Flies, like all animals, need to find suitable and safe food. Because the principal food source for Drosophila melanogaster is yeast growing on fermenting fruit, flies need to distinguish fruit with ...safe yeast from yeast covered with toxic microbes. We identify a functionally segregated olfactory circuit in flies that is activated exclusively by geosmin. This microbial odorant constitutes an ecologically relevant stimulus that alerts flies to the presence of harmful microbes. Geosmin activates only a single class of sensory neurons expressing the olfactory receptor Or56a. These neurons target the DA2 glomerulus and connect to projection neurons that respond exclusively to geosmin. Activation of DA2 is sufficient and necessary for aversion, overrides input from other olfactory pathways, and inhibits positive chemotaxis, oviposition, and feeding. The geosmin detection system is a conserved feature in the genus Drosophila that provides flies with a sensitive, specific means of identifying unsuitable feeding and breeding sites.
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► Geosmin, the odor of mold, activates only olfactory sensory neurons expressing Or56a ► These neurons connect to projection neurons that respond exclusively to geosmin ► This circuit confers innate avoidance and, upon activation, overrides attraction ► This pathway is used by flies to detect harmful microbes that produce geosmin
A neuronal circuit that detects a volatile chemical released by toxic mold has been mapped in fly brain. Activation of this evolutionarily conserved circuit overrides a number of innate behaviors such as attraction to other odors and egg laying on substrates, revealing the underlying mechanisms of hard-wired and selectively advantageous avoidance of harmful bacteria in the environment.
Insects exhibit complex symbiotic interactions with microorganisms, which provide an opportunity for developing novel pest management strategies. Closely related to
Drosophila melanogaster,
which is ...commonly used as a model to explore insect–microbe interactions,
Drosophila suzukii
is an important invasive insect pest of fruit crops in the Americas and Europe. We provide an overview of
Drosophila
–microbe interactions and review current research with
D. suzukii
. Recent studies revealed yeast and bacterial species associated with
D. suzukii
flies, fly guts and infested fruit. The ecological importance of these insect–microbe interactions is under investigation. Microbes have a strong impact on insect physiology and
D. suzukii
responds both positively and aversively to microbial volatiles. We highlight potential pest management strategies that take advantage of
D. suzukii
–microbe ecology, including improved monitoring as well as management using behavioural manipulation, phagostimulants and biotechnology.
Although the vinegar fly Drosophila melanogaster is arguably the most studied organism on the planet, fundamental aspects of this species’ natural ecology have remained enigmatic 1. We have here ...investigated a wild population of D. melanogaster from a mopane forest in Zimbabwe. We find that these flies are closely associated with marula fruit (Sclerocarya birrea) and propose that this seasonally abundant and predominantly Southern African fruit is a key ancestral host of D. melanogaster. Moreover, when fruiting, marula is nearly exclusively used by D. melanogaster, suggesting that these forest-dwelling D. melanogaster are seasonal specialists, in a similar manner to, e.g., Drosophila erecta on screw pine cones 2. We further demonstrate that the main chemicals released by marula activate odorant receptors that mediate species-specific host choice (Or22a) 3, 4 and oviposition site selection (Or19a) 5. The Or22a-expressing neurons—ab3A—respond strongly to the marula ester ethyl isovalerate, a volatile rarely encountered in high amounts in other fruit. We also show that Or22a differs among African populations sampled from a wide range of habitats, in line with a function associated with host fruit usage. Flies from Southern Africa, most of which carry a distinct allele at the Or22a/Or22b locus, have ab3A neurons that are more sensitive to ethyl isovalerate than, e.g., European flies. Finally, we discuss the possibility that marula, which is also a culturally and nutritionally important resource to humans, may have helped the transition to commensalism in D. melanogaster.
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•Wild African D. melanogaster are seasonally associated with marula fruit•Marula is the likely ancestral host of D. melanogaster•Marula odor activates a key odorant receptor that shows signs of regional adaptation•Marula use may have driven the switch to human commensalism
The origin and biology of wild Drosophila melanogaster have remained enigmatic. Mansourian et al. report here wild flies from a mopane forest in Zimbabwe and show that these flies are seasonally associated with marula. Marula is an important human resource and may have facilitated human commensalism in D. melanogaster.
Bovine viral diarrhea virus (BVDV) is a globally-distributed agent responsible for numerous clinical syndromes that lead to major economic losses. Two species, BVDV-1 and BVDV-2, discriminated on the ...basis of genetic and antigenic differences, are classified in the genus
within the
family and distributed on all of the continents. BVDV-1 can be segregated into at least twenty-one subgenotypes (1a-1u), while four subgenotypes have been described for BVDV-2 (2a-2d). With respect to published sequences, the number of virus isolates described for BVDV-1 (88.2%) is considerably higher than for BVDV-2 (11.8%). The most frequently-reported BVDV-1 subgenotype are 1b, followed by 1a and 1c. The highest number of various BVDV subgenotypes has been documented in European countries, indicating greater genetic diversity of the virus on this continent. Current segregation of BVDV field isolates and the designation of subgenotypes are not harmonized. While the species BVDV-1 and BVDV-2 can be clearly differentiated independently from the portion of the genome being compared, analysis of different genomic regions can result in inconsistent assignment of some BVDV isolates to defined subgenotypes. To avoid non-conformities the authors recommend the development of a harmonized system for subdivision of BVDV isolates into defined subgenotypes.
Biological control
, or
biocontrol
, is the exploitation of living agents (incl. viruses) to combat pestilential organisms (incl. pathogens, pests, and weeds) for diverse purposes to provide human ...benefits. Thus, during the last century the practices and concepts involved have evolved in separate streams associated with distinct scientific and taxonomic disciplines. In parallel developments, there have been increasing references to biological control in industrial contexts and legislation, resulting in conceptual and terminological disintegration. The aim of this paper is to provide a global conceptual and terminological platform that facilitates future development of the field. We review use of previously suggested terms in key fields (e.g., phytopathology, entomology, and weed science), eliminate redundant terminology, identify three principles that should underpin the concept, and then present a new framework for biological control, rooted in seminal publications. The three principles establish that (1) only living agents can mediate biological control, (2) biological control always targets a pest, directly or indirectly, and (3) all biocontrol methods can be classified in four main categories depending on whether resident agents are utilized, with or without targeted human intervention (
conservation biological control
and
natural biological control
, respectively) or agents are added for permanent or temporary establishment (
classical biological control
and
augmentative biological control
, respectively). Correct identification of what is, and is not, biological control can help efforts to understand and optimize biological pest control for human and environmental benefits. The new conceptual framework may contribute to more uniform and appropriate regulatory approaches to biological control, and more efficient authorization and application of biocontrol products.
Biological control has developed into a realistic alternative to replace chemical pesticides. A long-awaited paradigm shift is now adopted by the European Commission through a proposed new Regulation ...on sustainable use of plant protection products. Unfortunately, the scientific framework underpinning biocontrol is seriously neglected, impeding transition to sustainable plant production.
1. The highly invasive spotted wing Drosophila Drosophila suzukii is a key pest of soft fruit and berries in Europe and North America, and development of control techniques is an urgent research ...challenge. Drosophila suzukii is widely associated with the yeast Hanseniaspora uvarum. Yeasts are symbionts of drosophilid flies and communicate with insects through volatile metabolites for spore dispersal. Accordingly, yeasts and behaviour-modifying chemicals produced by yeasts are prospective tools for environmentally sound insect management. 2. We first bioassayed flight attraction, feeding and oviposition of D. suzukii females in response to H. uvarum yeast and blueberries, which are a preferred host fruit. We then investigated the combined effect of yeast and insecticide on adult female oviposition behaviour and mortality towards the development of a yeast-based control method. 3. Following mating, attraction of female flies to blueberry and yeast odour cues was strongly enhanced. Yeast feeding significantly increased in mated females, while yeast did not increase oviposition on blueberries. This observation suggests that mated flies become attracted to yeast for feeding and to fruit for egg laying. A combined feeding-oviposition assay demonstrated different roles and interference between yeast and fruit stimuli: during the day after mating, females laid fewer eggs when yeast was available. 4. The post-mating yeast-feeding response is an opportunity for the development of an attract-and-kill technique for population control of D. suzukii. Exposing flies to a blend of yeast and insecticide reduced oviposition and greatly enhanced adult fly mortality compared with an insecticide treatment alone. 5. Synthesis and applications. Mated females are the key life stage for Drosophila suzukii population control. Egg-laying females perforate fruit skin and fungal infestations ensue, even when eggs and larvae are killed off by insecticide sprays. Behaviour-modifying chemicals, including yeast metabolites, enable environmentally safe insect management via manipulation of olfactory-mediated reproductive behaviour. Our results highlight that yeast and yeast semiochemicals hold potential for D. suzukii management and that response modulation to olfactory stimuli following mating is a vital element for the development of D. suzukii control methods. Yeast feeding is enhanced in mated D. suzukii females, and this change in post-mating behaviour can be exploited by an attract-and-kill strategy, combining a fly-associated yeast with an insecticide. Furthermore, using the D. suzukii yeast mutualist, H. uvarum, may reduce non-target effects and increase species specificity, which further contributes to the development of an efficient and safe control method.
Predatory long-legged flies of the genus
Medetera
are important, but currently understudied, natural enemies of Scolytinae bark beetles such as
Ips typographus
.
Medetera
flies lay eggs on ...beetle-infested trees, where the developing larvae find their prey, but the chemical cues used by
Medetera
to locate infested trees are currently unknown. To identify odors attracting
Medetera signaticornis,
a species in Europe, headspace samples were collected at several time-points through different stages of
I. typographus
attacks on logs of Norway spruce (
Picea abies
). The headspace samples were analyzed using combined gas chromatography and mass spectrometry (GC–MS), and gas chromatography coupled with electroantennographic detection (GC-EAD) to determine compounds that stimulate
M. signaticornis
antennae. Antennae of
M. signaticornis
males and females were found to detect (–)-
cis
-verbenol, ( +)-
trans
-verbenol and myrtenol, which are known to be produced by bark beetles. Antennal responses were also observed for verbenene, isoterpinolene, α-pinene oxide, camphor, pinocamphone, terpinene-4-ol, myrtenal, borneol, α-terpineol, geranyl acetone, and verbenone, which are primarily produced by microorganisms, and α-pinene, α-fenchene, β-pinene, camphene, 3-carene, limonene, γ-terpinene, and terpinolene, known spruce tree compounds. In field experiments testing two synthetic blends containing 18 antennal active and two additional compounds 2-methyl-3-buten-2-ol and ipsdienol we observed significant attraction of
M. signaticornis
within 24 h. These attractive blends can form the basis for development of
Medetera
monitoring lures for use in future forest and pest management.
The Flaviviridae is a family of small enveloped viruses with RNA genomes of 9000-13 000 bases. Most infect mammals and birds. Many flaviviruses are host-specific and pathogenic, such as hepatitis C ...virus in the genus Hepacivirus. The majority of known members in the genus Flavivirus are arthropod borne, and many are important human and veterinary pathogens (e.g. yellow fever virus, dengue virus). This is a summary of the current International Committee on Taxonomy of Viruses (ICTV) report on the taxonomy of the Flaviviridae, which is available at www.ictv.global/report/flaviviridae.
Sexual Behavior of Drosophila suzukii Revadi, Santosh; Lebreton, Sébastien; Witzgall, Peter ...
Insects,
03/2015, Volume:
6, Issue:
1
Journal Article
Peer reviewed
Open access
A high reproductive potential is one reason for the rapid spread of Drosophila suzukii in Europe and in the United States. In order to identify mechanisms that mediate mating and reproduction in D. ...suzukii we studied the fly's reproductive behavior, diurnal mating activity and sexual maturation. Furthermore, we studied the change of female cuticular hydrocarbons (CHCs) with age and conducted a preliminary investigation on the role of female-derived chemical signals in male mating behavior. Sexual behavior in D. suzukii is characterized by distinct elements of male courtship leading to female acceptance for mating. Time of day and age modulate D. suzukii mating activity. As with other drosophilids, female sexual maturity is paralleled by a quantitative increase in CHCs. Neither female CHCs nor other olfactory signals were required to induce male courtship, however, presence of those signals significantly increased male sexual behavior. With this pilot study we hope to stimulate research on the reproductive biology of D. suzukii, which is relevant for the development of pest management tools.
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