Wild lime psyllid Leuronota fagarae Burckhardt (Hemiptera: Psylloidea) picorna-like virus full genome annotation and classification.

Picorna-like viruses of the order Picornavirales are a poorly defined group of positive-sense, single-stranded RNA viruses that include numerous pathogens known to infect plants, animals, and insects. A new picorna-like viral species was isolated from the wild lime psyllid (WLP), Leuronota fagarae, in the state of Florida, USA, and labelled: Leuronota fagarae picorna-like virus isolate FL (LfPLV-FL). The virus was found to have homology to a picorna-like virus identified in the Asian Citrus Psyllid (ACP), Diaphorina citri, collected in the state of Florida. Computational analysis of RNA extracts from WLP adult heads identified a 10,006-nucleotide sequence encoding a 2,942 amino acid polyprotein with similar functional domain structure to polyproteins of both Dicistroviridae and Iflaviridae. Sequence comparisons of nucleic acid and amino acid translations of the conserved RNA-dependent RNA polymerase, along with the entire N-terminal nonstructural coding region, provided insight into an evolutionary relationship of LfPLV-FL to insect-infecting iflaviruses. Viruses belonging to the family Iflaviridae encode a polyprotein of around 3000 amino acids in length that is processed post-translationally to produce components necessary for replication. The classification of a novel picorna-like virus in L. fagarae, with evolutionary characteristics similar to picorna-like viruses infecting Bactericera cockerelli and D. citri, provides an opportunity to examine virus host specificity, as well as identify critical components of the virus' genome required for successful transmission, infection, and replication. This bioinformatic classification allows for further insight into a novel virus species, and aids in the research of a closely related virus of the invasive psyllid, D. citri, a major pest of Floridian citriculture. The potential use of viral pathogens as expression vectors to manage the spread D. citri is an area that requires additional research; however, it may bring forth an effective control strategy to reduce the transmission of Candidatus Liberibacter asiaticus (CLas), the causative agent of Huanglongbing (HLB).

UV reflective properties of magnesium oxide increase attraction and probing behavior of Asian citrus psyllids (Hemiptera: Liviidae).

Asian citrus psyllid (Diaphorina citri) vectors the bacterium Candidatus Liberibacter asiaticus, the causal pathogen of citrus greening disease that is devastating citrus industries worldwide. Suppressing psyllid populations is crucial to prevent disease spread. An attract-and-kill trap based on psyllid behavior would fill a niche for monitoring and control. To optimize visual attraction of psyllids, the ultraviolet (UV) reflective properties of magnesium oxide (MgO) and/or barium sulfate (BaSO4) were assessed for potential application to a trap surface. Under low UV, high UV and natural sunlight conditions, the reflectance, attraction, and probing behaviors of psyllids were evaluated on surfaces containing magnesium oxide or barium sulfate. Magnesium oxide added to yellow sticky traps enhanced visual response of D. citri. Probing assays demonstrated that magnesium oxide alone or as a mixture with a phagostimulant blend, increased the UV reflectance of substrates, as well as, attraction and probing by psyllids. Results demonstrated that psyllids respond to both short (UV) and long (yellow) wavelengths during orientation, and that these inert compounds can increase UV reflectance and improve attractiveness of an attract-and-kill device.

Size and shape analysis of Trioza erytreae Del Guercio (Hemiptera: Triozidae), vector of citrus huanglongbing disease.

BACKGROUND: The African citrus triozid (ACT) Trioza erytreae Del Guercio (Hemiptera: Triozidae) is one of the most devastating pests of citrus with a well-known role as a vector of the phloem-limited bacteria (Candidatus Liberibacter africanus) associated with huanglongbing (citrus greening disease), currently considered the world's most serious disease of citrus. Although the pest can successfully develop and reproduce on non-citrus host plants, there is no documented information on the geometric morphometry of ACT. We determine the effect of host plants on ACT morphometry under controlled laboratory conditions using traditional and geometric analysis. RESULTS: ACT reared on C. limon and Citroncirus spp. was significantly larger than when reared on the other host plant species. ACT reared on C. anisata and C. tangelo was consistently smaller than that reared on M. koenigii and C. sinensis. Based on warped outline drawings, ACT reared on Citroncirus spp. and Murraya koenigii had narrower wings than when reared on C. anisata, C. limon, and C. sinensis with slightly broader wing patterns. CONCLUSION: This study clearly demonstrates that host plant species affect morphometric variation in ACT, which might have a direct impact on fitness parameters of the pest as well as its potential for dispersion. Wing shape and size appear to be useful in separating populations of ACT into different groups. © 2018 Society of Chemical Industry.

Evidence of behavior-based utilization by the Asian citrus psyllid of a combination of UV and green or yellow wavelengths.

The Asian citrus psyllid, Diaphorina citri, vectors huanglongbing (HLB), the most serious disease affecting citrus globally. D. citri and HLB have spread to the major citrus growing regions of North America causing billions of dollars of damage in Florida alone. The visual behavior of D. citri is not well characterized and more knowledge is needed to improve attractive traps for monitoring and control of the D. citri. Bioassays were conducted to evaluate attraction to light transmitted through different colored filters. The addition of ultra-violet light (< 400 nm) enhanced attraction of D. citri to transparent visual targets made of green or yellow filters. However, attraction to blue targets was unaffected by UV light. This is the first study to demonstrate a phytophagous insect responding to a hue that is a combination of long and short wavelengths. Further testing is needed to determine how D. citri uses such discriminatory powers in the field. Our results further imply that D. citri utilize color vision, as the less intense yellow and green hues were chosen over white light. In summary, this research provides an increased understanding of D. citri visual behavior and can be used for the development of a more attractive D. citri trap than those currently available.

Wavelength and Polarization Affect Phototaxis of the Asian Citrus Psyllid.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a primary pest of citrus due to its status as a vector of the citrus disease, huanglongbing. We evaluated the effects of light of specific wavelength and polarization on phototactic behavior of D. citri using a horizontal bioassay arena. Wavelength-associated positive phototaxis was associated with short wavelength UV (350-405 nm) targets whereas little or no responses were seen in longer wavelength targets in the visible spectrum from green to orange (500-620 nm). Distance walked towards the visual target was greater for UV/blue wavelengths (350-430 nm) than for longer wavelengths. Distances walked towards 365 nm light were greater than to white light, and distances travelled to green, yellow and orange light were similar to those in darkness. A reduced light intensity decreased responses to white and UV (365 nm) light. Polarized light was discriminated and D. citri travelled greater distance in response to white vertically polarized light than to horizontally polarized or unpolarized light of equal intensity. Responses to polarized 405 nm light were greater than to unpolarized light, although without an effect of polarization plane. For 500 nm light, there was no difference between responses to polarized or unpolarized light. There was no effect of age on responses to 405 nm light although 1 day old psyllids travelled faster in the presence of 500 nm green compared to 4-7 day old psyllids. Movement in response to UV and relative stasis in response to longer wavelength light is consistent with observed behaviors of settling on foliage for feeding and dispersing out of the canopy when flush needed for reproduction is scarce.

Effects of Temperature, Photoperiod, and Rainfall on Morphometric Variation of Diaphorina citri (Hemiptera: Liviidae).

Phenotypic plasticity provides a mechanism by which an organism can adapt to new or changing environments. Earlier studies have demonstrated the variability of Diaphorina citri Kuwayama (Asian citrus psyllid) population dynamics, but no analysis of morphological changes induced by seasonal or artificial laboratory-induced conditions has yet been documented. Such morphometric variation has been found to correspond in dispersal capabilities in several insect taxa. In this study, the effects of temperature and photoperiod on morphometric variation of D. citri were examined through laboratory rearing of psyllids under controlled temperatures (20 °C, 28 °C, and 30 °C) and under a short photoperiod of 10.5:13.5 (L:D) h and a long photoperiod of 16:8 (L:D) h. Diaphorina citri were field-collected monthly from three citrus groves in Fort Pierce, Gainesville, and Immokalee, FL, to evaluate potential field-associated environmental effects. Both traditional and geometric morphometric data were used to analyze the correlation between environmental and morphometric variation. A strong correlation was found between temperature and shape change, with larger and broader wings at colder temperatures in the laboratory. Short day length resulted in shorter and narrower wings as well. From the field, temperature, rainfall, and photoperiod were moderately associated with shape parameters. Adult D. citri with blue/green abdomens collected in the laboratory and field studies were larger in size and shape than those with brown/gray abdomens.

Host plant affects morphometric variation of Diaphorina citri (Hemiptera: Liviidae).

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is one of the most serious citrus pests worldwide due to its role as vector of huanglongbing or citrus greening disease. While some optimal plant species for ACP oviposition and development have been identified, little is known of the influence of host plants on ACP size and shape. Our goal was to determine how size and shape of ACP wing and body size varies when development occurs on different host plants in a controlled rearing environment. ACP were reared on six different rutaceous species; Bergera koenigii, Citrus aurantifolia, Citrus macrophylla, Citrus maxima, Citrus taiwanica and Murraya paniculata. Adults were examined for morphometric variation using traditional and geometric analysis based on 12 traits or landmarks. ACP reared on C. taiwanica were consistently smaller than those reared on the other plant species. Wing aspect ratio also differed between C. maxima and C. taiwanica. Significant differences in shape were detected with those reared on M. paniculata having narrower wings than those reared on C. macrophylla. This study provides evidence of wing size and shape differences of ACP based on host plant species which potentially may impact dispersal. Further study is needed to determine if behavioral and physiological differences are associated with the observed phenotypic differences.