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The African citrus psyllid, Trioza erytreae (Del Guercio) (Hemiptera, Triozidae), is native to tropical Africa and invasive species in North America and Europe. The main host plants are citrus, displaying a preference for lemon trees. This psyllid was recently detected in the northwest region of the Iberian Peninsula, both in Spain and Portugal. Here, we used a model combining a reaction-diffusion model to a stochastic long-distance dispersal model to simulate the invasion dynamics of T. erytreae in Portugal. The psyllid spread in Portugal was simulated between 2015 and 2021 for different combinations of model parameters: two fecundity levels; spread with and without stochastic long-distance dispersal; single or two introductions of T. erytreae; and considering or not the urban and peri-urban citrus trees, besides citrus orchards, estimated using Google Street view imagery. The incorporation of long-distance human mediated dispersal significantly improved the F1-score in the model validation using the official reports as the observed data. Concomitantly, the dispersal rate of T. erytreae in Portugal was on average about 66 km/year, whereas removing long-distance dispersal events, the observed mean was 7.8 ± 0.3 km/year. The dispersal was mainly towards the south along the coastline, where human population is concentrated. The inclusion of the estimated citrus trees outside orchards areas significantly increased the F1-score in the model validation, revealing the importance these isolated host plants hold as stepping stones for the species current invasion and possibly for other species alike.

It has been nearly 100 years since citrus growers in two distinct regions in the northern provinces of South Africa noticed unusual symptoms in their citrus trees, causing significant crop losses. They had no idea that these symptoms would later become part of an almost global pandemic of a disease called greening or huanglongbing (HLB). The rapid spread of the disease indicated that it might be caused by a transmissible pathogen, but it took >50 years to identify the causative agent as ‘Candidatus Liberibacter africanus’. Recently, the disease appeared in more African countries, spreading by both infected planting material and Trioza erytreae. To date, five ‘Ca. L. africanus’ subspecies have been identified in various rutaceous species, with ‘Ca. L. africanus subsp. clausenae’ the only subspecies for which a biovar was detected in citrus. Efforts to detect and differentiate HLB-causing Liberibacter species are ongoing, and recent developments are discussed here. This review focuses on aspects of the African form of HLB, including its specific bacterial species and subspecies, its main insect vector, its geographic distribution, and current management strategies.

Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) is one of the vectors of the citrus greening or huanglongbing (HLB) disease, the most devastating citrus disease globally. A classical biological control program has been established to control this vector in Europe, where it has been threatening the citrus industry since its detection in mainland Spain and Portugal. For this, its main parasitoid Tamarixia dryi (Waterson) (Hymenoptera: Eulophidae) has been introduced. Here, we evaluated the nutritional value of T. erytreae honeydew as a suitable food source for T. dryi. This solid honeydew is the most abundant food source for the parasitoid in the field. Our results demonstrated that T. erytreae honeydew enhanced the longevity of T. dryi compared to other diets such as water, ‘sucrose alone’ or ‘sucrose + protein’. Females fed on honeydew also oviposited more eggs than those fed on water or ‘sucrose alone’. Finally, T. dryi fed on honeydew tended to parasitize more psyllids than those fed on the other diets. Chemical analyses demonstrated that T. erytreae honeydew contains proteins, and this can explain the increase in egg load of honeydew fed parasitoids. Further research is necessary to understand why these females tended to parasitize more than females fed on ‘sucrose + protein’. Overall, these results contribute to understanding the successful and rapid establishment of T. dryi in Europe and to the successful rearing and release programs in newly invaded areas.

A luta biológica clássica é frequentemente usada para o controlo de surtos de pragas de grande impacto na agricultura e floresta, no entanto, deve ser suportada por uma intensa atividade de investigação que assegure o sucesso destes programas e evite efeitos secundários indesejados. Recentemente iniciou-se um plano de luta biológica para o controlo de Trioza erytreae (Hemiptera: Triozidae) com o himenóptero Tamarixia dryi. Porém o conhecimento sobre psilídeos (superfamília Psylloidea a que pertence T. erytreae) em Portugal é muito reduzido e, para a continuação das largadas com T. dryi neste programa, são necessários estudos sobre a praga e respetivo parasitoide em várias vertentes, entre elas, a diversidade de psilídeos e fauna auxiliar associada. Neste âmbito, foi iniciada uma prospeção no Algarve com o objetivo de inventariar os psilídeos presentes nesta região, nativos e introduzidos, determinar as suas plantas hospedeiras e averiguar a fauna auxiliar, em particular os seus parasitoides. Ao longo do trabalho, foram realizadas mais de 330 amostras, utilizando as técnicas das batidas e sweeping net bem como recolhas de material vegetal, em mais de 140 espécies de plantas. Comparando com os dados existentes na Psyl´list foram encontradas 24 plantas hospedeiras, das quais 3 detetadas pela primeira vez a nível nacional e 5 a nível mundial. No que diz respeito aos psilídeos encontrados durante a prospeção, pelo menos 32 morfoespécies foram identificadas, quase todas até ao género, e algumas até ao nível específico. Foram igualmente encontrados parasitoides em 7 destes psilídeos. Este é o primeiro estudo exaustivo realizado sobre psilídeos no Algarve o qual trouxe novos dados sobre a fauna desta superfamília, plantas hospedeiras e parasitoides. É um trabalho que requer, no entanto, uma continuação com o objetivo de proceder a uma identificação específica de todos os psilídeos encontrados e uma continuação e alargamento da prospeção iniciada. Surveying psyllids and their parasitoids in the South of Portugal Classical biological control is often used for the control of outbreaks of pests of great impact in agriculture and forestry. It must be, nevertheless, supported by intense research activity to ensure the success of these programs and avoid undesirable side effects. Recently a biological control plan was initiated to control Trioza erytreae (Hemiptera: Triozidae) with Tamarixia dryi. However, knowledge of psyllids (superfamily Psylloidea to which T. erytreae belongs) in Portugal is very limited and, in order to continue with the release of T. dryi in this program, studies on the pest and its parasitoid in various aspects are necessary, including the diversity of psyllids and associated auxiliary fauna. In this context, a survey was started in the Algarve with the aim of inventorying the psyllids present in this region, native and introduced, determining their host plants, and investigating the auxiliary fauna, in particular their parasitoids. Throughout the work, more than 330 samples were taken, using the beating and sweeping net techniques as well as collecting plant material, on more than 140 plant species. Compared to the existing data on Psyl'list, 24 host plants were found, of which 3 were detected for the first time at national level and 5 worldwide. Regarding psyllids found during the survey, at least 32 morphospecies were identified, almost all up to genus, and some up to specific level. Parasitoids were likewise found in 7 of these psyllids. This is the first comprehensive study carried out on psyllids in the Algarve which brought new data on the fauna of this superfamily, host plants and parasitoids. It is a work that nevertheless requires a follow-up in order to proceed to a specific identification of all the psyllids found and a continuation and extension of the prospection started. Esta dissertação insere-se no projeto Life Vida for Citrus LIFE18 CCA/ES/001109, financiado pela União Europeia.

The African citrus triozid Trioza erytreae Del Guercio (Hemiptera: Triozidae) is the most destructive citrus pest. Presently, biological data on T. erytreae are insufficient for important parameters like distribution, seasonal dynamics and entomopathogens. Therefore, we determined the temporal dynamics of T. erytreae along three different altitudinal gradients in Kenya. In low altitudes, females of T. erytreae reactivated and started laying eggs between late February and early March. The mean monthly number of immature stages of T. erytreae per flush shoot peaked in February, whereas adults peaked in March. For mid-altitudes, T. erytreae mean populations peaked in February, but adults were already present in December. In high altitudes, adults appeared in June, and females began laying eggs. Trioza erytreae population densities in shaded trees positively and significantly correlated with unshaded trees. There was a significant difference between adult density and maximum temperature, average temperature, solar radiation, evaporation and dew point. Furthermore, this study evaluated the effects of 11 Metarhizium anisopliae and 4 Beauveria bassiana fungal isolates against adult T. erytreae under laboratory conditions. Metarhizium anisopliae ICIPE 18 and ICIPE 69 were the most potent isolates, causing 97.5% and 82.5% mortalities within the shortest LT50 time of 4.4 and 5.9 days, respectively. The presence of Diaphorina citri Kuwayama (Hemiptera: Liviidae) on Zanthozylum capense requires further investigation. Our findings provide relevant information for early detection, monitoring and developing biopesticides against the pest.

Huanglongbing (HLB) is one of the most catastrophic citrus diseases. HLB pathogensCandidatusLiberibacter asiaticus (Las),Ca. L. africanus (Laf), andCa. L. americanus (Lam) and their insect vectors Asian citrus psyllids (ACP,Diaphorina citri) and African citrus psyllids (AfCP,Trioza erytreae) are invading citrus producing regions where HLB was absent previously, including the Mediterranean basin. Importantly, the Mediterranean region is one of the two major citrus producing areas without HLB. Here, I provide a short perspective regarding a) information related to the distribution of the HLB pathogens and psyllid vectors in this region and neighboring countries, b) predicted distribution of the HLB for this region, c) the possible evolution of Liberibacters and how they could have established their relationship with different hosts, and d) approaches to fend off HLB. Specifically, I emphasized the following measurements: quarantine measures against AfCP, ACP, Las, Laf, and Lam, early detection and diagnosis of HLB and removal of inoculum, surveillance of AfCP and ACP and eradication of citrus psyllids once identified.

El huanglongbing (HLB) o greening de los cítricos es una enfermedad bacteriana que limita seriamente la producción de cítricos en la mayor parte de zonas citrícolas mundiales. Afortunadamente tanto la enfermedad como los dos principales insectos que transmiten esta enfermedad, los psílidos Trioza erytreae y Diaphorina citri, no están presentes en la citricultura mediterránea española. Trabajos recientes han demostrado como la acción del HLB puede limitarse mediante la activación de las defensas de las plantas, principalmente las desencadenadas a partir de la ruta de señalización del ácido salicílico (SA).

This report provides an assessment of citrus health globally. Citrus trees are a perennial crop grown for its fruits, which are one of the key sources of vitamin C in human diets (Liu et al 2012), a source of simple sugars, dietary fibre and secondary metabolites (Lv et al 2015), and a key ingredient in juices, jams, jellies and marmalades. Citrus fruits and by-products from juice production are also used to extract essential oils and citric acids used in the food, cosmetics and pharmaceutical industries (Kaur et al 2021; Panwar et al 2021). It is estimated that around 2/3 of citrus fruits produced worldwide are consumed as fresh fruit, and the remaining 1/3 is used mainly for juice production and some industrial purposes (Liu et al 2012).

El presente estudio está enmarcado dentro del proyecto LIFE18 CCA/ES/001109, encaminado a instaurar estrategias de control sostenible de Trioza erytreae (Del Guercio) (vector del HLB) y otras plagas de importancia para la citricultura, en el contexto del Pacto Verde Europeo. El objetivo se ha centrado en el diseño y gestión de infraestructuras ecológicas como estrategia de Control Biológico por Conservación para aumentar la biodiversidad de la entomofauna útil asociada al agrosistema de los cítricos. Los ensayos se han desarrollado en 5 áreas de cultivo de cítricos, localizadas en diferentes zonas citrícolas, norte y sur de Tenerife y Gran Canaria.

Huanglongbing (HLB) is the most devastating citrus disease and is associated with three bacterial species of the genus &lsquo, Candidatus Liberibacter&rsquo, transmitted by insect vectors. The early detection of HLB is based on PCR methods, and it is one of the cornerstones for preventing incursion into disease-free countries. However, the detection of phytopathogenic bacteria with PCR-based methods is problematic in surveys that include a variety of samples of different origins. Here, we first report the proportion of amplifications obtained by two standardized real-time PCR methods for the diagnosis of HLB in various environmental samples that include plants, psyllid vectors, and parasitic wasps of the psyllids. The results of 4915 samples showed that 9.3% of them were amplified by the first rapid screening test and only 0.3% by the more specific tests. Most of the amplifications were associated with parasitic wasps. We designed the primers external to the target regions of both real-time PCR protocols to determine if amplifications belonged to one of three &lsquo, Ca. Liberibacter&rsquo, species associated with HLB. The bioinformatic analysis of the sequences obtained with these primers revealed that all these amplifications came from the presence of other prokaryotic organisms in the samples. The primers developed in this study overcome the problem of undesired amplification in environmental samples. Thus, they could be used in future survey protocols to prevent the eradication of negative trees and the generation of unjustified alarms.

Trioza erytreae (Del Guercio) is one of the psyllid insect vectors of the causal agents of huanglongbing. This paper proposes an assessment of the effectiveness of several pesticides with and without a pine oil-based organic adjuvant, in order to contain the spread and population of this pest and reduce the side effects on the Tamarixia dryi parasitoid. Five insecticides and their combinations with pine oil were sprayed against T. erytreae on citrus trees under semi-field and field conditions. The effect of the same treatments was assessed on T. dryi under laboratory conditions. All insecticides, except for acetamiprid, increased their effectiveness when combined with pine oil under both conditions. Cyantraniliprole, dimethoate, and their respective combinations with the organic adjuvant showed the highest efficacies against T. erytreae. Under laboratory conditions, dimethoate reported the most negative effect on T. dryi activity whereas cyantraniliprole and its combination with pine oil yielded a low toxicity effect on this parasitoid. Our results recommend the development of an integrated control approach for citrus growers based on an insecticide rotation program, preventing the emergence of pest resistance to one substance. In this sense, other insecticides, such as lambda-cyhalothrin with pine oil adjuvant or acetamiprid, could be considered.

Turunçgil yeşillenme hastalığı (Huanglongbing-HLB, Greening Disease) turunçgil ağaçlarında ekonomik kayıplara neden olan bakteriyel bir hastalıktır. Hastalığı oluşturan patojenin bilimsel ismi Candidatus liberibacter’dir. HLB ye sebep olan şu ana kadar üç farklı Candidatus tür’ü saptanmıştır. Bunlardan Candidatus liberibacter asiaticus (CLas), dünya genelinde HLB ile ilişkili en yaygın Liberibacter türüdür. Diğer iki tür olan, Candidatus liberibacter americanus (CLam) ve Candidatus liberibacter africanus (CLaf) ise daha az yoğunlukta ve ekolojilere özel olarak yaygınlık gösterirler. Hastalık Hindistan’da 1929 yılında “turunçgillerde geriye ölüm” olarak tanımlanmıştır. Ancak bu hastalık 1890’lı yıllarda Çin de ‘yellow shoot diseas, sarı sürgün hastalığı’ olarak çok iyi bilinmekte olması nedeniyle çoğu bilim insanı hastalığın ilk ortaya çıktığı yeri Çin olarak kabul etmektedir. Turunçgil yeşillenme hastalığına karşı bugüne kadar yüzde yüz etkili herhangi bir mücadele yöntemi bulunamamıştır. Bu da, patojenin ne kadar tehlikeli ve önemli olduğunu ortaya koymaktadır. Hastalık, turunçgil üretim alanlarında veya ülkeler arasında vektör böceklerle, (Afrika Turunçgil Psillidi olan Trioza erytreae Del Guercio, diğer bir Psillid türü olan Asya Psillidi Diaphorina citri Kuwayama) veya enfekteli aşı gözleri ile taşınmaktadır. HLB, özellikle portakal, mandarin, tangelo ve greyfurt fidan veya ağaçlarında yaşa bakmaksızın etkilidir. Enfekteli ağaçlarda ortaya çıkan tipik hastalık belirtileri çinko eksikliği, bazı abiyotik stres faktörlerinin belirtileri veya diğer bazı turunçgil hastalıklarının oluşturduğu belirtiler ile karıştırılabilmektedir., Citrus greening disease (Huanglongbing-HLB) is a bacterial diseasecauses economic losses on citrus trees. The scientific name of the causal agentis Candidatus liberibacter. Three Candidatusspecies have identified so far. Candidatusliberibacter asiaticus (CLas) is the most common Liberibacter species whichis associated with HLB disease in the world. Candidatus liberibacter americanus (CLam) and Candidatus liberibacter africanus (CLaf) is observed less than CLas becausethey require specific ecological environments. Bacterial disease described in 1929 inIndia as citrus die back. However,the bacterial disease has already been known in China as yellow shoot in the 1890s.There is no 100% effective management methods controling this devastatingwidespread disease. It reveals that citrus greening is very dangerous andimportant disease. The disease can be disseminated via vectors, African Citrus Psyllid (Trioza erytreae Del Gue), other Psyllid species (Asian Citrus Psyllid (Diaphorina citri Kuwayama), or infectedbud grafting. Especially, HLB is an effective disease on orange, mandarin,tangelo and grapefruit seedlings or trees regardless of age. Typical infected tree symptoms can beconfused with zinc deficiency, some abiotic stress factors, or some othercitrus diseases symptoms.

The African citrus triozid (ACT), Trioza erytreae Del Guercio, is a destructive pest particularly on citrus, and vectors, “Candidatus” Liberibacter africanus (CLaf), which is the causal agent of the African citrus greening disease. Our study seeks to establish the distribution and host‐plant relationship of ACT across citrus production areas in Kenya. We also modelled the risk of spread using the maximum entropy modelling algorithm with known occurrence data. Our results infer that ACT is widely distributed and causes severe damage to four alternative host plants belonging to the family Rutaceae. The adults, immature stages (eggs and nymphs), galls and the percentage of infested leaves were significantly higher in shaded than unshaded trees. However, adult ACTs preferred Kenyan highlands to Victoria Lake and coastal regions. The average area under the curve of the model predictions was 0.97, indicating an optimal model performance. The environmental variables that most influenced the prediction were the precipitation of wettest quarter, precipitation of wettest month, mean diurnal range, temperature seasonality and mean temperature of the coldest quarter. The current prediction of ACT exceeded its existing range, especially in the Western, Nyanza, Central, Rift valley and Eastern regions of Kenya. The model predicted a contraction of suitable habitats for a potential spread in 2040 with an inland shift to higher altitudes in the cooler regions. The potential for further expansion to climatically suitable areas was more pronounced for the 2080 forecast. These findings provide relevant information to improve monitoring/surveillance and designing IPM strategies to limit its spread and damage.

Trioza erytreae per se is a major citrus pest, although its destructive power is much greater as a vector of the non-culturable bacterium ‘Candidatus Liberibacter africanus’ causing the most devastating disease of citrus worldwide: the citrus huanglongbing (HLB). Following early detections of T. erytreae in mainland Europe, simultaneously in Portugal and Spain in 2014, its distributional range has rapidly increased, thus becoming a serious threat to the entire Mediterranean citrus industry. In 2018, one year after our latest survey, the situation has only worsened, with T. erytreae being around 200 km closer to key citrus growing areas in southern Portugal and Spain. Once T. erytreae invades a new area, the degree of severity of its attacks increases very quickly, which is indicative of its potential for invasiveness. We highlight that T. erytreae is currently spread and well established along the northwestern coast of the Iberian Peninsula, ranging from Cedeira in A Coruna (Spain) to Pontes/Setubal in Portugal, covering approximately 600 km on a straight uninterrupted line. Implementation of further containment and control measures are critical to addressing this growing risk.

Trioza erytreae (Del Guercio, 1918) (Hemiptera: Triozidae) is a vector of Candidatus Liberibacter spp., the causal agent of Huanglongbing disease (HLB). This study evaluates the preference of T. erytreae in different citrus seedlings. Thus, six different non-grafted citrus rootstocks were used for these experiments: (a) Carrizo citrange, (b) Citrus macrophylla, (c) ‘Cleopatra’ mandarin, (d) Forner-Alcaide No. 5, (e) Forner-Alcaide No. 517, and (f) Poncirus trifoliata (‘Flying Dragon’). The behaviour and survival of this psyllid was evaluated through the feeding preference of T. erytreae adults for different rootstocks (in a choice trial under greenhouse conditions) and oviposition and survival of T. erytreae adults on the different citrus material (in a no-choice trial under laboratory conditions). Trioza erytreae showed a clear preference for hosting and feeding on C. macrophylla, and Carrizo citrange was the most suitable rootstock for insect reproduction and survival followed by C. macrophylla. Conversely, Poncirus trifoliata was the least attractive rootstock to T. erytreae adults in the greenhouse trial and led to significantly lower T. erytreae survival. Our results suggest that conventional citrus rootstocks, such as Carrizo citrange and C. macrophylla, could increase T. erytreae populations.

The African citrus psyllid, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae), is a vector of Candidatus Liberibacter africanus (CLaf), a pathogen that causes huanglongbing (HLB) in Africa. Trioza erytreae has invaded areas of Asia and Europe and has threatened citrus production due to its biological habits and the transmission of CLaf. Mexico is a country where citrus production has a vital role from the economic and social point of view. Therefore, ecological niche modeling (ENM) was used to determine if Mexico has the environmental availability that will allow T. erytreae invasion. We analyzed whether or not the distribution of Casimiroa edulis La Llave (Rutaceae) in the country could be a factor that enables the dispersal of T. eytreae. The environmental connectivity between five points of entry into the country (two ports and three airports) was explored to determine possible routes of dispersal of T. erytrae. The results showed that Mexico has wide availability for the invasion of the African citrus psyllid, which coincides with essential citrus areas of the country and with the distribution of C. edulis. Of the entry points studied, the Port of Veracruz showed nearby areas with environmental connectivity. Preventive monitoring measures for T. erytreae in Mexico should focus on Veracruz state because it has an entry point, ideal environmental availability, citrus areas, and specimens of C. edulis.

Trioza erytreae is one of the vectors of Huanglongbing (HLB), the main global citrus groves threat. Since its recent detection in the north-western Iberian Peninsula (Spain and Portugal), its contention and eradication have been a priority to prevent its spread. For the biological control of T. erytreae, it is important to understand the role that each potential natural enemy could have. With the aim to determine which predators have incorporated T. erytreae into their diet, a PCR-based method has been developed for the specific detection of T. erytreae in their gut contents. For this, a pair of specific primers was designed from the mitochondrial cytochrome c oxidase subunit I (COI) region. Specificity of this pair of primers was studied and feeding trials with two predator species were conducted to determine the decay rates of T. erytreae within their gut. None of the non-target species was amplified, showing the high specificity of these T. erytreae primers. Feeding trials showed 4.8h and 4.5h half-life time detections of T. erytreae ingested by Chrysoperla carnea and Cryptolaemus montrouzieri, respectively. Finally, field-collected generalist predators of T. erytreae-infested citrus trees from the Canary Islands and Galicia (Spain), were analysed by conventional PCR for the presence of T. erytreae in their guts. Results showed that a wide range of predator taxa ingested the target prey, like the families Coccinellidae, Anthocoridae, Chrysopidae, Hemerobiidae, Forficulidae, Miridae, Syrphidae, Formicidae, Erythraeidae and the order Araneae, with detection percentages ranging from 20 to 100%. These results confirm that most of the analysed generalist predators found in citrus trees could be potential candidates for the biological control of T. erytreae in future biological control programs of this HLB vector. info:eu-repo/semantics/acceptedVersion

Psyllids, also known as jumping plant lice, are phloem feeding Hemiptera that often show a strict species-specific relationship with their host plants. When psyllid-plant associations involve economically important crops, this may lead to the recognition of a psyllid species as an agricultural or horticultural pest. The Australian endemic tea tree, Melaleuca alternifolia (Maiden & Betche) Cheel., has been used for more than a century to extract essential oils and, long before that, as a traditional medicine by Indigenous Australian people. Recently, a triozid species has been found to damage the new growth of tea trees both in Queensland and New South Wales, raising interest around this previously undocumented pest. Furthermore, adults of the same species were also collected from Citrus plantations, leading to potential false-positive records of the exotic pest Trioza erytreae (Del Guercio 1918), the African Citrus psyllid. Here we describe for the first time Trioza melaleucae Martoni sp. nov. providing information on its distribution, host plant associations and phylogenetic relationships to other Trioza species. This work enables both morphological and molecular identification of this new species, allowing it to be recognized and distinguished for the first time from exotic pests as well as other Australian native psyllids. Furthermore, the haplotype network analysis presented here suggests a close relationship between Trioza melaleucae and the other Myrtaceae-feeding Trioza spp. from Australia, New Zealand, and Taiwan.

The African citrus psyllid Trioza erytreae is one of the major threats to citrus industry as the vector of the incurable disease known as huanglongbing (HLB) or citrus greening. The psyllid invaded the northwest of the Iberian Peninsula 6 years ago. The invasion alarmed citrus growers in the Mediterranean basin, the largest citrus producing area in Europe, which is still free of HLB. Before our study, no research had been carried out on the genetic diversity of T. erytreae populations that have invaded the Iberian Peninsula and the archipelagos of the Macaronesia (Madeira and the Canary Islands). In this study, combining microsatellites markers and mtDNA barcoding analysis, we characterize the genetic diversity, structure and maternal relationship of these new invasive populations of T. erytreae and those from Africa. Our results suggest that the outbreaks of T. erytreae in the Iberian Peninsula may have derived from the Canary Islands. The populations of T. erytreae that invaded Macaronesia and the Iberian Peninsula are likely to have originated from southern Africa. We anticipate our results to be a starting point for tracking the spread of this invasive pest outside of Africa and to be important for optimizing contingency and eradication plans in newly invaded and free areas.

Tras la presentación de la Estrategia De la Granja a la Mesa, la agricultura de la Unión Europea se encuentra en un importante proceso de transformación hacia modelos de producción más sostenibles. Los cambios en los modelos de gestión de plagas y enfermedades no están exentos de controversia, ya que muchas de las herramientas de control químico más utilizadas están desapareciendo. En el presente artículo se revisa cuál es el estado actual de la gestión de las principales plagas y enfermedades de nuestra citricultura, bajo este nuevo contexto planteado por la Comisión Europea.

El psílido africano de los cítricos Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) se detectó en la península ibérica (Galicia y Portugal) a finales de 2014. Este psílido es uno de los dos principales vectores de las bacterias que producen el huanglongbing o greening, una enfermedad incurable de los cítricos, que no se ha detectado ni en España ni en Portugal. En el año 2017 se inició un programa de controlbiológico clásico para introducir y liberar el parasitoide Tamarixia dryi (Waterston) (Hymenoptera: Eulophidae) con el fin de mejorar el control de este psílido. En este artículo se presentan las sueltas realizadas y los primeros resultados obtenidos en campo tras la liberación del parasitoide en Galicia. El parasitoide se liberó de forma experimental en tres localidades de Pontevedra en otoño 2019 y primavera de 2020. Los muestreos realizados por TRAGSATEC en Galicia por encargo del Servicio de Sanidad y Producción Vegetal de la Comunidad Autónoma de Galicia y el Instituto Valenciano de Investigaciones Agrarias (IVIA) muestran que T. dryi se ha establecido, muestra niveles altos de parasitismo en los puntos de suelta y se está dispersando sin afectar a otras especies de psílidos presentes en Galicia.

Trioza erytreae, the African citrus psyllid, is a vector of Candidatus Liberibacter spp., the causal agent of the citrus greening disease or Huanglongbing (HLB). The spread of the vector throughout the Iberian Peninsula has been continuous since its introduction in mainland Spain in 2014. The patterns of host preference and feeding behaviour largely depend on olfactory cues. Understanding these patterns is crucial to prevent further dispersion and develop management measures against the pest. In this work, a series of settlement, olfactometric, probing, and feeding experiments were conducted to assess the host preference of T. erytreae for lemon or bitter orange plants. The settlement experiment provided evidence on the preference of both sexes of T. erytreae for lemon plants, whereas males did not show any significant choice pattern in the case of the olfactometric assays. Forty EPG variables were analysed to describe and compare the probing and feeding behaviour of T. erytreae on lemon and bitter orange plants. The EPG variables indicated that T. erytreae has some difficulties in accepting the phloem of bitter orange plants. This suggests that lemon plants would be a better source for the acquisition of Candidatus Liberibacter asiaticus (CLas) by T. erytreae since the psyllid spends much longer periods feeding from the phloem on lemon than on bitter orange. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The authors are grateful to the European Union grant, programme H2020 entitled: PRE-HLB: Preventing HLB epidemics for ensuring citrus survival in Europe. H2020- SFS-2018–2 Topic SFS-05–2018-2019–2020—new and emerging risks to plant health (Project nº 817526) as well as to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020). info:eu-repo/semantics/publishedVersion

The “citrus greening disease” or huanglongbing is caused by the Gram-negative bacterium Candidatus liberibacter spp. One vector of HLB, the African citrus psyllid Trioza erytreae (del Guercio, 1918), was recorded for the first time in 2014 in mainland Spain and since then it has spread throughout the Iberian Peninsula. Measures against T. erytreae include chemical treatments and quarantine although eradication programmes have been of limited success or even failed. The biological control of T. erytreae has been little developed yet. Among natural enemies, spiders may encompass a promising group of predators. The objective of this work was to assess the potential of spiders as natural enemies of T. erytreae. A Citrus limon orchard was selected in northwestern Portugal in the area colonized by T. erytreae. A total of 100 webs (50 above and 50 below 1.5 m) were visually inspected throughout the orchard in August 2020. The family of the web-builder, web size, number of adults of T. erytreae captured by each web, and the temperature and humidity were registered. Temperature and humidity did not significantly differ between the two vertical strata. Web size was significantly higher in the lower strata whereas the number of captured adults of T. erytreae was significantly higher in the upper strata. The dominant family in the upper strata was Theridiidae corresponding with the most successful webs capturing adults of T. erytreae. Our results suggest that web architecture was the only factor driving the number of captured adults of T. erytreae. Thus, space web builders could be the most successful natural enemies of T. erytreae among aerial web builders.

Huanglongbing (HLB, Asian Citrus Greening), the most devastating disease of citrus has not been detected in southern Africa (Gottwald, 2010). HLB is associated with 'Candidatus Liberibacter asiaticus' (CLas), a phloem-limited bacterium vectored by Diaphorina citri Kuwayama (Hemiptera: Liviidae), the Asian Citrus Psyllid (ACP). African Citrus Greening, associated with 'Candidatus Liberibacter africanus' (CLaf) and its vector the African Citrus Triozid, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae), are endemic to Africa, although not previously reported from Angola. African Greening is less severe than HLB, largely due to heat sensitivity of CLaf and its vector. Introduction of HLB into southern Africa would be devastating to citrus production in commercial and informal sectors. Concern was raised that CLas or ACP might hae inadvertently been introduced into Angola. In July 2019, a survey was conducted in two citrus nurseries in Luanda and Caxito and in different orchards on 7 farms surrounding Calulo and Quibala. Yellow sticky traps for insects were placed at the various localities and collected after c. 3 weeks. Breeding signs of T. erytreae (pit galls) were observed on citrus in some locations, but no insect vectors were detected on traps. Trees were inspected for signs and symptoms of citrus pests and diseases, particularly those that resemble HLB (foliar blotchy mottle, shoot chlorosis, vein yellowing and corking, lopsided fruit with aborted seeds and colour inversion) and its vectors (pit galls on leaves or waxy exudates). Leaves and shoots with suspect symptoms were sampled for laboratory analysis (43 samples). DNA was extracted from petiole and midrib tissue of leaves using a modified CTAB extraction protocol of Doyle and Doyle (1990). Real-time PCR was done using universal Liberibacter primers of Roberts et al. (2015), CLaf specific primers of Li et al. (2006) and CLas specific primers of Bao et al. (2019). All real-time PCR protocols indicated the presence of CLaf in 6 samples (Tab. S1). CLas or other citrus Liberibacter species were not detected. The presence of CLaf in sample 37 was confirmed by constructing a library (NEXTFLEX® DNA Sequencing Kit, PerkinElmer) with extracted DNA and performing high-throughput sequencing on an Ion Torrent™ S5™ platform (Central Analytical Facility, Stellenbosch University). To improve the quality of the reads, all 233,617,700 obtained reads were trimmed from the 3' end to a maximum length of 240 nt using Trimmomatic (Bolger et al. 2014). The high quality reads were mapped to the Citrus sinensis reference genome (NC_023046.1) using Bowtie 2.3.4 (Langmead and Salzberg 2012) to subtract all the reads that had high identity to the host plant (number of mismatches allowed in the seed was set to 1). The 14,691,369 unmapped reads (6.2% of original data) were mapped to the CLaf reference genome NZ_CP004021.1 using CLC Genomics Workbench 10.1.1 (Qiagen) (Length fraction = 0.8; Similarity fraction = 0.9). A CLaf consensus genome was generated that spanned 99.7% of the reference genome and the 163001 mapped reads had a 22.9 mean read coverage. The consensus sequence was 99.7% identical to NZ_CP004021.1 and was submitted to Genbank as accession: CP054879. The positive CLaf detections were from trees with typical HLB or African Citrus Greening symptoms, viz. lopsided fruit with green stylar ends, aborted seed and stained columella at base of fruit button; yellow shoots with leaves showing symptoms of blotchy mottle and vein yellowing and corking (Fig. S1) in a commercial citrus farm outside Calulo and included 2 'Ponkan' mandarin (C. reticulata), 2 Valencia and 1 'Navelina' tree (C. sinensis), and a citrus nursery in Luanda (1 lime tree; C. aurantifolia) (Tab. S1). This first report of CLaf in Angola highlights the need to prevent spread by removing infected trees and managing the insect vector, as well as the need for further surveys to determine the occurrence of African Greening and its vectors in other provinces and to confirm the absence of exotic citrus pests and diseases. References Bao, M. et al. 2020. Plant Dis. 104:527 Bolger, A. M. et al. 2014. Bioinformatics. 30:2114-2120. Doyle, J.J. and Doyle, J.L. 1990. Focus 12:13 Gottwald, T.R. 2010. Annu. Rev. Phytopathol. 48:119 Langmead, B. and Salzberg, S. 2012. Nature Methods. 9:357-359. Li, W. et al. 2006. Jnl. Microbiol. Methods 66:104 Roberts, R. et al. 2015. Int. J. Syst. Evol. Micr. 65:723.

Trioza erytreae is the main vector for ‘Candidatus Liberibacter africanus’, the causative agent of African Citrus Greening disease. The insect is widespread in Africa, and has recently disseminated to Southwestern Europe. This study aimed at generating reference mitogenome sequences for T. erytreae, as a background for future genetic diversity surveys. Complete mitochondrial sequences of three specimens collected in Ethiopia, Uganda and South Africa were recovered using Ion Torrent technology. The mitogenomes of T. erytreae from Uganda and Ethiopia were highly similar, and distinct from that found in South Africa. The phylogeographic structure of T. erytreae was assessed using genetic clustering and pairwise distances, based on a dataset of public COI sequences recorded as T. erytreae. The dataset revealed ten haplotypes with strong phylogeographic structure in Africa and Europe. Three haplotypes found in Kenya on Clausena anisata belonged to pairs separated by distances as high as 11.2%, and were basal to all other sequences. These results indicate that not all sequences identified as T. erytreae belong to the same species, and that some degree of specificity with different plant hosts is likely to exist. This study provides new baseline information on the diversity of T. erytreae, with potential implications for the epidemiology of African Citrus Greening disease.

The common white sapote, Casimiroa edulis occurs both wild and cultivated in central Mexico and produced in a different part of Ethiopia as home garden fruit crop for consumption as food. People also consider the fruits as one of the stimulant fruit crop. Currently, African citrus psyllids (Trioza erytreae) became one of the important pests of C. edulis in Ethiopia. The distribution and severity of this pest were recorded with an irregular pattern in the eastern part of Ethiopia. From all surveyed area (except some districts of Dire Dawa), very high infestation with high population density were recorded. The pest is currently in Ethiopia. This is first record of Trioza erytreae as devastating pest of casimir trees in Ethiopia. It is worth reporting to promote coordinated efforts amongst stakeholders, research specialists and extension officers to create awareness for proper management of the pest.

African citrus psyllid (Trioza erytreae (Del Guercio)) is a vector insect of the bacterium Candidatus Liberibacter africanus, the putative causal agent of Huanglongbing, the most devastating citrus disease in the world. The insect was found on the island of Madeira in 1994 and in mainland Portugal in 2015. Present in the north and center of the country, it is a threat to Algarve, the main citrus-producing region. Trioza erytreae eggs and first instar nymphs are sensitive to the combination of high temperatures and low relative humidity. Daily maximum air temperature and minimum relative humidity data from 18 weather stations were used to calculate the water vapor pressure deficit (vpd) from 2004 to 2018 at various locations. Based on the mean vpd and the number of unfavorable days (vpd &lt, 34.5 and vpd &lt, 56 mbar) of two time periods (February to May and June to September), less favorable zones for T. erytreae were identified. The zones with thermal and water conditions like those observed in the Castelo Branco and Portalegre (Center), Beja (Alentejo), Alte, and Norinha (Algarve) stations showed climatic restrictions to the development of eggs and first instar nymphs of African citrus psyllid. Effective control measures, such as the introduction and mass release of Tamarixia dryi (Waterson), a specific parasitoid, and chemical control are necessary in favorable periods for T. erytreae development, such as in spring and in areas with limited or no climate restrictions.

African citrus greening (ACGD) and huanglongbing (HLB) diseases are the most damaging diseases of citrus worldwide. Currently, the disease has no cure and has been attributed to the collapse of the citrus industry in several countries. In Africa, the causative agent “Candidatus” Liberibacter africanus is vectored by African citrus triozid (ACT) Trioza erytreae Del Guercio (Hemiptera: Triozidae). African citrus triozid is native to Africa but has been recently reported in Asia and Europe. Apart from citrus, Murraya koenigii (L.) and Clausena anisata (Willd) Hook. F. ex Benth. are also considered as preferred host plants. At present, there is scant information on host plant suitability and preference of T. erytreae. Also, there are contradictory reports on its reproduction and survival on rutaceous and non‐rutaceous host plants. In the present study, we tested the suitability and preference of rutaceous and non‐rutaceous trees and shrubs as potential ACT host plants in choice and no‐choice bioassays. The development from egg to the adult stage was longest on Calodendrum capense (Wright & Arn.) Engl. Host plants of superior quality accordingly to several ACT's biological parameters measured also revealed significantly higher morphometric characteristics. Our findings on the host status of the five rutaceous plants imply that these plants can greatly influence the population dynamics of ACT as well as the epidemiology of ACGD, and these can be a useful guide in the area‐wide management of the pest in Kenya.

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

Huanglongbing (HLB) is by far the most devastating disease of citrus crops across the world, because it promotes a progressive weakening of citrus trees (until death in around 10 years) that also involves a sudden loss of their production capacity. The African psyllid Trioza erytreae, one of the two known vectors of the bacteria causing HLB, is present in the northwestern Iberian Peninsula since 2014. Since a previous survey done in 2015 showed a considerably spread of this psyllid towards both north and south, a large-scale survey in the subsequent two years was carried out in order to know its current distributional range, population density and, thus the effectiveness of contingency plans. Our results evidence a growing number of new affected areas throughout the Iberian Peninsula, as well as a stronger severity of T. erytreae attacks, which currently occurs from San Xiao (Spain) to Maiorca (Portugal), over 400 km of coastline. The greater ability of T. erytreae to reach new areas may be due to the existence of higher outbreaks and population densities, which represents a serious threat for the nearing citrus-producing areas. If no effective control and management measures are implemented, it seems unavoidable that T. erytreae will spread across Europe.

Huanglongbing (HLB) is the most destructive disease of citrus worldwide. The disease is caused by Candidatus Liberibacter spp., which is vectored by the psyllids Diaphorina citri Kuwayama and Trioza erytreae. Secretory proteins are important in bacterial pathogenesis and structure components. Some of them are expressed at a high level. To obtain the highly-expressed secretory protein genes (SPGs) for antiserum preparation, six candidate SPGs were chosen from Candidatus Liberibacter asiaticus by bioinformatic analysis and were further tested by qPCR and RT-qPCR methods, respectively. The result showed that two SPGs, 408 and pap (both are Flp pilus assembly protein genes), have relative high amounts of DNA and RNA transcripts of early HLB-infected green orange leaves. The 408 and pap genes were further constructed into the plant expression vector pCAMBIA1300 (GV1300: GFP) and expressed in tobacco leaf epidermal cells for subcellular localization analysis. The transient expression results indicated that the 408 protein is located in the nuclei and cytoplasm of tobacco leaf cells. However, the pap protein is located in the cytoplasm of tobacco leaf cells, which may help the pathogen invade into plant cells. This research is an important foundation for the preparation of the antiserum against Candidatus Liberibacter asiaticus and the early detection of HLB disease.

Citrus (Citrus spp.) production continues to decline in East Africa, particularly in Kenya and Tanzania, the two major producers in the region. This decline is attributed to pests and diseases including infestation by the African citrus triozid, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae). Besides direct feeding damage by adults and immature stages, T. erytreae is the main vector of 'Candidatus Liberibacter africanus', the causative agent of Greening disease in Africa, closely related to Huanglongbing. This study aimed to generate a novel barcode reference library for T. erytreae in order to use DNA barcoding as a rapid tool for accurate identification of the pest to aid phytosanitary measures. Triozid samples were collected from citrus orchards in Kenya, Tanzania, and South Africa and from alternative host plants. Sequences generated from populations in the study showed very low variability within acceptable ranges of species. All samples analyzed were linked to T. erytreae of GenBank accession number KU517195. Phylogeny of samples in this study and other Trioza reference species was inferred using the Maximum Likelihood method. The phylogenetic tree was paraphyletic with two distinct branches. The first branch had two clusters: 1) cluster of all populations analyzed with GenBank accession of T. erytreae and 2) cluster of all the other GenBank accession of Trioza species analyzed except T. incrustata Percy, 2016 (KT588307.1), T. eugeniae Froggatt (KY294637.1), and T. grallata Percy, 2016 (KT588308.1) that occupied the second branch as outgroups forming sister clade relationships. These results were further substantiated with genetic distance values and principal component analyses.

Diaphorina citri Kuwayama, also known as the Asian citrus psyllid, is a pest of citrus known for its transmission of Candidatus Liberibacter asiaticus (Ca. L. asiaticus), the causal bacterium of Huanglongbing. The African citrus triozid Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) has been the putative vector of Candidatus Liberibacter africanus (Ca. L. africanus) which causes the African citrus greening disease, until the recent detection of D. citri on the continent. Following reports of D. citri in Kenya and Tanzania, we surveyed citrus plants to establish the presence/absence of D. citri in Ethiopia in citrus-growing regions ranging from 900 to 2,460 m above sea level (masl). Diaphorina citri adults were detected in five of the surveyed sites in Ethiopia. Adult insects encountered were collected using an aspirator and stored in 97% ethanol. The mitochondrial cytochrome oxidase 1 (mt COI) gene of the collected insects was amplified using LepF1/LepR1 primers, and sequences obtained showed low variation, which fell within the acceptable range of species. BLAST was used to query the sequences obtained, and all the sequences linked to D. citri accessions that are available in GenBank. The analysis of the sequences revealed a new haplotype of the species that differs from haplotypes previously reported. Phylogenetic relationships of our samples and other D. citri reference sequences was inferred using the Maximum-likelihood method. Monophyly was observed between the samples and the publicly available sequences from global accessions. This is the first report of the presence of D. citri in Ethiopia.

Huanglongbing (HLB) (citrus greening disease) is one of the most serious bacterial diseases of citrus. It is caused by (1) Candidatus Liberibacter africanus, transmitted by Trioza erytreae and (2) C.L. asiaticus and C.L. americanus, transmitted by Diaphorina citri. As part of a multidisciplinary project on D. citri (www.citrusgreening.org), we made a detailed study, using micro-computed tomography, of the female abdominal terminalia, reproductive system (ovaries, accessory glands, spermatheca, colleterial (= cement) gland, connecting ducts, and ovipositor) and bacteriome, which we present here. New terms and structures are introduced and described, particularly concerning the spermatheca, ovipositor and bacteriome. The quality of images and bacteriome reconstructions are comparable, or clearer, than those previously published using a synchrotron or fuorescence in situ hybridisation (FISH). This study: reviews knowledge of the female reproductive system and bacteriome organ in D. citri; represents the frst detailed morphological study of D. citri to use micro-CT; and extensively revises existing morphological information relevant to psylloids, hemipterans and insects in general. High quality images and supplementary videos represent a signifcant advance in knowledge of psylloid anatomy and are useful tools for future research and as educational aids., Kansas State University (KSU) S15192.01, University of Granada, USDA-NIFA S15192.01 2014-70016-23028

© 2020 by the authors., Assessing the potential of spread of an introduced crop pest in a new country is crucial to anticipating its effects on crop production and deriving phytosanitary management toward reducing potential negative effects. Citrus production represents a key agricultural activity throughout the Mediterranean basin. The African citrus psyllid Trioza erytreae (del Guercio, 1918) (Hemiptera: Triozidae) is a natural vector of Candidatusliberibacter spp., the causal agent of the harmful disease huanglongbing (HLB) or “citrus greening disease”. In continental Europe, T. erytreae was detected for the first time in northwestern Spain in 2014. Pest risk analysis (PRA) approaches, such as modeling, consider both time and space components to predict the potential distribution of pests in a given region. In this work, we aim to parameterize a model able to predict the expected spread of T. erytreae in the Iberian Peninsula using three types of PRA models. The kernel model with two hypothetical entry points accurately predicted the distribution of T. erytreae with respect to latitude. This model should be further refined and validated to support decision-makers in the adoption of timely and successful management and regulatory measures against the spread of T. erytreae to other citrus-producing areas in Europe., The authors are grateful to the Foundation for Science and Technology (FCT, Portugal), for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020) and to the project PRE-HLB—Preventing HLB epidemics for ensuring citrus survival in Europe (H2020-SFS-2018-2 Topic SFS-05-2018-2019-2020, proj. No. 817526).

El psílido africano de los cítricos Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) es uno de los dos principales vectores de las bacterias que producen el huanglongbing o greening, una enfermedad incurable de los cítricos. Este vector está presente en las Islas Canarias desde 2002 y en la península ibérica (Galicia y Portugal) desde finales de 2014, sin que se haya detectado la bacteria. En 2017 se inició un programa de control biológico clásico para introducir y liberar el parasitoide Tamarixia dryi (Waterston) (Hymenoptera: Eulophidae) con el fin de mejorar el control del psílido. En este artículo se presentan los primeros resultados obtenidos en campo tras la liberación del parasitoide en las Islas Canarias. El parasitoide se liberó de forma experimental en la localidad de Valle de Guerra en la isla de Tenerife en la primavera de 2018. Los muestreos realizados por el Servicio de Sanidad Vegetal del Gobierno Canario muestran que T. dryi se dispersó rápidamente por toda la isla de Tenerife, así como por las islas vecinas de Gran Canaria, La Palma, La Gomera y El Hierro. En este artículo se repasan algunas de las características de este parasitoide y cómo su liberación ha afectado a las poblaciones de T. erytreae en las Islas Canarias.