Microorganisms from aphids attract hoverflies and enhance their efficacy

Aphids are some of the most serious pests of crops worldwide, causing major yield and economic losses. They damage plants by feeding on the phloem sap, excreting copious amounts of honeydew and, in some cases, vectoring plant diseases. Here, we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which is involved in the release of semiochemicals acting as a kairomone for aphid natural enemies. These semiochemicals were identified by Solid-Phase Microextraction (SPME) and Gas Chromatography-Mass Spectrometry (GC-MS). Our results show that this bacterium plays a key role in the interactions between aphids and natural enemies because it is the direct source of volatiles used by the aphidophagous hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae) to locate its aphid prey. Through wind-tunnel experiments, some specific semiochemicals produced by S. sciuri were identified as significant attractants and ovipositional stimulants. Also, assays under greenhouses and in potato fields have demonstrated that a culture medium containing the bacterium S. sciuri strongly attracts and induces the oviposition of hoverflies, enhancing their efficiency as biological control agents. The use of this no pathogenic bacterium could provide a very novel approach towards enhancing the efficacy of biological control agents to control aphids in field crops and greenhouse systems.