The predatory mite Typhlodromus pyri (Acari: Phytoseiidae) causes feeding scars on leaves and fruits of apple

Typhlodromus pyri Scheuten (Acari: Phytoseiidae) is the most important predator of Panonychus ulmi (Koch) (Acari: Tetranychidae) in orchards and vineyards. It was recently found that adult T. pyri females cause microscopic scars on apple leaves. The present laboratory experiments were carried out to confirm the production of scars on apple leaves and to assess if females cause scars on fruits as well. Scar production on apple leaves and/or fruits was investigated under various nutritional conditions: no food, pollen of Scots pine (Pinus sylvsestris L.) only, nymphs of P. ulmi only, and pollen + prey. Both on leaves and fruits, either offered alone or in combination, feeding scars were produced under all nutritional conditions, but mostly in the 'no food' treatment. The predators consumed significantly more P. ulmi nymphs when offered alone than when offered in combination with pollen. T. pyri laid eggs under all nutritional conditions, but mostly in the 'pollen + prey' treatment and least when no food was offered. T. pyri females caused scars on both leaves and fruits when offered simultaneously, but more on leaves than on fruits. The scars were also bigger on leaves than on fruits in all experiments. T. pyri survived and reproduced on plant material in the absence of other food sources. Whether the scars produced on leaves and fruits harm the quality of fruits or the yield of apple cannot be concluded from the present experiments.