Effect of pollen provision on life-history parameters of phytoseiid predators under hot and dry environmental conditions

Abstract

Biological control can be severely disrupted under climate change conditions. This is the case of the spider mite Tetranychus urticae in Spanish citrus orchards, where the omnivorous phytoseiid Euseius stipulatus, the most abundant predator in the system, was highly impacted by hot and dry conditions mimicking future warmer summers. Such a situation can often be compensated by the provision of alternative food to support generalist predators. As a first step to studying whether such a technique could be applied in this case, we studied at laboratory conditions whether pollen could mitigate the negative effects of hotter and drier conditions derived of climate change on three phytoseiids with different diet specializations. In addition to E. stipulatus, these predators, which all together, are considered key for the biological control of T. urticae in citrus, are Neoseiulus californicus and Phytoseiulus persimilis. Our results confirm the extremely fine-tuning of T. urticae to hot–dry conditions. They also provide evidence of the poor performance of E. stipulatus, especially in terms of reproduction, compared to the other two phytoseiids at these conditions, even when high-quality pollen was available. Moreover, access to pollen in combination with T. urticae eggs enhanced survival but reduced predation and oviposition relative to a T. urticae-only diet for N. californicus and P. persimilis. Therefore, whether the overall effect of pollen would justify its use in citrus to counteract the deleterious effects of a hotter and drier climate on the natural regulation of T. urticae is still controversial.