Pollen Quality Affects Biological Control of Tetranychus Urticae in Clementine Mandarines

Tetranychus urticae Koch (Acari: Tetranychidae) populations in citrus can be regulated through the management of the cover crop. A mono-specific cover of the grass Festuca arundinacea Schreber (Poaceae) enhanced the diversity and abundance of Phytoseiidae mites compared with a multifloral cover. This increase resulted in a better control of T. urticae. Pollen availability and quality could be behind this result. Whereas multifloral cover offers a long-term source of a wide variety of pollen, F. arundinacea offers one single type of pollen in spring only. As a consequence, the generalist pollen feeder Euseius stipulatus (Athias-Henriot), which is a superior intra-guild predator, is highly favored in multifloral covers. Therefore, poor quality pollen may prevent pollen feeders from reaching high numbers and indirectly benefit T. urticae control by specialist phytoseiids.