The citrus rust mite (CRM), Phyllocoptruta oleivora (Acari: Eriophyidae) is a cosmopolitan key pest of citrus, inflicting severe economic damage if not controlled. In Israel, CRM damages all citrus cultivars. International regulation and increasing control failures of CRM led growers to seek sustainable biological control solutions such as acarine biological control agents. Laboratory studies conducted in Israel have indicated that the indigenous predator species Amblyseius swirskii, Iphiseius degenerans, Typhlodromus athiasae and Euseius scutalis (all Acari: Phytoseiidae) can potentially control CRM. Our general objective in the present study was to bridge the gap of knowledge between laboratory studies and the lack of control efficacy of these species in commercial orchards. Predator augmentation in the field showed that although predator populations increased immediately following releases they later decreased and did not affect CRM populations. When A. swirskii augmentation was combined with a series of maize pollen applications, A. swirskii populations were enhanced substantially and continuously but again CRM populations were not affected. Growth chamber studies with CRM-infested seedlings, with or without a maize pollen supplement, indicated that pollen provisioning led to population increase of E. scutalis and A. swirskii but only E. scutalis significantly lowered CRM populations. Control with E. scutalis was confirmed in the field on CRM infested seedlings with pollen provisioned by adjacent flowering Rhodes grass. While experiments in mature citrus orchard showed that pollen supplement usually increased predator populations they also indicated that other factors such as intraguild interactions and pesticide treatments should be taken into account when devising CRM biological control programs.
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Acknowledgments We extend our gratitude to the growers of (from South to North) Shibolim, Yesodot, Hadera, Gan Shmuel, Beit She’arim and Beit Ha’emek for their cooperation. We thank Jonathan Abrahams, Shmuel Gross and Benny Ronen for their technical support. We would like to thank Bio-Bee, Israel, and especially Shimon Steinberg, Yehoshua Kaminsky and Arnon Alouche for their cooperation, collaboration and for supplying some of the materials and mites needed for this study. We express our gratitude to Dr. Hillary Voet for her statistical guidance. This work was supported by the Israeli Plant Production and Marketing Board and the Chief Scientist of the Israeli Ministry of Agriculture, research projects 864-0045-08 and 131-1093-03. This manuscript is a contribution of the Institute of Plant Protection, Volcani Center, ARO, Israel.
- Amblyseius swirskii
- Euseius scutalis
- Iphiseius degenerans
- Typhlodromus athiasae