@article{armstrong_doud_luo_raithore_baldwin_zhao_plotto_bai_manthey_stover_et al._2021, title={Beneficial horticultural responses from the application of solar thermotherapy to mature Huanglongbing-affected citrus trees}, volume={7}, ISSN={["2468-0141"]}, DOI={10.1016/j.hpj.2021.04.008}, abstractNote={The detrimental effects of Huanglongbing (HLB) on citrus are well known and so is the need for effective methods to combat this disease. Solar thermotherapy (ST), one of the management methods to help alleviate some of the negative effects of HLB, is the process of heating trees to therapeutic temperatures by encompassing the tree within a plastic structure (Visqueen) to harness the sun's natural energy. ST was applied to mature ‘Valencia’ citrus trees in three locations. Tree vigor, yield, and Candidatus Liberibacter asiaticus (Las) titer in leaves were monitored for two consecutive seasons post ST treatment, while fruit and juice quality were evaluated at the end of the second season. ST promoted an increase in canopy density in most groves tested and did not have a significant effect on fruit quantity, despite the prolonged exposure of the trees to increased temperatures. Moreover, Las titer was reduced in both leaves and juice processed from affected trees post ST. With respect to fruit quality, the ratio of total soluble solids to titratable acidity was higher post ST compared to controls as was the sucrose content of the juice in most treated groves, whereas limonin was higher in juice from control trees. Principal components analysis of aroma volatiles showed significant differences between juice from treated versus control trees with volatiles imparting top-note and freshness to orange juice, such as acetaldehyde, hexanal, Z-3-hexenol and linalool, being higher in juice from treated trees. Taste panels confirmed that flavor differences existed, ultimately showing that ST resulted in improved juice flavor in well-managed groves. Although the effects of ST on the trees appear temporary, such outcomes emphasize its utility when used as part of an integrated management strategy for HLB-affected citrus, imparting beneficial horticultural responses with minimal to positive effects on subsequent juice flavor.}, number={5}, journal={HORTICULTURAL PLANT JOURNAL}, author={Armstrong, Cheryl M. and Doud, Melissa S. and Luo, Weiqi and Raithore, Smita and Baldwin, Elizabeth A. and Zhao, Wei and Plotto, Anne and Bai, Jinhe and Manthey, John A. and Stover, Ed and et al.}, year={2021}, month={Sep}, pages={411–422} }
 @article{qian_wang_zhang_sun_luo_posny_xu_tang_ma_zhang_et al._2021, title={Investigation of proline in superficial scald development during low temperature storage of 'Dangshansuli' pear fruit}, volume={181}, ISSN={["1873-2356"]}, DOI={10.1016/j.postharvbio.2021.111643}, abstractNote={The role of proline in superficial scald development in pear fruit was investigated in this study. During low temperature storage of ‘Dangshansuli’ pear fruit, superficial scald incidence and index accumulated in association with the alternation of α-farnesene and conjugated trienols (CTols). 14 out of 17 free amino acids were identified; proline content gradually decreased, which was consistent with the up-regulation of PbrP5CS activity and down-regulation of PbrProDH activity in its metabolic pathway. A total of 14 genes involved in proline metabolism were identified based on transcriptome annotation with diverse expression profiles. Results from correlation analysis among proline content further indicate that enzyme activity and gene expression profile, PbrProDH2, PbrProDH4, PbrProDH5 & PbrP5CS5 might play a critical role in proline metabolism during low temperature storage of ‘Dangshansuli’ fruit; thus, influencing superficial scald development which was then functionally validated using the transgenic pear fruit. Postharvest 1-MCP and diphenylamine (DPA) treatment inhibited the accumulation of CTols, and thus, mitigated superficial scald development and maintained higher proline content, in association with the up-regulated PbrP5CS activity, PbrP5CS4 & PbrP5CS5 mRNAs as well as the down-regulated PbrProDH activity & PbrProDH4 transcripts. In a further study, we found that exogenous application of proline alleviated superficial scald incidence and index. To that end, the results of our study confirmed that proline was involved in superficial scald development during pear storage.}, journal={POSTHARVEST BIOLOGY AND TECHNOLOGY}, author={Qian, Ming and Wang, Libin and Zhang, Suling and Sun, Liqiong and Luo, Weiqi and Posny, Drew and Xu, Shanshan and Tang, Chao and Ma, Min and Zhang, Chen and et al.}, year={2021}, month={Nov} }
 @article{gottwald_taylor_amorim_bergamin-filho_bassanezi_silva_fogliata_fourie_graham_hattingh_et al._2021, title={Probabilistic risk-based model for the assessment of Phyllosticta citricarpa-infected citrus fruit and illicit plant material as pathways for pathogen introduction and establishment}, volume={142}, ISBN={1873-6904}, DOI={10.1016/j.cropro.2020.105521}, abstractNote={Citrus Black Spot (CBS), caused by the ascomycete, Phyllosticta citricarpa, is a fruit, foliar, and twig spotting fungal disease affecting the majority of commercial cultivars of citrus. The disease causes cosmetic lesions, may cause fruit drop and P. citricarpa is considered a quarantine pathogen by some countries, impacting domestic and international trade of citrus fruit. Regulatory requirements affecting fruit trade exist even though there is no documented case of disease spread via infected fruit into previously disease-free areas. To clarify the risk of fruit as a potential pathway for the spread of CBS, we developed a quantitative, probabilistic risk assessment model. The model provides an assessment of all steps in the fruit pathway, including production, packinghouse handling, transportation, export-import distribution channels, and consumer endpoints. The model is stochastic and uses Monte Carlo simulation to assess the risk of P. citricarpa moving through all steps in the pathway. We attempted to use all available literature and information to quantitate risk at each point in the potential pathway and by sequentially linking all steps to determine the overall quantitative risk. In addition, we assessed climatological effects on incidence of diseased fruit at production sites and on fungal reproduction and infection, as well as criteria for establishment at endpoints. We examined ten case studies between exporting and importing locations/countries. Model results indicated fruit to be an epidemiologically insignificant means for CBS spread, even between producing countries where CBS occurs and CBS-free importing countries with disease-conducive climates. We created a second model to examine the introduction of infected plant material from countries where CBS occurs. This model demonstrated significant probability of introduction via such infected material. However, pathogen establishment and disease development was still restricted only to areas with conducive climatological conditions. We created a tool to quantitatively explore the viability of various potential pathways via combinations of CBS-present production sites and corresponding pathway endpoints, including environments conducive and non-conducive to CBS. The tool is provided to aid decision makers on phytosanitary risk relative to international trade of citrus fruit.}, journal={CROP PROTECTION}, author={Gottwald, T. R. and Taylor, E. L. and Amorim, L. and Bergamin-Filho, A. and Bassanezi, R. B. and Silva, Jr. G. J. and Fogliata, G. and Fourie, P. H. and Graham, J. H. and Hattingh, V. and et al.}, year={2021}, month={Apr} }
 @article{gottwald_poole_taylor_luo_posny_adkins_schneider_mcroberts_2020, title={Canine Olfactory Detection of a Non-Systemic Phytobacterial Citrus Pathogen of International Quarantine Significance}, volume={22}, ISSN={["1099-4300"]}, DOI={10.3390/e22111269}, abstractNote={For millennia humans have benefitted from application of the acute canine sense of smell to hunt, track and find targets of importance. In this report, canines were evaluated for their ability to detect the severe exotic phytobacterial arboreal pathogen Xanthomonas citri pv. citri (Xcc), which is the causal agent of Asiatic citrus canker (Acc). Since Xcc causes only local lesions, infections are non-systemic, limiting the use of serological and molecular diagnostic tools for field-level detection. This necessitates reliance on human visual surveys for Acc symptoms, which is highly inefficient at low disease incidence, and thus for early detection. In simulated orchards the overall combined performance metrics for a pair of canines were 0.9856, 0.9974, 0.9257 and 0.9970, for sensitivity, specificity, precision, and accuracy, respectively, with 1–2 s/tree detection time. Detection of trace Xcc infections on commercial packinghouse fruit resulted in 0.7313, 0.9947, 0.8750, and 0.9821 for the same performance metrics across a range of cartons with 0–10% Xcc-infected fruit despite the noisy, hot and potentially distracting environment. In orchards, the sensitivity of canines increased with lesion incidence, whereas the specificity and overall accuracy was >0.99 across all incidence levels; i.e., false positive rates were uniformly low. Canines also alerted to a range of 1–12-week-old infections with equal accuracy. When trained to either Xcc-infected trees or Xcc axenic cultures, canines inherently detected the homologous and heterologous targets, suggesting they can detect Xcc directly rather than only volatiles produced by the host following infection. Canines were able to detect the Xcc scent signature at very low concentrations (10,000× less than 1 bacterial cell per sample), which implies that the scent signature is composed of bacterial cell volatile organic compound constituents or exudates that occur at concentrations many fold that of the bacterial cells. The results imply that canines can be trained as viable early detectors of Xcc and deployed across citrus orchards, packinghouses, and nurseries.}, number={11}, journal={ENTROPY}, author={Gottwald, Timothy and Poole, Gavin and Taylor, Earl and Luo, Weiqi and Posny, Drew and Adkins, Scott and Schneider, William and McRoberts, Neil}, year={2020}, month={Nov} }
 @article{gottwald_poole_mccollum_hall_hartung_bai_luo_posny_duan_taylor_et al._2020, title={Canine olfactory detection of a vectored phytobacterial pathogen, Liberibacter asiaticus, and integration with disease control}, volume={117}, ISSN={["0027-8424"]}, url={https://publons.com/wos-op/publon/39596623/}, DOI={10.1073/pnas.1914296117}, abstractNote={Early detection and rapid response are crucial to avoid severe epidemics of exotic pathogens. However, most detection methods (molecular, serological, chemical) are logistically limited for large-scale survey of outbreaks due to intrinsic sampling issues and laboratory throughput. Evaluation of 10 canines trained for detection of a severe exotic phytobacterial arboreal pathogen, Candidatus Liberibacter asiaticus ( C Las), demonstrated 0.9905 accuracy, 0.8579 sensitivity, and 0.9961 specificity. In a longitudinal study, cryptic C Las infections that remained subclinical visually were detected within 2 wk postinfection compared with 1 to 32 mo for qPCR. When allowed to interrogate a diverse range of in vivo pathogens infecting an international citrus pathogen collection, canines only reacted to Liberibacter pathogens of citrus and not to other bacterial, viral, or spiroplasma pathogens. Canines trained to detect C Las-infected citrus also alerted on C Las-infected tobacco and periwinkle, C Las-bearing psyllid insect vectors, and C Las cocultured with other bacteria but at C Las titers below the level of molecular detection. All of these observations suggest that canines can detect C Las directly rather than only host volatiles produced by the infection. Detection in orchards and residential properties was real time, ∼2 s per tree. Spatiotemporal epidemic simulations demonstrated that control of pathogen prevalence was possible and economically sustainable when canine detection was followed by intervention (i.e., culling infected individuals), whereas current methods of molecular (qPCR) and visual detection failed to contribute to the suppression of an exponential trajectory of infection.}, number={7}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Gottwald, Timothy and Poole, Gavin and McCollum, Thomas and Hall, David and Hartung, John and Bai, Jinhe and Luo, Weiqi and Posny, Drew and Duan, Yong-Ping and Taylor, Earl and et al.}, year={2020}, month={Feb}, pages={3492–3501} }
 @article{hilf_luo_2020, title={Inoculation Period and Citrus Host Effect Establishment of New Infections of 'Candidatus Liberibacter asiaticus' Transmitted via Vegetative Grafting}, volume={104}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-09-19-2022-RE}, abstractNote={Vegetative grafting is a common method of transmitting and propagating ‘Candidatus Liberibacter asiaticus’, the bacterial species accepted as the causal agent of the citrus disease huanglongbing (HLB). Generally, infected tissue that is grafted to a receptor tree remains in place indefinitely to ensure transmission. In this study, individual HLB-symptomatic leaves were grafted as ‘Ca. L. asiaticus’ inoculum sources to receptor trees of six citrus types and removed after an inoculation period (IP) of 21, 51, or 81 days. The goal was to assess the effect of varying IPs on transmission of bacteria to the receptor tree and on the successful establishment of a new infection. Survival analysis of data from three trials showed a significantly reduced proportion of infected trees with an IP of 21 days compared with IPs of 51 and 81 days but that there was no significant difference in the proportion of infected trees between IPs of 51 and 81 days. In addition, the time to first detection of pathogen DNA in an infected tree was delayed significantly for the 21-day IP when compared with the 51- and 81-day IPs. Survival analysis showed that the probability of infection of sweet orange trees was significantly higher than for trees of five other citrus types throughout the experiment. There was no significant difference between the infection probabilities of these latter five citrus types. The data from this study show that successful infection by grafting is dependent upon the time of exposure to the inoculum, that shorter IPs increase the time needed to establish a systemic infection, and that citrus types vary in their overall susceptibility to infection by ‘Ca. L. asiaticus’.}, number={7}, journal={PLANT DISEASE}, author={Hilf, Mark E. and Luo, Weiqi}, year={2020}, month={Jul}, pages={1894–1899} }
 @article{luo_posny_kriss_graham_poole_taylor_mccollum_gottwald_bock_2020, title={Seasonal and post-harvest population dynamics of the Asiatic citrus canker pathogen Xanthomonas citri subsp. citri on grapefruit in Florida}, volume={137}, ISSN={["1873-6904"]}, DOI={10.1016/j.cropro.2020.105227}, abstractNote={Asiatic citrus canker (ACC, caused by Xanthomonas citri subsp. citri, [Xcc]) is a serious disease of citrus, reducing yield and impacting marketability of fresh fruit. ACC has phytosanitary implications for fresh fruit trade. Lesions on fruit, leaves, and shoots in an orchard of ACC-susceptible grapefruit were monitored for production of Xcc from June to the following January in 2009 and 2010. Lesions on fruit post-harvest either packingline-treated or not treated were also monitored for production of Xcc on fruit harvested in November 2013 and January 2014. Shoot lesions generally produced fewer bacteria and had a smaller proportion of active lesions compared to leaf and fruit lesions. As the season progressed the proportion of active lesions on fruit and shoots gradually declined. Bacterial flux density (BFD) in surviving lesions was >103 on all organs at all sample times. A window-pane analysis revealed weather variables associated with bacterial survival within the lesion. The packingline treatment had no effect in reducing the proportion of active lesions, and had only a small, transient effect reducing BFD (~1.5 log units). Lesion size affected survival – small lesions (<10 mm2) declined in activity more rapidly compared to larger lesions, both in the field pre-harvest, and post-harvest in storage. Although lesions of ACC on fruit, leaves, and shoots are a constant source of inoculum, steps that can be taken to minimize early infection of fruit which often results in larger lesions will reduce the risk of inoculum dispersal. Current packingline treatments do not reduce activity of lesions of ACC. Based on these and other previously reported results, lesions on fruit post-harvest can be deemed a limited risk for spread of canker.}, journal={CROP PROTECTION}, author={Luo, Weiqi and Posny, Drew and Kriss, Alissa B. and Graham, Jim H. and Poole, Gavin H. and Taylor, Earl L. and McCollum, Greg and Gottwald, Tim R. and Bock, Clive H.}, year={2020}, month={Nov} }
 @article{gottwald_luo_posny_riley_louws_2019, title={A probabilistic census-travel model to predict introduction sites of exotic plant, animal and human pathogens}, volume={374}, ISSN={["1471-2970"]}, url={http://dx.doi.org/10.1098/rstb.2018.0260}, DOI={10.1098/rstb.2018.0260}, abstractNote={International travel offers an extensive network for new and recurring human-mediated introductions of exotic infectious pathogens and biota, freeing geographical constraints. We present a predictive census-travel model that integrates international travel with endpoint census data and epidemiological characteristics to predict points of introduction. Population demographics, inbound and outbound travel patterns, and quantification of source strength by country are combined to estimate and rank risk of introduction at user-scalable land parcel areas (e.g. state, county, zip code, census tract, gridded landscapes (1 mi 2 , 5 km 2 , etc.)). This risk ranking by parcel can be used to develop pathogen surveillance programmes, and has been incorporated in multiple US state/federal surveillance protocols. The census-travel model is versatile and independent of pathosystems, and applies a risk algorithm to generate risk maps for plant, human and animal contagions at different spatial scales. An interactive, user-friendly interface is available online (https://epi-models.shinyapps.io/Census_Travel/) to provide ease-of-use for regulatory agencies for early detection of high-risk exotics. The interface allows users to parametrize and run the model without knowledge of background code and underpinning data. This article is part of the theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control’. This theme issue is linked with the earlier issue ‘Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes’.}, number={1776}, journal={PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={Gottwald, Tim and Luo, Weiqi and Posny, Drew and Riley, Tim and Louws, Frank}, year={2019}, month={Jul} }
 @article{serra_mckenzie_luo_osborne_2019, title={First report of Bemisia tabaci Mediterranean (biotype Q) (Hemiptera: Aleyrodidae) in the Dominican Republic}, volume={102}, ISSN={["1938-5102"]}, DOI={10.1653/024.102.0417}, abstractNote={MED was detected for the first time in the Dominican Republic from 2 provinces (Santo Domingo and Santiago), 2 host plants (tomato and tobacco), and 2 environments (greenhouse and open field). All MED sequences were identical and determined to be of Eastern Mediterranean origin. MEAM1 was the predominant B. tabaci cryptic species present, and was detected in all but 1 sample, which was 100% MED. NW was detected twice on eggplant in different geographical regions, and once on Mexican prickly poppy in a native habitat, but always with MEAM1.}, number={4}, journal={FLORIDA ENTOMOLOGIST}, author={Serra, Colmar and McKenzie, Cindy L. and Luo, Weiqi and Osborne, Lance S.}, year={2019}, month={Dec}, pages={778–782} }
 @misc{mcroberts_figuera_olkowski_mcguire_luo_posny_gottwald_2019, title={Using models to provide rapid programme support for California's efforts to suppress Huanglongbing disease of citrus}, volume={374}, ISSN={["1471-2970"]}, DOI={10.1098/rstb.2018.0281}, abstractNote={We describe a series of operational questions posed during the state-wide response in California to the arrival of the invasive citrus disease Huanglongbing. The response is coordinated by an elected committee from the citrus industry and operates in collaboration with the California Department of Food and Agriculture, which gives it regulatory authority to enforce the removal of infected trees. The paper reviews how surveillance for disease and resource allocation between detection and delimitation have been addressed, based on epidemiological principles. In addition, we describe how epidemiological analyses have been used to support rule-making to enact costly but beneficial regulations and we highlight two recurring themes in the programme support work: (i) data are often insufficient for quantitative analyses of questions and (ii) modellers and decision-makers alike may be forced to accept the need to make decisions on the basis of simple or incomplete analyses that are subject to considerable uncertainty. This article is part of the theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control’. This theme issue is linked with the earlier issue ‘Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes’.}, number={1776}, journal={PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={McRoberts, Neil and Figuera, Sara Garcia and Olkowski, Sandra and McGuire, Brianna and Luo, Weiqi and Posny, Drew and Gottwald, Tim}, year={2019}, month={Jul} }
 @article{wang_luo_sun_qian_2018, title={Changes in flavor-relevant compounds during vine ripening of tomato fruit and their relationship with ethylene production}, volume={59}, ISSN={["2211-3460"]}, DOI={10.1007/s13580-018-0067-2}, number={6}, journal={HORTICULTURE ENVIRONMENT AND BIOTECHNOLOGY}, author={Wang, Libin and Luo, Weiqi and Sun, Xiuxiu and Qian, Chunlu}, year={2018}, month={Dec}, pages={787–804} }
 @article{hilf_luo_2018, title={Dynamics of 'Candidatus Liberibacter asiaticus' Colonization of New Growth of Citrus}, volume={108}, ISSN={["1943-7684"]}, DOI={10.1094/PHYTO-12-17-0408-R}, abstractNote={‘Candidatus Liberibacter asiaticus’ is a phloem-colonizing intracellular bacterial pathogen of citrus associated with the disease huanglongbing. A study of patterns of colonization and bacterial population growth in new growth of different citrus types was conducted by pruning infected citron, sweet orange, sour orange, mandarin, citrange, and Citrus macrophylla trees to force the growth of axillary and adventitious shoots. The first three leaves on newly emerged shoots were collected at 30, 60, and 90 days to assess colonization and population growth of ‘Ca. L. asiaticus’ using real time PCR (qPCR). Single trials were conducted with mandarin and citron, two trials each for citrange, sour orange and sweet orange, and four trials for C. macrophylla. In citron the proportion of colonized leaves increased significantly over time, with 67, 85, and 96% of leaves colonized at 30, 60, and 90 days, respectively. For the other citrus types, the exact proportion of colonized leaves differed, but colonization exceeded 60% in mandarin, sour orange, and citrange, and exceeded 80% at 30 days in two trials with sweet orange and three trials with C. macrophylla, but there was no significant increase in the proportion of colonized leaves at 60 and 90 days. Bacteria were readily detected by 30 days in new leaves of all citrus types. Differences in the growth of the bacterial population between citrus types and at different times of the year were noted, but common trends were apparent. In general, bacterial titers peaked at 60 days, except in leaves of C. macrophylla where bacterial titers peaked at 30 days. The early and consistently high proportion of leaf colonization observed for new growth of sweet orange during two trials and for C. macrophylla during three trials indicates a near synchronous colonization of new leaves by 30 days.}, number={10}, journal={PHYTOPATHOLOGY}, author={Hilf, Mark E. and Luo, Weiqi}, year={2018}, month={Oct}, pages={1165–1171} }
 @article{ding_allen_luo_zhang_duan_2018, title={Molecular mechanisms underlying heat or tetracycline treatments for citrus HLB control}, volume={5}, ISSN={["2052-7276"]}, DOI={10.1038/s41438-018-0038-x}, abstractNote={Huanglongbing (HLB), a destructive plant bacterial disease, severely impedes worldwide citrus production. In our previous reports, we revealed the molecular mechanisms of host plant responses that underlie thermotherapy against HLB. In this study, we investigated the molecular mechanism underlying heat or tetracycline treatments on the HLB bacterium, ‘Candidatus Liberibacter asiaticus’ (Las) by focusing on Las prophage/phage conversion under stress conditions. By comparing the prophage FP1 and FP2 copy number to the copy number of 16S rDNA in HLB-affected plants, we found that the relative copy number of both FP1 and FP2 increased significantly, ranging from 3.4- to 6.7-fold change when Las-infected samples underwent a temperature shift from 23 to 37, 42 or 45 °C. When treated with tetracycline at 50–150 and 200–250 µg/ml, respectively, the relative copy number of both FP1 and FP2 increased by 3.4- to 6.0-fold. In addition, analyses of Las prophage structural gene and antirepressor gene copy numbers showed similar trends for all treatments. Furthermore, transmission electron microscopy provided direct evidence of lysogenic to lytic conversion upon temperature increase. These results not only provide new insight into the molecular mechanisms underlying heat or tetracycline treatment but also suggest a novel HLB control strategy by enhancing the endogenous conversion from Las prophages to phages.}, journal={HORTICULTURE RESEARCH}, author={Ding, Fang and Allen, Victoria and Luo, Weiqi and Zhang, Shouan and Duan, Yongping}, year={2018}, month={Jun} }
 @article{doud_wang_hoffman_latza_luo_armstrong_gottwald_dai_luo_duan_2017, title={Solar thermotherapy reduces the titer of Candidatus Liberibacter asiaticus and enhances canopy growth by altering gene expression profiles in HLB-affected citrus plants}, volume={4}, ISSN={["2052-7276"]}, DOI={10.1038/hortres.2017.54}, abstractNote={Huanglongbing (HLB), a systemic and destructive disease of citrus, is associated with ‘Candidatus Liberibacter asiaticus’ (Las) in the United States. Our earlier work has shown that Las bacteria were significantly reduced or eliminated when potted HLB-affected citrus were continuously exposed to high temperatures of 40 to 42 °C for a minimum of 48 h. To determine the feasibility and effectiveness of solar thermotherapy in the field, portable plastic enclosures were placed over commercial and residential citrus, exposing trees to high temperatures through solarization. Within 3–6 weeks after treatment, most trees responded with vigorous new growth. Las titer in new growth was greatly reduced for 18–36 months after treatment. Unlike with potted trees, exposure to high heat did not eradicate the Las population under field conditions. This may be attributed to reduced temperatures at night in the field compared to continuous high temperature exposure that can be maintained in growth chambers, and the failure to achieve therapeutic temperatures in the root zone. Despite the presence of Las in heat-treated commercial citrus, many trees produced abundant flush and grew vigorously for 2 to 3 years after treatment. Transcriptome analysis comparing healthy trees to HLB-affected citrus both before and after heat treatment demonstrated that post-treatment transcriptional expression patterns more closely resembled the expression patterns of healthy controls for most differentially expressed genes and that genes involved with plant-bacterium interactions are upregulated after heat treatment. Overall, these results indicate that solar thermotherapy can be an effective component of an integrated control strategy for citrus HLB.}, journal={HORTICULTURE RESEARCH}, author={Doud, Melissa M. and Wang, Yungsheng and Hoffman, Michelle T. and Latza, Christina L. and Luo, Weiqi and Armstrong, Cheryl M. and Gottwald, Tim R. and Dai, Liangying and Luo, Feng and Duan, Yongping}, year={2017}, month={Sep} }
 @article{mccollum_hilf_irey_luo_gottwald_2016, title={Susceptibility of Sixteen Citrus Genotypes to 'Candidatus Liberibacter asiaticus'}, volume={100}, ISSN={["1943-7692"]}, DOI={10.1094/pdis-08-15-0940-re}, abstractNote={Huanglongbing (HLB) disease is the most serious threat to citrus production worldwide and, in the last decade, has devastated the Florida citrus industry. In the United States, HLB is associated with the phloem-limited α-proteobacterium ‘Candidatus Liberibacter asiaticus’ and its insect vector, the Asian citrus psyllid (ACP; Diaphorina citri). Significant effort is being put forth to develop novel citrus germplasm that has a lower propensity to succumb to HLB than do currently available varieties. Effective methods of screening citrus germplasm for susceptibility to HLB are essential. In this study, we exposed small, grafted trees of 16 citrus types to free-ranging ACP vectors and ‘Ca. L. asiaticus’ inoculum in the greenhouse. During 45 weeks of exposure to ACP, the cumulative incidence of ‘Ca. L. asiaticus’ infection was 70%. Trees of Citrus macrophylla and C. medica were most susceptible to ‘Ca. L. asiaticus’, with 100% infection by the end of the test period in three trials, while the complex genetic hybrids ‘US 1-4-59’ and ‘Fallglo’ consistently were least susceptible, with approximately 30% infection. Results obtained in this greenhouse experiment showed good agreement with trends observed in the orchard, supporting the validity of our approach for screening citrus germplasm for susceptibility to HLB.}, number={6}, journal={PLANT DISEASE}, author={McCollum, Greg and Hilf, Mark and Irey, Mike and Luo, Weiqi and Gottwald, Tim}, year={2016}, month={Jun}, pages={1080–1086} }
 @article{gottwald_wierenga_luo_parnell_2013, title={Epidemiology of Plum pox 'D' strain in Canada and the USA}, volume={35}, ISSN={["1715-2992"]}, DOI={10.1080/07060661.2013.844733}, abstractNote={The successful 10-year eradication programme for Plum pox virus (PPV) in Pennsylvania, USA was based on vigilant surveys followed by removal of all Prunus spp. within 500 m of confirmed PPV-positive trees, resulting in declaration of eradication in October 2009. In comparison, in Ontario, Canada, when PPV was first discovered in 2000, the low incidence but widely dispersed epidemic extended throughout the stone fruit industry. The Canadian programme was initially predicated on vigilant surveys plus PPV-infected tree and block removal to reduce PPV incidence, followed by increasingly stringent eradication protocols over time. However, eradication was not achieved prior to programme termination in 2011. Retrospective analyses of the Canadian epidemic indicated that the estimated PPV distribution from known sources followed a pulse-peak-decay function. The function indicated that viruliferous aphids transmitted infections most commonly at 43 m (peak) distance from prior infections, but PPV distribution also has a long (decaying) tail. A Weibull model, fitted to the proportion of new PPV-infected trees detected, demonstrated that 95% of new infections occurred within 628 m, 465 m and 317 m distances, for 1, 2 and 3-yr moving averages, respectively. Results suggest that eradication might be achievable by employing a 317–628 m cull radius distance. The discontinuation of the PPV eradication programme in Ontario will result in an increase of PPV in the region, if no spread prevention measures are implemented, and threaten the nearby New York State stone fruit industry. A risk-based survey methodology for commercial and residential stone fruits has been developed to sample Prunus orchards throughout New York that emphasizes proximity to prior PPV discoveries, and proximity to the Canadian border.}, number={4}, journal={CANADIAN JOURNAL OF PLANT PATHOLOGY}, author={Gottwald, Tim R. and Wierenga, Eric and Luo, Weiqi and Parnell, Stephen}, year={2013}, month={Oct}, pages={442–457} }