Effect of pollen quality on the efficacy of two different life-style predatory mites against Tetranychus urticae in citrus

摘要

Cover crops can serve as a reservoir of natural enemies by supplying alternative food sources as pollen.However, pollen quality and availability can modulate phytoseiid communities. In clementine trees associatedwith a cover crop of Festuca arundinacea Schreber, these communities were more diverse thanthose associated with a multifloral wild cover crop. As a consequence, the former had a better regulationof Tetranychus urticae Koch (Acari: Tetranychidae) populations than the latter. Longer provision of higherquality pollen in the multifloral cover relative to F. arundinacea is suspected to interfere with the biologicalcontrol of T. urticae by specific phytoseiid predators (Phytoseiulus persimilis Athias-Henriot and Neoseiuluscalifornicus (McGregor)) by enhancing the less efficient generalist pollen feeder Euseius stipulatus(Athias-Henriot) which is a superior intraguild predator. To determine whether pollen quality is behindthese results, the effect of the provision of two different pollens (Carpobrotus edulis (L.) L. Bolus and F.arundinacea) on the efficacy of two phytoseiid species (E. stipulatus and N. californicus) to regulate T. urticaepopulations has been studied under semi-field conditions. Results suggest that pollen provision doesnot enhance the ability of these phytoseiids to reduce T. urticae populations. However, C. edulis pollenresulted in explosive increases of E. stipulatus numbers that did not occur with F. arundinacea pollen.Therefore, poor quality pollen may prevent pollen feeders from reaching high numbers in the field. Thiseffect could benefit phytoseiid species suffering intraguild predation by E. stipulatus, the predominantphytoseiid species in Spanish citrus orchards and explain field results.