1,720,995 research outputs found
Spatio-temporal dynamics of Drosophila suzukii: A landscape perspective
Full text linkLa composizione del paesaggio svolge un ruolo fondamentale nel controllo delle dinamiche degli insetti. Gli habitat naturali e semi-naturali, nonostante siano fonte di importanti servizi ecosistemici, forniscono siti di svernamento ottimali nonché un'ampia gamma di piante ospiti per numerose specie dannose alle colture. In tal modo possono potenzialmente favorire un aumento delle densità di popolazione di queste specie, promuovendo la loro diffusione nel territorio. A questo proposito, il presente lavoro di tesi si propone di approfondire la relazione tra la distribuzione e il danno di una specie invasiva polifaga, Drosophila suzukii, e l'ambiente fisico circostante. D. suzukii è un insetto approdato di recente in Europa, provocando ingenti danni economici su diversi piccoli frutti di interesse commerciale. La gestione di questo carpofago è particolarmente complessa a causa del suo elevato potenziale dispersivo e della sua polifagia. Nei capitoli 2 e 3 si è studiato l'effetto della composizione del paesaggio sulla distribuzione di D. suzukii e sul danno provocato alle coltivazioni. Nel corso della stagione vegetativa, la marcata presenza di habitat semi-naturali ha fortemente influenzato la risposta del carpofago, con conseguente incremento della densità di popolazione. In particolare, i ceraseti situati in zone boschive sono risultati essere i più attaccati dall'insetto. Nel capitolo 4 è stato attuato un monitoraggio a grande scala geografica al fine di determinare le dinamiche temporali e la sincronizzazione dell'attività di D. suzukii lungo gradienti altitudinali in ambiente alpino. A causa dell'elevato potenziale di dispersione, la sincronizzazione dell’attività delle popolazioni dell'insetto è risultata essere estremamente elevata sia a grandi distanze che a quote molto diverse. Nel capitolo 5 è stato svolto un lavoro preliminare di meta-analisi atto a valutare la relazione tra gli insetti dannosi alle colture e la composizione del paesaggio. Coerentemente con quanto ottenuto dai precedenti studi su D. suzukii, si può osservare come un'alta presenza di habitat naturali e semi-naturali nel paesaggio comporti un aumento delle densità di popolazione di queste specie. Considerando i problemi emergenti legati al recente arrivo di D. suzukii ed altre specie invasive in zone temperate, questo lavoro sottolinea la necessità di approfondire lo studio dei potenziali effetti che la composizione paesaggistica può avere sulle dinamiche spazio-temporali delle popolazioni di insetti invasivi
Tillage regime shapes ground beetle distribution and their potential for weed control under drought conditions
No full textXylFeed – Analysing DC-EPG waveform variables for European spittlebugs and sharpshooters
No full textThe software “XylFeed” is designed as MS Excel macro, developed to analyse essential DC-EPG (Direct Current-Electrical Penetration Graph) waveform variables for European xylem sap-feeding insects (spittlebugs and sharpshooters). DC-EPG waveforms must be manually marked in ‘Stylet+a’ (EPG Systems, Wageningen, Netherlands) or comparable software previously to allow a calculation in “XylFeed”. The software enables the analysis of the probing and feeding activities of European xylem sap-feeding insects through a calculation of sequential and non-sequential EPG variables. A detailed description of the software usage is provided in the Supplementary Material of the connected publication, while software output variables are listed and defined within the software.Peer reviewe
Halyomorpha halys (Hemiptera: Pentatomidae) as the major contributor to early olive drop in northern Italy
No full textIn recent years, a new phenomenon of early olive drop is causing production losses in olive groves throughout
northern Italy. To analyze the possible causes, field and laboratory trials were performed to assess the involvement
of fungal pathogens and insect pests in this disease. External and internal symptoms of fungal infections
or insect-feeding activities were researched. Fungi present in healthy and dislodged olives were investigated.
The relationship between olives that fell and Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) infestation
was assessed in a controlled infestation trial, and the effectiveness of an insecticidal strategy in reducing
early olive drop was tested in open field conditions. A comparable number of fungi, mostly endophytes, were
isolated and identified from both healthy and dislodged olives. The damage observed on dislodged olives
was primarily ascribed to pentatomids feeding activity. Six stink bugs species were found in olive canopies,
that is, the invasive H. halys, which was by far the most abundant, and Acrosternum heegeri Fieber, Nezara
viridula (Linnaeus), Palomena prasina (Linnaeus), Piezodorus lituratus (Fabricious), and Rhaphigaster nebulosa
(Poda). Halyomorpha halys caused intense fruit drop in the controlled infestation trial, and its infestation level
significantly correlated with the number of olives that fell. Native stink bugs, present in much lower population
compared to H. halys, could also partially contribute to early drop of olives. Insect proof net significantly
reduced the early olive drop disease, while insecticide applications only partially reduced the stink bugs population
density and, proportionally, early olive drop
assisted comparison of European spittlebugs and sharpshooters feeding behaviour on grapevine
Full text linkXylem-feeding is apparently the only requirement making an insect a competent vector of the bacterium Xylella fastidiosa, an organism responsible for the devastation of the Southern Italian olive forest and nowadays considered one of the most feared threats to agriculture and landscape in Europe, including vineyards. Here, we used the direct current-electrical penetration graph (DC-EPG) technique to compare and describe the feeding behaviour on grapevine of four xylem-feeding species considered candidate vectors of X. fastidiosa widespread in Europe, namely two spittlebugs (the meadow spittlebug Philaenus spumarius and the spittlebug Neophilaenus campestris) and two sharpshooter leafhoppers (the rhododendron leafhopper Graphocephala fennahi and the green leafhopper Cicadella viridis). We created a standard for the analysis of EPG waveforms recorded with a DC-EPG device, describing feeding activities performed by these insects from stylet insertion into the plant to withdrawal. This standard, along with freely available software, has been developed to harmonize the calculation of feeding behavioural parameters in xylem-feeders. The most relevant differences between the two vector taxa were the probing frequency and the dynamics of xylem ingestion. Sharpshooters tended to perform significantly more probes than spittlebugs. In contrast, the latter spent longer times in low-frequency xylem ingestion, characterized by scattered contractions of the cibarial dilator muscle interspersed with periods of pump inactivity. Cicadella viridis was the species displaying the highest frequency of the electrical pattern found to be associated with X. fastidiosa inoculation in spittlebugs (Xe). Feeding behavioural data presented here represent an important step forward for deepening our knowledge of xylem-sap feeding insects' interaction with both the host plants and the bacterium they transmit
High genetic diversity in the Culex pipiens complex from a West Nile Virus epidemic area in Southern Europe
Full text linkBackground
The Culex pipiens complex includes the most widespread mosquito species in the world. Cx. pipiens is the primary vector of the West Nile Virus (WNV) in Europe and North America. Cases of WNV have been recorded in Italy since 1998. In particular, wet areas along the Po River are considered some of the most WNV affected areas in Italy. Here, we analyzed the genetic structure of ten Cx. pipiens populations collected in the last part of the Po River including the Delta area.
Methods
We assessed the genetic variability of two mitochondrial markers, cytochrome oxidase 1 (COI) and 2 (COII), for a total of 1200 bp, and one nuclear marker, a fragment of acetylcholinesterase-2 (ace-2), 502 bp long. The effect of the landscape features was evaluated comparing haplotype and nucleotide diversity with the landscape composition.
Results
The analysis showed a high genetic diversity in both COI and COII gene fragments mainly shared by the populations in the Delta area. The COI-COII network showed that the set of haplotypes found was grouped into three main supported lineages with the higher genetic variability gathered in two of the three lineages. By contrast, ace-2 fragment did not show the same differentiation, displaying alleles grouped in a single clade. Finally, a positive correlation between mitochondrial diversity and natural wetland areas was found.
Conclusions
The high mitochondrial genetic diversity found in Cx. pipiens populations from the Po River Delta contrasts with the low variability of inland populations. The different patterns of genetic diversity found comparing mitochondrial and nuclear markers could be explained by factors such as differences in effective population size between markers, sex biased dispersal or lower fitness of dispersing females. Moreover, the correlation between genetic diversity and wetland areas is consistent with ecosystem stability and lack of insecticide pressure characteristic of this habitat. The mtDNA polymorphism found in the Po River Delta is even more interesting due to possible linkages between the mitochondrial lineages and different biting behaviors of the mosquitoes influencing their vector ability of arboviral infections
DC-EPG raw data on European spittlebugs and sharpshooters feeding behaviour on grapevine
No full textThe Direct Current-Electrical Penetration Graph (DC-EPG) technique was used to compare and describe the feeding behaviour on grapevine of four xylem sap-feeding species considered candidate vectors of X. fastidiosa and widespread in Europe: the meadow spittlebug Philaenus spumarius, the spittlebug Neophilaenus campestris, the rhododendron leafhopper Graphocephala fennahi and the green leafhopper Cicadella viridis. The four species were settled on potted grapevine plants for a period of 6 hours and the feeding activities performed by these insects, from stylet insertion into the plant to withdrawal were recorded by DC-EPG coupled with Stylet+d software. Characteristic waveforms were marked with Stylet+a software and analysed by the macro XylFeed. The raw data of the sequential and non-sequential EPG parameters generated by the XylFeed are reported in this database as part of the connected publication.Peer reviewe
Impairing the development of an olive fly pest by targeting its symbiotic bacteria in egg-infested fruits
Full text linkThe olive fly Bactrocera oleae is an important pest across the world, and its control has traditionally been achieved through synthetic insecticides. Nowadays, there is a growing demand for reducing chemical use due to environmental and human health concerns. The manipulation of symbiotic bacteria inhabiting insect pests has been proposed as a sustainable strategy, allowing insecticide-free management. Here, the possibility of impairing the strict association between the olive fly and its primary symbiont, 'Candidatus Erwinia dacicola', was tested by preventing bacterial infection of the newborn larvae of the pest. Five commercial products with putative antimicrobial activity were used for treating olives infested with eggs. Results showed a significant reduction of the symbiotic bacterial load in larvae derived from olives treated with dodine and a zinc-copper-citric acid biocomplex, as well as a reduction in the pupation rate of the pest. Our findings for the first time provide evidence of the feasibility of impairing the symbiotic association in olive fly through the application of antimicrobial compounds in olive fruit infested with newly laid eggs
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