The interaction between insects and gut bacterial symbionts is, nowadays, regarded as an important element in the implementation of pest management, in consideration of the urgent need for ...sustainable alternatives to insecticide use. In this framework, a major tool is symbiotic control, with the main ready-to-use application represented by the interruption of obligate symbioses. Two insect families, namely Pentatomidae in the Hemiptera order and Tephritidae in Diptera, have been indicated as outstanding targets for symbiont-oriented control tactics. An important advantage of interrupting obligate symbioses is the target shift from insect to bacteria, which avoids insecticide use; however, the compatibility between this approach and other pest/disease management strategies is crucial to design low-impact pest control programs. Here we present the state of knowledge regarding the integration of symbiont manipulation in sustainable plant protection plans. Research assessing the potential for multitarget applications is reported, as well as studies on the impact of symbiont interruption on nontarget species. Besides symbiont-targeted pest control, another relevant outcome of symbiont manipulation is the restoration of microbial perturbation in mass-reared insects used in pest control programs, which is a required step to allow the success of other tactics, such as the Sterile Insect Technique. Despite the potential contribution that symbiont-targeted strategies may offer to integrated pest management, we point out that operational caveats may emerge in symbiont-oriented control in relation to the target extension on the label directions and to the number of required treatments. Future work is needed to increase the target range and the number of tested formulations exploiting the interruption of bacterial symbioses. This will also require assessment of the effect of different products on beneficial organisms, including biological control agents. Finally, the authorization of formulates for symbiotic control should be taken into consideration by the regulatory bodies, to really promote new readily available control options.
Some pathogenic phloem‐limited bacteria are a major threat for worldwide agriculture due to the heavy economic losses caused to many high‐value crops. These disease agents – phytoplasmas, ...spiroplasmas, liberibacters, and Arsenophonus‐like bacteria – are transmitted from plant to plant by phloem‐feeding Hemiptera vectors. The associations established among pathogens and vectors result in a complex network of interactions involving also the whole microbial community harboured by the insect host. Interactions among bacteria may be beneficial, competitive, or detrimental for the involved microorganisms, and can dramatically affect the insect vector competence and consequently the spread of diseases. Interference is observed among pathogen strains competing to invade the same vector specimen, causing selective acquisition or transmission. Insect bacterial endosymbionts are another pivotal element of interactions between vectors and phytopathogens, because of their central role in insect life cycles. Some symbionts, either obligate or facultative, were shown to have antagonistic effects on the colonization by plant pathogens, by producing antimicrobial substances, by stimulating the production of antimicrobial substances by insects, or by competing for host infection. In other cases, the mutual exclusion between symbiont and pathogen suggests a possible detrimental influence on phytopathogens displayed by symbiotic bacteria; conversely, examples of microbes enhancing pathogen load are available as well. Whether and how bacterial exchanges occurring in vectors affect the relationship between insects, plants, and phytopathogens is still unresolved, leaving room for many open questions concerning the significance of particular traits of these multitrophic interactions. Such complex interplays may have a serious impact on pathogen spread and control, potentially driving new strategies for the containment of important diseases.
Phloem‐limited bacterial phytopathogens, transmitted among plants by phloem‐feeding Hemiptera vectors, cause heavy losses in agriculture. Associations of pathogens and vectors form complex networks of interactions involving also the microbial community harboured by the insect host; bacterial interactions may have beneficial or detrimental influences on a vector's efficacy. How such complex interplays affect insect‐plant‐bacteria interactions is still unresolved; however, their impact on pathogen spread and control could drive new strategies for the containment of important diseases.
Orientus ishidae (Matsumura) (subfamily Deltocephalinae) is an Asian species now widespread in Europe, and a vector of 16SrV phytoplasmas agents of grapevine Flavescence dorée (FDP). Embryonic and ...post-embryonic development, spatial distribution, and relationships with grapevine of nymphs were studied under field and laboratory conditions. Egg-hatching dynamics and post-embryonic development of nymphs were studied by collecting grapevine wood from managed and unmanaged vineyards (including bot European Vitis vinifera L., and wild American rootstocks) and storing it inside rearing cages at T = 21–23°C. Field sampling of nymphs were made on both grapevine and two elective host plants of O. ishidae: hazelnut and hornbeam. Taylor's Power Law was applied to assess the aggregation coefficient of early- (first and second) and late- (third to fifth) life instars on leaves and shoots of host plants. More nymphs were obtained from wood collected in unmanaged rather than managed vineyards. Under lab conditions, the embryonic development lasted 34–48 d, whereas the whole post-embryonic development averaged 27 d. Under field conditions, early instars peaked at the end of May, and late instars peaked 2–4 wk later. The aggregation patterns decreased from early to late instars, and from leaves to shoots. Very few nymphs were observed on unmanaged grapevine, either European or American, and none on managed European grapevine. Some behavioral and FDP epidemiological consequences of the results obtained are discussed.
Summary
Popillia japonica Newman (Coleoptera: Scarabaeidae) is a highly polyphagous invasive beetle originating from Japan. This insect is highly resilient and able to rapidly adapt to new ...vegetation. Insect‐associated microorganisms can play important roles in insect physiology, helping their hosts to adapt to changing conditions and potentially contributing to an insect's invasive potential. Such symbiotic bacteria can be part of a core microbiota that is stably transmitted throughout the host's life cycle or selectively recruited from the environment at each developmental stage. The aim of this study was to investigate the origin, stability and turnover of the bacterial communities associated with an invasive population of P. japonica from Italy. Our results demonstrate that soil microbes represent an important source of gut bacteria for P. japonica larvae, but as the insect develops, its gut microbiota richness and diversity decreased substantially, paralleled by changes in community composition. Notably, only 16.75% of the soil bacteria present in larvae are maintained until the adult stage. We further identified the micro‐environments of different gut sections as an important factor shaping microbiota composition in this species, likely due to differences in pH, oxygen availability and redox potential. In addition, P. japonica also harboured a stable bacterial community across all developmental stages, consisting of taxa well known for the degradation of plant material, namely the families Ruminococcacae, Christensenellaceae and Lachnospiraceae. Interestingly, the family Christensenallaceae had so far been observed exclusively in humans. However, the Christensenellaceae operational taxonomic units found in P. japonica belong to different taxonomic clades within this family.
The vibrational communication and mating behaviour of the graminicolous leafhoppers
,
,
,
,
, and
were investigated to explain why the first five species hybridize.
was used as a control species. All ...species behaved in the same way and no significant statistical differences were detected with regard to male calls, while female calls and the male courtship song differed in
, thus showing that a specific pre-mating isolation mechanism was used by the latter species and the first five ones lacked such a mechanism. In addition,
is missing in Italy, while the other species live allopatrically in Italy, with the only exceptions being
and
, which live in Sicily and are often found in sympatry, and
and
, which live in Sardinia. All these species can be distinguished by means of male genital appendages; however,
is longer and has a different body colour. The existence of natural hybrids of
,
, and
in the Italian peninsula and their hybridization in the laboratory with
and
require the investigation of possible post-mating reproductive barriers before re-considering their systematic validity.
This paper reviews the existing predictive models concerning insects and mites harmful to grapevine. A brief conceptual description is given on the definition of a model and about different types of ...models: deterministic vs. stochastics, continuous vs. discrete, analytical vs. computer-based, and descriptive vs. data-driven. The main biological aspects of grapevine pests covered by different types of models are phenology, population growth and dynamics, species distribution, and invasion risk. A particular emphasis is put on forecasting epidemics of plant disease agents transmitted by insects with sucking-piercing mouthparts. The most investigated species or groups are the glassy-winged sharpshooter
(Germar) and other vectors of
subsp.
, a bacterium agent of Pierce's disease; the European grape berry moth,
(Denis and Schiffermuller); and the leafhopper
Ball, the main vector of phytoplasmas agents of Flavescence dorée. Finally, the present and future of decision-support systems (DSS) in viticulture is discussed.
During oviposition, ectoparasitoid wasps not only inject their eggs but also a complex mixture of proteins and peptides (venom) in order to regulate the host physiology to benefit their progeny. ...Although several endoparasitoid venom proteins have been identified, little is known about the components of ectoparasitoid venom. To characterize the protein composition of Torymus sinensis Kamijo (Hymenoptera: Torymidae) venom, we used an integrated transcriptomic and proteomic approach and identified 143 venom proteins. Moreover, focusing on venom gland transcriptome, we selected additional 52 transcripts encoding putative venom proteins. As in other parasitoid venoms, hydrolases, including proteases, phosphatases, esterases, and nucleases, constitute the most abundant families in T. sinensis venom, followed by protease inhibitors. These proteins are potentially involved in the complex parasitic syndrome, with different effects on the immune system, physiological processes and development of the host, and contribute to provide nutrients to the parasitoid progeny. Although additional in vivo studies are needed, initial findings offer important information about venom factors and their putative host effects, which are essential to ensure the success of parasitism.
Rhynchophorus ferrugineus, also known as the red palm weevil, is regarded as the major pest of palm trees. Although studies of the microbiota associated with this species have been performed in ...recent years, little attention has been dedicated to the influence of the diet in shaping the host bacterial community. Here, we investigated the influence of food sources (i.e. palm tissues vs apple based substrate) on the microbial diversity associated with RPW, which was compared with the microbiota associated with wild individuals of the sister species Rhynchophorus vulneratus. The bacterial characterization was performed using a culture independent approach, i.e. the 16S rRNA pyrotag, and a culture dependent approach for a subset of the samples, in order to obtain bacterial isolates from RPW tissues. The bacterial community appeared significantly influenced by diet. Proteobacteria resulted to be the most abundant clade and was present in all the specimens of the three examined weevil groups. Within Proteobacteria, Enterobacteriaceae were identified in all the organs analysed, including hemolymph and reproductive organs. The apple-fed RPWs and the wild R. vulneratus showed a second dominant taxon within Firmicutes that was scarcely present in the microbiota associated with palm-fed RPWs. A comparative analysis on the bacteria associated with the palm tissues highlighted that 12 bacterial genera out of the 13 identified in the plant tissues were also present in weevils, thus indicating that palm tissues may present a source for bacterial acquisition.
The core gut microbiome of adult honeybee comprises a set of recurring bacterial phylotypes, accompanied by lineage-specific, variable, and less abundant environmental bacterial phylotypes. Several ...mutual interactions and functional services to the host, including the support provided for growth, hormonal signaling, and behavior, are attributed to the core and lineage-specific taxa. By contrast, the diversity and distribution of the minor environmental phylotypes and fungal members in the gut remain overlooked. In the present study, we hypothesized that the microbial components of forager honeybees (i.e., core bacteria, minor environmental phylotypes, and fungal members) are compartmentalized along the gut portions. The diversity and distribution of such three microbial components were investigated in the context of the physico-chemical conditions of different gut compartments. We observed that changes in the distribution and abundance of microbial components in the gut are consistently compartment-specific for all the three microbial components, indicating that the ecological and physiological interactions among the host and microbiome vary with changing physico-chemical and metabolic conditions of the gut.
The biocontrol agent
Torymus sinensis
has been released into Japan, the USA, and Europe to suppress the Asian chestnut gall wasp,
Dryocosmus kuriphilus
. In this study, we provide a quantitative ...assessment of
T. sinensis
effectiveness for suppressing gall wasp infestations in Northwest Italy by annually evaluating the percentage of chestnuts infested by
D. kuriphilus
(infestation rate) and the number of
T. sinensis
adults that emerged per 100 galls (emergence index) over a 9-year period. We recorded the number of
T. sinensis
adults emerging from a total of 64,000 galls collected from 23 sampling sites. We found that
T. sinensis
strongly reduced the
D. kuriphilus
population, as demonstrated by reduced galls and an increased
T. sinensis
emergence index. Specifically, in Northwest Italy, the infestation rate was nearly zero 9 years after release of the parasitoid with no evidence of resurgence in infestation levels. In 2012, the number of
T. sinensis
females emerging per 100 galls was approximately 20 times higher than in 2009. Overall,
T. sinensis
proved to be an outstanding biocontrol agent, and its success highlights how the classical biological control approach may represent a cost-effective tool for managing an exotic invasive pest.
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