Seasonal activity of Trechnites insidiosus (Hymenoptera: Encyrtidae) and its host Cacopsylla pyricola (Hemiptera: Psyllidae) in pear.

Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae) is the most expensive and challenging insect pest of commercial pear trees in the Pacific Northwest. Integrated pest management (IPM) programs are working toward relying more heavily on natural enemies to reduce insecticide use. Trechnites insidiosus (Crawford) (Hymenoptera: Encyrtidae) is the main parasitoid of C. pyricola, but little is known about its biology in the region. Developing sampling tools is important for the deployment of IPM programs, including monitoring of natural enemies. In this study, we examined 2 conventional monitoring methods: beat trays and yellow sticky cards, in addition to screened sticky cards and 3D-printed cylinder traps. Additionally, we tested an overwintering trap for the collection of parasitized C. pyricola. The trapping methods were tested in orchards in Oregon and Washington. Unscreened cards caught the most T. insidiosus and C. pyricola, followed by screened cards, cylinder traps, and then beat trays. Beat trays sometimes failed to catch any T. insidiosus, even when it was found in abundance via other methods. Screened cards and cylinder traps reduced bycatch and increased ease of identifying T. insidiosus. Specimens from the cylinder traps were also more suitable for use in molecular analysis. The overwintering traps were effective at capturing parasitized C. pyricola, but were highly variable year to year. The ideal trapping method will vary based on research needs (e.g., DNA preservation, reducing bycatch, catching higher numbers), but both screened sticky cards and cylinder traps were viable methods for monitoring T. insidiosus and its host.

A new Australian species of invasive psyllid, Acizzia convector Burckhardt & Taylor, sp. nov. (Psylloidea: Psyllidae) associated with Acacia auriculiformis and A. mangium (Fabaceae).

Acizzia convector Burckhardt & Taylor, sp. nov., a psyllid originating from Australia, is described from material from Australia (NT), South and Southeast Asia (Brunei, Cambodia, India, Laos, Malaysia [Sabah], Singapore and Thailand) and North America (USA [Florida from six counties]). The new species is diagnosed and illustrated, and a key is provided to identify the adults of Acizzia species adventive in the New World. The new species develops on Acacia auriculiformis and A. mangium (Fabaceae), two mimosoids planted and widely naturalised throughout the tropics. While the presence of A. convector sp. nov. in Florida is probably recent (earliest record from October 2014), it occurs in Southeast Asia at least since the 1980s. The wide distribution of the host plants in tropical Africa and South America would allow the psyllids also to occur there.

Association of Two Bactericera Species (Hemiptera: Triozidae) With Native Lycium spp. (Solanales: Solanaceae) in the Potato Growing Regions of the Rio Grande Valley of Texas.

Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is a vector of 'Candidatus Liberibacter solanacearum' (Lso), the pathogen that causes potato zebra chip. Zebra chip incidence varies regionally, perhaps because of geographic differences in species of noncrop hosts available to the vector and in susceptibility of those hosts to Lso. Native and introduced species of Lycium (Solanales: Solanaceae) are important noncrop hosts of B. cockerelli in some regions of North America. Susceptibility of native Lycium species to Lso is uncertain. We investigated the use of two native species of Lycium by B. cockerelli in South Texas and tested whether they are susceptible to Lso. Bactericera cockerelli adults and nymphs were collected frequently from L. berlandieri Dunal and L. carolinianum Walter. Greenhouse assays confirmed that B. cockerelli develops on both species and showed that Lso infects L. carolinianum. Molecular gut content analysis provided evidence that B. cockerelli adults disperse between potato and Lycium. These results demonstrate that L. berlandieri and L. carolinianum are likely noncrop sources of potato-colonizing B. cockerelli in South Texas and that L. carolinianum is a potential source of Lso-infected psyllids. We also routinely collected the congeneric psyllid, Bactericera dorsalis (Crawford), from both Lycium species. These records are the first for this psyllid in Texas. Bactericera dorsalis completed development on both native Lycium species, albeit with high rates of mortality on L. berlandieri. B. dorsalis acquired and transmitted Lso on L. carolinianum under greenhouse conditions but did not transmit Lso to potato. These results document a previously unknown vector of Lso.

An annotated and illustrated catalog of the primary type material of Hemiptera deposited in the Florida State Collection of Arthropods.

The Florida State Collection of Arthropods (FSCA) is one of the largest and most diverse insect collections in North America and the largest in the southeastern United States with over twelve million curated specimens and significant amounts of materials in bulk collections and other unprocessed samples. The order Hemiptera currently comprises approximately 95,000 species in three suborders. The FSCA houses type material in the auchenorrhynchan families Cicadidae, Cicadellidae, Cixiidae, Delphacidae, Derbidae, and Membracidae; the heteropteran families Coreidae, Corixidae, Curaliidae, Lygaeidae, Miridae, Pentatomidae, Reduviidae, Schizopteridae, Scutelleridae, and Tingidae; the sternorrhynchan families Aleyrodidae, Aphalaridae, Aphididae, Coccidae, Diaspididae, Matsucoccidae, Pseudococcidae, Phacopteronidae, and Triozidae. This catalog documents the FSCA primary type material for 167 species in 79 genera in 24 families across the three suborders.

Balclutha jafara (Hemiptera: Cicadellidae): integrative identification of a species introduced in the Western Hemisphere, and notes on other Balclutha.

Leafhopper specimens of the genus Balclutha Kirkaldy, found in southern Florida (Palm Beach and Collier Counties), United States, beginning in 2020, and in shipments of plant products originating from Colombia and entering the United States beginning in 2019, are identified as B. jafara Webb. This species was previously known only from the Seychelles and Aldabra Islands, which are parts of the Seychelles archipelago in the Indian Ocean east of mainland Africa. Identifications were made by comparison with type specimens, both morphologically and through molecular analysis. Specimens in Palm Beach Co. were swept from commercial rice (Oryza sativa L.) paddies. Mitochondrial cytochrome c oxidase I (COI) barcodes of specimens from Florida and Colombia were closely matched to each other and to partial barcodes obtained from paratype specimens of B. jafara. The COI barcodes also closely matched sequences from previously unidentified Balclutha specimens in the Barcode of Life Data Systems (BOLD) from Kenya and South Africa, several of which were confirmed later morphologically as B. jafara. Previously unidentified museum specimens from South Sudan, Zambia, and Zimbabwe were determined as B. jafara. Together, these specimens show that B. jafara has a more widespread African distribution than was known previously, and that it arrived in the Western Hemisphere by 2019. Balclutha jafara is redescribed and illustrated. Further studies on the Balclutha fauna of Florida were performed. COI barcode data were generated for Floridian specimens of B. caldwelli Blocker, B. curvata Caldwell, B. flavescens (Baker), B. frontalis (Ferrari), B. incisa (Matsumura), and B. lucida (Butler). A phylogenetic analysis of COI data was conducted using publicly available sequences and those generated here. A key to the Balclutha species known from Florida is provided. The names that have been applied and mis-applied to Western Hemisphere species are discussed. To clarify the identity of some species, illustrations are given for: the female holotype and a male paratype of Eugnathodus virescens Osborn (=B. flavescens); the holotype of Nesosteles robustus Caldwell (=B. robusta); and the holotype of Balclutha curvata Caldwell. Additional barcoded specimens of Balclutha from Kenya and Pakistan were provided for examination by the BOLD research group and determined as B. sujawalensis Ahmed, previously known only from India and Pakistan, and this species is also illustrated here.

Morphology, molecular phylogenetics, and DNA barcoding revealed a new unusual species of the aphid genus Pleotrichophorus from the USA (Insecta, Hemiptera: Aphididae).

Here, we present the descriptions of a new aphid species in the genus Pleotrichophorus Brner, 1930 (Hemiptera: Aphididae: Macrosiphini), found by Kenneth L. Hibbard, inspection supervisor for the Florida Department of Agriculture and Consumer Services, Division of Plant Industry. It is associated with Euthamia graminifolia (L.) Nutt. (Asteraceae) a native plant species in Florida, USA. Apterous and alate viviparous and oviparous females of Pleotrichophorus blackmani sp. n. are described and illustrated using light and scanning electron microscopy (SEM). SEM images of apterous viviparous female of Pleotrichophorus glandulosus (Kaltenbach, 1846), type species of the genus Pleotrichophorus, are given for the first time. Taxonomic notes are given, and an updated key to the apterae of the Euthamia-feeding aphids is provided. A multigene phylogenetic analyses of two New World Pleotrichophorus species places the genus in the tribe Macrosiphini sensu stricto. Pleotrichophorus glandulosus, the type species of the genus, was described from Germany. European specimens of P. glandulosus from France had similar molecular sequences to both Florida species, strongly suggesting that the new species belongs in Pleotrichophorus. COI and gnd sequence data indicate that P. blackmani sp. n. can be identified reliably by DNA barcodes.

A new gall-producing species of Geoica Hart, 1894 (Hemiptera: Aphididae: Eriosomatinae) from Israel.

Geoica inbari sp. nov., living on Pistacia palaestina Boiss. (Anacardiaceae), is described based on apterous fundatrigeniae, fall migrants, embryos of apterous exules within fall migrants (fundatrispuriae) and the first instar larva of an apterous exule borne by a fall migrant, collected in the Mount Hermon area of Northern Israel. The new species differs from all other known Geoica species in its mitochondrial DNA, and from those known from Pistacia by the shape of the galls. It makes coral-shaped galls, while all congeners produce spherical galls. The new species is a member of the Geoica utricularia group and morphologically resembles Geoica wertheimae Brown Blackman, 1994.

Description of a new species of Hamamelistes forming galls on Fothergilla spp. (Hamamelidaceae) and the generic limits of Hormaphidini (Sternorrhyncha: Aphididae: Hormaphidinae).

Hamamelistes and Hormaphis aphids of the tribe Hormaphidini are distributed disjunctly in eastern North America and Eurasia. Host-alternating species have life cycles encompassing generations in a gall on witch-hazel (Hamamelis spp.) and generations on leaves of birch (Betula spp.). In Hamamelistes, generations on witch-hazel induce globular pouch galls on flower or leaf buds. Herbarium specimens of a related Hamamelidaceae genus, Fothergilla, contain large galls in place of the seed head. We obtained a fresh sample of these elongate pouch galls collected from F. milleri in Alabama, USA. The galls were formed in place of fruiting structures and contained numerous aphids. Examination of morphology and the cytochrome oxidase subunit I barcode DNA sequence confirmed that the aphids are an undescribed species of Hamamelistes. Here, we describe the new species, Hamamelistes blackmani Dederich von Dohlen sp. n., from the morphology of foundresses, immatures, and winged forms in the gall. The life cycle is presumed monoecious. In addition, we review the evidence for including other genera in Hormaphidini and recommend that this tribe be restricted to Hamamelistes and Hormaphis.

Acquisition and Transmission of the Lethal Bronzing Phytoplasma by Haplaxius crudus Using Infected Palm Spear Leaves and Artificial Feeding Media.

Lethal bronzing (LB) is a fatal palm disease caused by the phytoplasma 'Candidatus Phytoplasma aculeata'. This disease causes significant economic losses in palm industries and landscapes. The American palm cixiid, Haplaxius crudus, recently was identified as the vector of the phytoplasma. However, knowledge about LB phytoplasma transmission is limited due to the lack of a method to generate phytoplasma-infected insects in the laboratory. In this study, the acquisition and transmission of the LB phytoplasma by H. crudus were investigated. Successful acquisitions of the phytoplasma by H. crudus were observed at 2 days acquisition access period on LB-infected palm spear leaves. Analyses revealed increased phytoplasma infection rates of H. crudus with longer acquisition access periods and latent periods. A significantly higher phytoplasma infection rate was shown after various acquisition access periods and latent periods than the infection rate of the field-collected H. crudus population. Transmission of the phytoplasma from LB-infected spear leaves to sucrose media by H. crudus also was observed using digital PCR assays. These results further support the vector status of H. crudus and offer valuable information to understand LB phytoplasma transmission. Additionally, these results generate a critical baseline for future LB phytoplasma-vector research by providing a way to generate vectors with high phytoplasma infection rates in the laboratory setting.

The Development and Evaluation of Insect Traps for the Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Psyllidae), Vector of Citrus Huanglongbing.

Citrus huanglongbing (HLB) is a severe problem for citrus cultivation. The disease management programs benefit from improved field tools suitable for surveying the ACP vector (Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae)) and the associated pathogen. In the present study, we utilize three-dimensional (3D) printers and design tools to develop traps that can capture and preserve ACPs. Three novel, 3D-printed traps were designed and evaluated: stem trap, and cylinder traps 1 and 2. The traps and yellow sticky cards were deployed weekly for 8 months in 2 non-commercial citrus groves in Florida; in California, the traps were evaluated for 12 months in field cages and 4 citrus groves. The stem traps captured lower numbers of ACPs at all experimental sites compared to the cylinder traps. Capture rates in the cylinder traps were comparable to the sticky trap, making the device a viable tool for monitoring field ACPs. The two main advantages of using the reusable 3D traps over standard methods of ACP and HLB surveys include dynamic sampling that can be conducted year-round and the capture of ACPs that can be preserved and tested. Improved trapping may facilitate quick management decisions and mitigate HLB.

Complex life histories predispose aphids to recent abundance declines.

Many animals change feeding habits as they progress through life stages, exploiting resources that vary in space and time. However, complex life histories may bring new risks if rapid environmental change disrupts the timing of these switches. Here, we use abundance times series for a diverse group of herbivorous insects, aphids, to search for trait and environmental characteristics associated with declines. Our meta dataset spanned three world regions and >300 aphid species, tracked at 75 individual sites for 10-50 years. Abundances were generally falling, with median changes of -8.3%, -5.6%, and -0.1% per year in the central USA, northwestern USA, and United Kingdom, respectively. Aphids that obligately alternated between host plants annually and those that were agricultural pests exhibited the steepest declines, relative to species able to persist on the same host plant year-round or those in natural areas. This suggests that host alternation might expose aphids to climate-induced phenology mismatches with one or more of their host plant species, with additional risks from exposure to insecticides and other management efforts. Warming temperatures through time were associated with milder aphid declines or even abundance increases, particularly at higher latitudes. Altogether, while a warming world appeared to benefit some aphid species in some places, most aphid species that had time-sensitive movements among multiple host plants seemed to face greater risk of decline. More generally, this suggests that recent human-induced rapid environmental change is rebalancing the risks and rewards associated with complex life histories.

Long-Term Field Evaluation Reveals Huanglongbing Resistance in Citrus Relatives.

Citrus huanglongbing (HLB) is a destructive disease with no known cure. To identify sources of HLB resistance in the subfamily Aurantioideae to which citrus belongs, we conducted a six-year field trial under natural disease challenge conditions in an HLB endemic region. The study included 65 Citrus accessions and 33 accessions belonging to 20 other closely related genera. For each accession, eight seedling trees were evaluated. Based on quantitative polymerase chain reaction analysis of the pathogen titers and disease symptoms, eight disease-response categories were identified. We report two immune, six resistant, and 14 tolerant accessions. Resistance and tolerance observed in different accessions may be attributed to a multitude of factors, including psyllid colonization ability, absence of pathogen multiplication, transient replication of the bacterium, lack of pathogen establishment in the plant, delayed infection, or recovery from infection. Most citrus cultivars were considered susceptible: 15 citrons, lemons, and limes retained leaves in spite of the disease status. Resistance and high levels of field tolerance were observed in many noncitrus genera. Disease resistance/tolerance was observed in Australian citrus relative genera Eremocitrus and Microcitrus, which are sexually compatible with citrus and may be useful in future breeding trials to impart HLB resistance to cultivated citrus.

Huanglongbing: An overview of a complex pathosystem ravaging the world's citrus.

Citrus huanglongbing (HLB) has become a major disease and limiting factor of production in citrus areas that have become infected. The destruction to the affected citrus industries has resulted in a tremendous increase to support research that in return has resulted in significant information on both applied and basic knowledge concerning this important disease to the global citrus industry. Recent research indicates the relationship between citrus and the causal agent of HLB is shaped by multiple elements, in which host defense responses may also play an important role. This review is intended to provide an overview of the importance of HLB to a wider audience of plant biologists. Recent advances on host-pathogen interactions, population genetics and vectoring of the causal agent are discussed.

The potato pest Russelliana solanicola Tuthill (Hemiptera: Psylloidea): taxonomy and host-plant patterns.

The Neotropical jumping plant-louse Russelliana solanicola Tuthill is a potato pest and a probable vector of plant pathogens. Populations morphologically similar to those found on potatoes have been collected on plants of at least ten different families, four of which have been confirmed as hosts by the presence of immatures. This suggests that R. solanicola is either a single polyphagous species or a complex of closely related, monophagous species (host races/cryptic species). Results of our analyses of multiple morphometric characters show for both sexes a grouping of the populations of R. solanicola and a clear separation of the latter from other Russelliana species. On the other hand, within R. solanicola, there is an overlap of populations from different host-plants as well as from different geographical regions. The results of the present study strongly suggest that R. solanicola is a single, polyphagous species and the known distribution indicates that it is native to the Andes. It is likely that R. solanicola has been introduced into eastern Argentina, Brazil and Uruguay. The polyphagy together with the ability to disperse and transmit plant pathogens potentially make this species an economically important pest of potato and other crop species.

Asymptomatic spread of huanglongbing and implications for disease control.

Huanglongbing (HLB) is a bacterial infection of citrus trees transmitted by the Asian citrus psyllid Diaphorina citri. Mitigation of HLB has focused on spraying of insecticides to reduce the psyllid population and removal of trees when they first show symptoms of the disease. These interventions have been only marginally effective, because symptoms of HLB do not appear on leaves for months to years after initial infection. Limited knowledge about disease spread during the asymptomatic phase is exemplified by the heretofore unknown length of time from initial infection of newly developing cluster of young leaves, called flush, by adult psyllids until the flush become infectious. We present experimental evidence showing that young flush become infectious within 15 d after receiving an inoculum of Candidatus Liberibacter asiaticus (bacteria). Using this critical fact, we specify a microsimulation model of asymptomatic disease spread and intensity in a grove of citrus trees. We apply a range of psyllid introduction scenarios to show that entire groves can become infected with up to 12,000 psyllids per tree in less than 1 y, before most of the trees show any symptoms. We also show that intervention strategies that reduce the psyllid population by 75% during the flushing periods can delay infection of a full grove, and thereby reduce the amount of insecticide used throughout a year. This result implies that psyllid surveillance and control, using a variety of recently available technologies, should be used from the initial detection of invasion and throughout the asymptomatic period.

Modeling huanglongbing transmission within a citrus tree.

The citrus disease huanglongbing (HLB), associated with an uncultured bacterial pathogen, is threatening the citrus industry worldwide. A mathematical model of the transmission of HLB between its psyllid vector and citrus host has been developed to characterize the dynamics of the vector and disease development, focusing on the spread of the pathogen from flush to flush (a newly developing cluster of very young leaves on the expanding terminal end of a shoot) within a tree. This approach differs from that of prior models for vector-transmitted plant diseases where the entire plant is the unit of analysis. Dynamics of vector and host populations are simulated realistically as the flush population approaches complete infection. Model analysis indicates that vector activity is essential for initial infection but is not necessary for continued infection because infection can occur from flush to flush through internal movement in the tree. Flush production, within-tree spread, and latent period are the most important parameters influencing HLB development. The model shows that the effect of spraying of psyllids depends on time of initial spraying, frequency, and efficacy of the insecticides. Similarly, effects of removal of symptomatic flush depend on the frequency of removal and the time of initiation of this practice since the start of the epidemic. Within-tree resistance to spread, possibly affected by inherent or induced resistance, is a major factor affecting epidemic development, supporting the notion that alternate routes of transmission besides that by the vector can be important for epidemic development.

Species composition of aphid vectors (Hemiptera: Aphididae) of barley yellow dwarf virus and cereal yellow dwarf virus in Alabama and western Florida.

Yellow dwarf is a major disease problem of wheat, Triticum aestivum L., in Alabama and is estimated to cause yield loss of 21-42 bu/acre. The disease is caused by a complex of viruses comprising several virus species, including Barley yellow dwarf virus-PAV and Cereal yellow dwarf virus-RPV. Several other strains have not yet been classified into a specific species. The viruses are transmitted exclusively by aphids (Hemiptera:Aphididae). Between the 2005 and 2008 winter wheat seasons, aphids were surveyed in the beginning of each planting season in several wheat plots in Alabama and western Florida Collected aphids were identified and bioassayed for their yellow dwarf virus infectivity. This survey program was designed to identify the aphid species that serve as fall vectors of yellow dwarf virus into winter wheat plantings. From 2005 to 2008, bird cherry-oat aphid, Rhopalosiphum padi (L.); rice root aphid, Rhopalosiphum rufiabdominale (Sasaki); and greenbug, Schizaphis graminum (Rondani), were found consistently between October and December. The species of aphids and their timing of appearance in wheat plots were consistent with flight data collected in North Alabama between 1996 and 1999. Both R. padi and R. rufiabdominale were found to carry and transmit Barley yellow dwarf virus-PAV and Cereal yellow dwarf virus-RPV. The number of collected aphids and proportion of viruliferous aphids were low. Although this study has shown that both aphids are involved with introduction of yellow dwarf virus to winter wheat in Alabama and western Florida, no conclusions can be made as to which species may be the most important vector of yellow dwarf virus in the region.

Lack of Evidence for Transmission of 'Candidatus Liberibacter asiaticus' Through Citrus Seed Taken from Affected Fruit.

Citrus huanglongbing, putatively caused by the associated bacterium 'Candidatus Liberibacter asiaticus', is the greatest threat to the world citrus industry today. The bacterium is spread locally and regionally by the citrus psyllid Diaphorina citri, and also can be disseminated by propagation of contaminated scion budwood that is grafted to the appropriate rootstock. The planting of 'Ca. Liberibacter asiaticus'-free trees is a component of a comprehensive strategy to manage huanglongbing. In contrast to the scion budwood, the rootstocks used to produce these trees are grown from seed. This research was undertaken to provide evidence as to whether or not 'Ca. L. asiaticus' can be transmitted through seed. Two groups of 360 or more seedlings each of various citrus species were grown from seed removed from fruit on trees that were symptomatic for huanglongbing and confirmed to be infected with 'Ca. L. asiaticus' by polymerase chain reaction (PCR) tests. These seedlings were tested multiple times over periods of up to 3 years. No symptoms typical of huanglongbing, such as blotchy leaf mottle, chlorotic shoots, or dieback of branches, were observed in these seedlings, and none of these 723 seedlings tested positive for the presence of 'Ca. L. asiaticus' even after repeated testing by sensitive quantitative PCR assays. Some sour orange seedlings did have quite pronounced and atypical growth, including stunting and mild to severe leaf malformation. These atypical growth habits were limited to seedlings that arose from zygotic embryos as determined by expressed-sequence tag simple-sequence repeat analyses. Thus, no evidence of transmission of 'Ca. L. asiaticus' via seed was obtained, and an earlier report of transmission of the pathogen through seed was not confirmed.

Distribution and Characterization of Citrus tristeza virus in South Florida Following Establishment of Toxoptera citricida.

The incidence of Citrus tristeza virus (CTV) was found to increase significantly in southern Florida within 2 years after the establishment of its most efficient vector, Toxoptera citricida (Kirkaldy). Increased incidence of both mild and severe strains was documented, with the incidence of severe strains increasing more than mild strains. Molecular probes capable of differentiating mild, quick decline and various types of stem-pitting strains demonstrated that trees often were infected with more than one strain of CTV, with trees containing up to five different strains. Some CTV strains detected in the southeast urban corridor of Florida and in commercial groves in southwest Florida were found to react with probes specific for stem-pitting strains known from elsewhere in the world. The implications of the presence of these CTV strains in Florida and their possible presence in citrus budwood scion trees are discussed.