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Mites to save Valencian orange exports
19 November 2012
A study coordinated by researchers from the Universitat Politècnica de València, in collaboration with the University of Navarra and the Belgian company Biobest Belgium NV has found that soil-dwelling predatory mites are a perfect partner to address the plague of thrips in citrus caused by Pezothrips kellyanus, a tiny insect that affects the skin of the fruit. His work has been published recently in the journal ‘Biological Control’.
Valencia professor Ferran García explains that thrips are a serious economic problem for the citrus sector: "This bug causes a round scar on the top of fruit. This is a purely aesthetic condition, but with serious consequences. For example, half of the Valencian production is exported and a fruit affected by this pest can not be exported, with the economic losses it entails."
To try to find a solution to this problem, researchers began to study for the first time the fauna in the orchard soil and its effect on the pest. "This is the first study in Spain that has evaluated the behaviour of soil mites and how their presence can affect the thrips population and, therefore, the presence or absence of damage to the crop," says the researcher Cristina Navarro.
The Universitat Politècnica de València experts analyzed four citrus orchards located in Valencia and identified fifteen species of eight families of mites, the most abundant were Parasitus americanus (Parasitidae) and Gaeolaelaps aculeifer (Hypoaspis aculeifer). From the results of field and laboratory tests, the mite that best could act against the plague is Gaeolaelaps aculeifer. "The study concluded that there is a direct relationship between a high presence of this mite in the earth and a low presence of thrips on the fruit. This suggests that these mites could be an alternative to the chemical products currently used," says Ferran García.
The more manure, less trips
The researchers also conducted several tests to determine if foliar applications of insecticides or the addition of organic matter to the soil affects the abundance of soil-dwelling predatory mites. "Those lands to which manure composting is added have more predatory mites, while a treatment with the insecticide chlorpyrifos does not affect their number," adds Cristina Navarro.