Soil-dwelling predatory mites in citrus: Their potential as natural enemies of thrips with special reference to Pezothrips kellyanus (Thysanoptera: Thripidae)

Abstract

Free-living predatory mites (Acari) is one of the most abundant and species-rich group of arthropods in the soil, with a great potential for pest control. In the present study we examined the predatory mite fauna in the soil of citrus orchards in order to evaluate their potential as natural enemies of thrips pests and especially of Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae). Moreover, two trials were conducted to assess if foliar sprays of the insecticide chlorpyrifos or the addition of organic compost to the soil affect the abundance of soil predatory mites. Samples of soil were regularly taken from four citrus orchards in Valencia (Spain) from December 2008 to April 2010. Thrips and predatory mites were extracted with Berlese funnels. The thrips fauna in the soil was dominated by P. kellyanus, which accounted for 80% of the specimens registered. With respect to predatory mites, 15 species from eight families were identified. The most abundants were Parasitus americanus (Parasitidae), Hypoaspis (Gaeolaelaps) aculeifer, Hypoaspis (Gaeolaelaps) praesternalis and Hypoaspis sp. (Laelapidae), Neomolgus sp. (Bdellidae), Pachylaelaps islandicus (Pachylaelapidae), Neogamasus sp. (Parasitidae) and Macrocheles scutatiformis (Macrochelidae). Higher populations of H. aculeifer were associated with lower abundance and fruit damage caused by P. kellyanus. Treatment with Chlorpyriphos did not affect the abundance of soil predatory mites and significantly more mites were found in the experimental plots where organic compost was added.