Microorganisms from aphid honeydew attract and enhance the efficacy of natural enemies

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their dispersal in natural environment. Here we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which acts as a kairomone enhancing the efficiency of aphid natural enemies. Our findings represent the first case of a host-associated bacterium driving prey location and ovipositional preference for the natural enemy. We show that this bacterium has a key role in tritrophic interactions because it is the direct source of volatiles used to locate prey. Some specific semiochemicals produced by S. sciuri were also identified as significant attractants and ovipositional stimulants. The use of this host-associated bacterium could certainly provide a novel approach to control aphids in field and greenhouse systems

The effect of electron-phonon interaction in iron-doped III-V cubic semiconductors

A theoretical study of optical absorption and emission measurements of Fe2+ as a substitutional impurity in InP and GaP is presented. A new interpretation of the low-temperature absorption spectrum is proposed based on a weak Jahn-Teller interaction between the electronic excited states and a local gap mode of Gamma(5) symmetry. The model also includes the crystal potential, hybridization with the orbitals of the ligands of the host crystal, spin-orbit interaction and a weak dynamic Jahn-Teller coupling of the orbital ground state of Fe2+ with transverse acoustic phonons of Gamma(3) symmetry. The theoretical model describes with good accuracy the measured positions and relative intensities of the spectral lines. In addition, the mass dependence of the local gap mode of Gamma(5) symmetry reproduces the general features of the fine structures associated with the isotopic shifts of the zero-phonon line and the contribution to the isotopic shifts arising from the difference in zero-point energy between the initial and final states of the transition is evaluated

Is the multicolored Asian ladybeetle, Harmonia axyridis, the most abundant natural enemy to aphids in agroecosystems?

The multicolored Asian ladybeetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), was introduced into Western Europe in the late 1990s. Since the late 2000s, this species has been commonly considered one of the most abundant aphid predators in most Western European coun- tries. In spite of the large amount of research on H. axyridis, information concerning its relative abundance in agroecosystems is lacking. This study aims to evaluate the abundance of H. axyridis within the aphidophage community in four crops situated in southern Belgium: wheat, Triticum aestivum L. (Poales: Poaceae), corn, Zea mays, potato, Solanum tuberosum (Solanales: Solanaceae), and broad bean Vicia faba (Fabales: Fabaceae). In order to assess the species diver- sity, the collected data were analyzed by considering (1) the species richness and (2) the evenness according to the Shannon diversity index. Eleven aphidophages were observed in every invento- ried agroecosystem, including five abundant species: three coccinellids, the seven-spotted ladybug, Coccinella septempunctata L. (Coleoptera: Coccinellidae), the 14-spotted Ladybird, Propylea quatuordecimpunctata, and H. axyridis; one hoverfly, the marmalade hoverfly, Episyr- phus balteatus De Geer (Diptera: Syrphidae); and one lacewing, the common green lacewing, Chrysoperla carnea Stephens sensu lato (= s.l.) (Neuroptera: Chrysopidae). Harmonia axyridis has been observed to thrive, breed, and reproduce on the four studied crops. Harmonia axyridis is the most abundant predator of aphids in corn followed by C. septempunctata, which is the main aphid predator observed in the three other inventoried crops. In wheat and potato fields, H. axyridis occurs in low numbers compared to other aphidophage. These observations suggest that H. axyridis could be considered an invasive species of agrosystems, and that potato and wheat may intermittently act as refuges for other aphidophages vulnerable to intraguild predation by this invader. Harmonia axyridis is not the most abundant aphid predator in the main Belgian crops.Impact de la coccinelles asiatique sur l'agriculture wallonn