained from Nova Scotia and with organophosphate- and pyrethroid-resistant traits, into adjacent ’McIntosh’ and ’Red Delicious’ apple orchards and followed its progress over four seasons. The T . pyri strain established in the orchards, became the dominant predator, and was associated with low densities of the phytophagous mites Panonychus ulmi Koch and Tetranychus urticae Koch (Acari: Tetranychidae) and Aculus schlechtendali (Nalepa) (Acari: Eriophyidae). It moved slowly through the orchards and took 4 years to reach the 28th tree (84 m) from the release point in both orchards. The predominant wind direction did not appear to influence T . pyri movement. It was present in high numbers on release trees, or trees near these release trees, each summer after release, unlike other predatory species including Typhlodromus caudiglans (Schuster) (Acari: Phytoseiidae), Amblyseius fallacis (Garman) (Acari: Phytoseiidae), and Zetzellia mali (Ewing) (Acari: Stigmaeidae). This species appears particularly useful for biological control of phytophagous mites in Ontario and is worthy of further testing for conservation and augmentative release.