Insecticidal potential of Brevibacillus laterosporus against dipteran pest species in a wide ecological range.

In order to increase our understanding of the insecticidal potential of the entomopathogenic bacterium Brevibacillus laterosporus strain UNISS 18 against insect pests, investigations were conducted on a selection of dipteran species including fruit flies, house flies, blow flies, and mosquitoes, characterized by adaptations to very diverse habitats. According to lethal concentration (LC50) values, the common house mosquito Culex pipiens (LC50 = 0.10 × 106 spores/mL) and the yellow fever mosquito Aedes aegypti (LC50 = 0.18 × 106 spores/mL) were significantly more susceptible than the flies. The blow flies were the second taxon in term of susceptibility to B. laterosporus spores, with a higher mortality in Calliphora vomitoria (LC50 = 78.84 × 106 spores/mL) than Lucilia caesar (LC50 = 148.30 × 106 spores/mL). The effectiveness of B. laterosporus spores was reduced by half in the house fly Musca domestica (LC50 = 82.41 × 106 spores/mL). The lowest susceptibility was observed in the fruit flies, among which the spotted wing drosophila (SWD), Drosophila suzukii, was the most susceptible (LC50 = 217.51 × 106 spores/mL) in comparison with the medfly Ceratitis capitata and the olive fly Bactrocera oleae (LC50 = 2567.32 and 2567.36 × 106 spores/mL, respectively). The present study demonstrated that significantly different degrees of susceptibility are associated with diverse dipteran species including plant and animal parasites, and we suggest that B. laterosporus established different relationships with dipteran species in different ecosystems.

The Ha-ROXL gene is required for initiation of axillary and floral meristems in sunflower.

Axillary meristems (AMs) contribute to the growth of a plant, determining adult architecture and reproductive success in response to environmental stimuli. The missing flowers (mf) mutant of sunflower (Helianthus annuus) is defective in AM development. mf lacks shoot branching and ray flowers, occasionally producing few disk flowers. Here we demonstrated that a point mutation in the REGULATOR OF AXILLARY MERISTEM FORMATION-LIKE (Ha-ROXL) gene of mf generates a premature stop codon and therefore a nonfunctional bHLH transcription factor, no longer localized in the nucleus, where it should exert its function. Virus-induced gene silencing of Ha-ROXL also causes defects in disk and ray flower development. Ha-ROXL mRNA accumulates at the adaxial boundaries of leaves and AMs. During inflorescence development, Ha-ROXL is expressed in small arcs of cells before a clear separation between abaxial bracts and disk flower primordia. No Ha-ROXL mRNA accumulates in mf inflorescences. Several genes known to play roles in plant architecture, auxin transport, and flower development are differentially expressed in mf and Ha-ROXL-silenced plants. These results highlight the predominant role of Ha-ROXL in regulating AMs in sunflower. In dicot, mf is the first mutant for which the ROXL gene is also required for initiation of flower meristems.

Leaf and Flower Extracts from the Dwarf Elder (Sambucus ebulus): Toxicity and Repellence against Cosmopolitan Mosquito-Borne Diseases Vectors.

As there has been no scientific evidence of the bioactivity of Sambucus ebulus (Adoxaceae) extracts against insects, we chemically characterized S. ebulus leaves and flowers extracted in methanol and water. The crude extracts, phenolic compounds, and amino acids isolated were tested as larvicides against the fourth-instar larvae of Aedes albopictus and Culex pipiens (Diptera: Culicidae). To understand their mode of action, we evaluated the in vitro acetylcholinesterase (AChE) inhibitor effect of the crude extracts on the two mosquito larvae through a colorimetric method. Furthermore, the deterrent effect of the crude extracts against ovipositing Ae. albopictus females was assessed in the open field. Twelve phenylpropanoids and fourteen amino acids were detected in the extracts, with a prevalence of hydroxycinnamic acids and nonaromatic amino acids. The most toxic compound to Ae. albopictus larvae after 24 h was gallic acid, followed by the crude S. ebulus leaf extract; on Cx. pipiens, it was the crude flower extract. The AChE test showed higher inhibition on both mosquito species exerted by the leaf extract if compared to the flower extract, and it also deterred oviposition by Ae. albopictus females starting from the third day. The results indicated that vegetal extracts could effectively help in the integrated vector management of mosquitoes.

Biological Insights on the Invasive Fig Pest Aclees taiwanensis Kȏno, 1933 (Coleoptera: Curculionidae).

The fig weevil Aclees taiwanensis Kȏno, 1933 (Coleoptera: Curculionidae) is an invasive fig tree pest recently introduced in southern Europe. Reported for the first time in France in 1997 as A. cribratus, and then in Italy in 2005 as A. sp. cf. foveatus, A. taiwanensis is currently threatening fig nurseries, orchards, and wild plants. To date, no control methods have proven to be effective against A. taiwanensis. Although some attempts have been made to describe the insect's biology and behavior, such information is limited to that obtained from adult samples collected in the field. In particular, because of their xylophagous behavior, scarce information is available on the larval stages of the species. The aim of this study, therefore, was to fill these information gaps on the insect biology and behavior by setting up a laboratory protocol suitable for the rearing of A. taiwanensis. Using the developed rearing protocol, we assessed the main fitness parameters of the species including oviposition rate, egg hatchability, embryonic, larval and pupal duration and development, immature survival, pupation behavior, pupal weight, emergence, sex ratio and adult morphological parameters. The proposed rearing procedure allowed us to obtain new information on the main features of the insect's biology that may be useful for setting up strategies for its control.

Essential Oils as Post-Harvest Crop Protectants against the Fruit Fly Drosophila suzukii: Bioactivity and Organoleptic Profile.

The essential oils extracted from mandarin (Citrus reticulata Blanco) fruits, and from tea tree (Maleleuca alternifolia (Maiden and Betche) Cheel) leaves have been chemically analyzed and tested for their bioactivity against D. suzukii. Besides, to estimate consumers' acceptability of the essential oil (EO) treatments, we evaluated their impact on the organoleptic characteristics of the EO-treated fruits. The main chemical constituents of the two EOs were 1,8-cineole and 4-terpineol for M. alternifolia (22.4% and 17.6% of the total components, respectively), and limonene (83.6% of the total components) for C. reticulata. The behavioral tests indicate that the two EOs are able to deter D. suzukii oviposition and that D. suzukii shows positive chemotaxis to low concentrations of the EOs and negative chemotaxis when the EO concentration increases. While no negative effects on the organoleptic profiles were detected for fruits treated with C. reticulata EO, the olfactory profile of fruits treated with M. alternifolia EO was so negative that they were defined as "not suitable for consumption" by panellists. Overall, our findings indicate that the use of EOs for the post-harvest protection of small fruits is feasible, provided that the essential oils are selected not only for their bioactivity against the insect pest but also for their affinity with the consumers' sensorial system.