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This approach to controlling citrus greening, by blocking bacterial transmission by the psyllid, runs contrary to existing ‘kill the insect’ strategies.

Logan Hawkes | Mar 04, 2017

Since the introduction of Huánglóngbìng (HLB–yellow dragon disease–or better known as citrus greening disease) reared its ugly head on U.S. soil in a Florida citrus grove in 2005, the disease has been a major threat to commercial citrus production across the country.

Before arriving in North America, HLB had already carved a path of destruction across the Far East, Africa, the Indian subcontinent and the Arabian Peninsula, and was discovered in July 2004 in Brazil. In its wake it left citrus growers around the world astounded at the inevitable and long-lasting risks the disease poses to global citrus industry.

During the first couple of years after reaching Florida, the disease had destroyed a huge section of the state’s successful citrus industry, and by 2009, just five years after its introduction in the region, almost every county within Florida had confirmed HLB cases among both commercial and private citrus groves. From there the disease spread

to adjoining states, eventually reaching citrus growing areas in Texas and finally as far west as California.The fight against HLB and the tiny psyllids that carry the bacteria from tree to tree is about as old as the disease itself. Recognizing the disease had the ability to threaten the global citrus industry, researchers from around the world began working on possible solutions to combat the spread of this dangerous citrus killer.

In spite of early efforts however, the tell-tale signs of the disease kept spreading.

 The early symptoms of HLB include leaves with yellowing veins appear along with asymmetrical chlorosis referred to as “blotchy mottle.” These are the most diagnostic symptoms of the disease, especially on sweet orange. Growers, ever fearful the disease would reach their trees, have been on constant lookout for leaves that are slow to develop and often with a variety of chlorotic patterns that often resemble mineral deficiencies such as those of zinc, iron, and manganese.

Regardless of treatment efforts, once established in a grove, the end result of the disease is proving to be inevitable, the complete decay and destruction of all infected trees.

Detection of the disease is one of the first hurdles facing citrus growers in modern times. When it comes to fighting HLB, growers face a number of unique challenges. For one, HLB-infected citrus trees do not show symptoms during the first year of infection, so there is a long period of time when a grower cannot visually detect an infected tree. But that hasn’t stemmed research efforts.

The spreading pandemic of the disease served to rally the global citrus industry and the many researchers who support it. Soon new and innovative treatments were being tested. In addition to antibacterial management and control and management of the psyllids that carry the disease, tree removal became a standard procedure to help curtail the rapid spread of the bacterium.

Soon, beneficial parasitoids were introduced and widely used to help control psyllid populations. Heat treatments in nurseries and on field trees covered by plastic wrap offered some slowing of the disease process in early research efforts. Hundreds of millions of dollars were being spent worldwide searching for a cure to the disease. A zinc-based bactericidal spray seemed to offer some hope.

Before long, breeders were offering new citrus varieties that were proving resistant to the bacterium that causes HLB. Bio-engineers have been devising methods to make citrus trees less attractive to the psyllids that carry the disease. But in recent months a new idea has surfaced, and while no one is ringing the bell of victory, researchers on the project are quietly voicing new hope in the war against the disease.

HOW IT WORKS

According to researchers, the reproductive and feeding habits of the psyllid make it the perfect carrier of the bacterium. An infected psyllid creates a localized infection when it feeds and transmits the bacterium into a citrus tree. It does not take long for the bacterium to spread throughout the plant, but the inoculum is first concentrated in the leaves and stems where the infected psyllid feeds. Female psyllids lay eggs in the same region where they feed. If these females are infected, their nymphs, which begin feeding in the infected area of the tree when they hatch, eventually acquire the bacterium, molt to the winged adult stage and disperse taking it along with them.

So researchers at the Boyce Thompson Institute, a premier life sciences research institution located in Ithaca, New York on the Cornell University campus, have concentrated their recent efforts on the psyllid itself as a possible link to the control of the disease.

Michelle Cilia, a Research Molecular Biologist at the USDA Agricultural Research Service and Assistant Professor at the Boyce Thompson Institute (BTI), and her team of researchers have been looking at a protein that makes the bellies of citrus psyllids blue and the possible connection it may have with the natural process of spreading the devastating bacterium in the first place. Researchers say Asian citrus psyllids with blue abdomens have high levels of an oxygen-transporting protein called hemocyanin.

According to Cilia, the hemocyanin protein is commonly found in the blood of crustaceans and mollusks. When harboring the bacterium Candidatus Liberibacter asiaticus ( or CLas) the disease is spread by the Asian citrus psyllid. This bacterium force the psyllids to ramp up their production of this protein. Cilia lab scientists, along with colleagues at the University of Washington and the USDA ARS at Fort Pierce, Fla., identified important protein interactions that must occur to perpetuate the transmission of bacterium to new trees.

They examined interactions occurring between the psyllid and the bacterium, and between the psyllid and its beneficial microbial partners. They also compared protein expression levels in both nymphs and adults. Their research shows that adult psyllids appear to mount a better immune response to CLas as compared to nymphs, which may explain why psyllids must acquire CLas during the nymphal stage to efficiently transmit CLas once they become adults.

“For many decades, scientists lacked the ability to look inside insects that transmit plant pathogens and understand what is going on,” said Cilia. “This is no longer true today, thanks to the painstaking work of our collaborators in the Bruce and MacCoss labs at the University of Washington. The new molecular tools developed by our University of Washington colleagues enable us to dissect the vector-pathogen relationship piece by piece to determine which components are important for transmission.”

The group showed that hemocyanin interacts with a CLas protein involved in a vital microbial metabolic pathway called the acetyl-CoA pathway. Scientists have previously targeted this set of biochemical reactions in bacteria when developing antibiotics.

John Ramsey, a USDA ARS postdoctoral associate in the Cilia lab and first author of the study, suspects that the increase in hemocyanin, and the blue color it imparts to the abdomen, could be evidence of an immune response to CLas infection. The findings raise the possibility that this response could be harnessed to help control the bacterium’s spread.

“The study is allowing you to look at your population of insects and say something about the immune system of the insect based on its color,” said Ramsey. “There’s the possibility that this could be a useful part of grove surveillance.”

In future work, the Cilia group plans to test whether there are differences in each color morph’s ability to spread the CLas bacterium. Results from this study will help inform future strategies to control citrus greening disease. Depending on which proteins they decide to target, these new approaches could prevent the psyllid from transmitting CLas or trigger an immune response against the bacterium.

This approach to controlling citrus greening, by blocking bacterial transmission by the psyllid, runs contrary to existing ‘kill the insect’ strategies, said Ramsey. Such an approach may provide a longer lasting solution because the insect isn’t under pressure to evolve to survive the treatment, which commonly occurs with pesticide usage.

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In this video, scientists and local people explain the dangers of Opuntia stricta,  an invasive cactus weed covering large tracts of land in Kenya’s semi-arid Laikipia County, and efforts in place to tame its spread and adverse impacts.

O. stricta, a native plant of South America, is causing problems for people, domestic animals as well as wildlife. It was introduced in Kenya as an ornamental plant but has since invaded community lands according to Arne Witt, regional coordinator for invasive species at the Center for Agriculture and Biosciences International (CABI).

In Laikipia, about 253 kilometres to the north of Nairobi, Kenya’s capital city, it is dominating thousands of hectares of land given its fast propagating nature. As a result it is reducing the area of agricultural farmlands, wildlife areas and ranches. It is also causing socioeconomic and health challenges.

But scientists are now using a bio-control method in the area to destroy the weed. They have introduced a sap-sucking bug called Dactylopius opuntiae, commonly known as cochineal. It was imported from South Africa where it is being used to control the cactus weed in Kruger National Park.

Bio-control is restoring the ecosystem’s natural balance and curbing the weed’s spread, Witt explains. The cochineal specifically feeds on the cactus and has gone through laboratory tests to ensure it has no non-target impacts, especially on other plants.

Since the introduction of cochineal in the Laikipia areas of II Polei, Naibunga and Dol Dol, infected plants have virtually stopped producing fruit, inhibiting further spread of this noxious weed. This is more so where communities have embraced the use of cochineal, according to Witt.

O. stricta cannot be suppressed through chemical and mechanical control because of the costs associated with those methods. The spread of the cactus in Laikipia, Witt explains, is fuelled by the fact that it adapts well to semi-arid regions.

He says bio-control is a long-term, sustainable and effective way of controlling widespread invasive species in Africa.  “Embracing bio-control in Africa, not only for controlling invasive plants but also for controlling crop pests is crucial as pests become resistant to chemicals over time,” says Witt. “Over 200 weeds species [are] resistant to herbicides, 500 weed species are resistant to chemicals.”

A survey has shown that O. stricta spread is getting worse, but Witt is optimistic that in four to five years cochineal will get established.

Invasive species is a growing concern in Kenya — 50 per cent of such plants are introduced intentionally into the country for ornamental or agro-forestry purposes.

“Invasive species [are] foreign species brought from somewhere else as a result of human activities, and once established in a new environment, their proliferation starts to have a negative impact on diversity, crop production and animal health,’’ Witt says.

He adds, “We need a strict surveillance in place such that any new invasive [species] can be detected very early and eradicated.”

Kimani Kuria, manager of the community development programme at Ol Jogi Game Reserve, says science is playing a big role in biological control. “When harvested, the plants stay in the green house for two months laced with cochineal”, he says, adding that using the green house is improves the control and speed of the process.

The impact of O. stricta extends to wildlife and livestock. When abandoned baby elephants are rescued, Kuria explains, their tongues are found to be septic as a result of damage from the plant, and they cannot feed well. He says this is also seen in livestock in neighbouring communities, as the majority depend on livestock production. “If we do not manage Opuntia stricta, we will lose millions of dollars in range land production and livestock production in Kenya.’’

Kuria explains that the cactus has a waxy layer on the leaves, which means that a high concentration of chemical or other methods are required to control it, which would pose a threat to non-target organisms.

This multimedia piece is part of a series on invasive species supported by CABI

This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk

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Originally posted on CABI Invasives Blog: Copyright: Panos It is the end of December 2016, with clear skies over Niger. But as 2017 draws near prospects are grim for some 500 residents in Bani Kosseye, a village 80km from the capital Niamey. Agricultural production has been poor here, and families’ meagre stocks are expected to run…

via The locust invasions devastating Niger — The Plantwise Blog

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Tuta absoluta Meyrick

Generic News Alert Iconhttp://www.pestalert.org/viewNewsAlert.cfm?naid=91

Tuta absoluta (Tomato leaf miner): New host records, controls, and distribution

IDENTITY

Name: Tuta absoluta Meyrick

Taxonomic Position:

Animalia : Arthopoda : Insecta : Lepidoptera : GelechiidaeCommon Names:

Tomato leaf miner

Significance:

Tuta absoluta has been highlighted in previous NAPPO-PAS Pest Alerts (http://www.pestalert.org/viewNewsAlert.cfm?naid=78&keyword=tuta%20absoluta, http://www.pestalert.org/viewNewsAlert.cfm?naid=57&keyword=tuta%20absoluta). It is a significant pest of Solanum lycopersicum (tomato) and other economically important solanaceous plants, such as Solanum tuberosum (potato) and Capsicum annuum (pepper), and has also been found on Phaseolus vulgaris (bean).
Issues of Concern:
A recent publication reports that, during a 2009 to 2011 survey, Tuta absoluta was found infesting Beta vulgaris (beet), Chenopodium bonus-henricus (good King Henry), C. rubrum (red goosefoot), and Spinacia oleracea (spinach) plants in Algeria (Drouai et al., 2016). This is the first report of these plant species as hosts of T. absoluta.

Control of Tuta absoluta is mainly through chemical means, but the larvae feed internally and quickly can develop resistance. During a 2010 to 2014 study in Italy and Greece, Tuta absoluta exhibited resistance to the diamide insecticides chlorantraniliprole and flubendiamide, which is the first report of T. absoluta resistance to this type of insecticide. High resistance levels (>1,000-fold) were detected in Italy, and low but increasing resistance levels (>10-fold) were detected in Greece (Roditakis et al., 2015). Some biological controls are available, such as the mirid bugs Nesidiocoris tenuis and Macrolophus pygmaeus (De Backer et al., 2014), and another publication reported that the assassin bug Zelus obscuridorsis (Hemiptera: Reduviidae) was observed on tomato plants infested with T. absoluta in household gardens in Argentina during 2012 surveys. Laboratory tests indicated that Z. obscuridorsis feeds on mobile larvae and adults of T. absoluta, but not on larvae within leaf mines, eggs, or pupae, which is the first report of a Zelus species feeding on T. absoluta (Speranza et al., 2015).
Distribution:
Tuta absoluta is native to South America and has been widely reported from parts of Central America, Europe, Africa, and the Middle East (CABI, 2016). Most recently, T. absoluta has been collected from pheromone traps in Zambia (IPPC, 2016a), South Africa (IPPC, 2016b) and Mozambique (IPPC, 2017), and there has been first reports from Nigeria (Aishat, 2016), Uganda (Tumuhaise et al., 2016), India (ICAR, 2015), Nepal (Bajracharya et al., 2016), Bangladesh (Hossain et al., 2016), and Botswana (Tebele, 2017). It is not known to occur in the United States, Canada, or Mexico.

References:

Aishat, O. 2016. Brief on tomato fruits scarcity in Nigeria. Federal Ministry of Agriculture and Rural Development (Nigeria). May 25, 2016

Bajracharya, A. S. R., R. P. Mainali, B. Bhat, S. Bista, P. R. Shashank, and N. M. Meshram. 2016. The first record of South American tomato leaf miner, Tuta absoluta (Meyrick 1917) (Lepidoptera: Gelechiidae) in Nepal. Journal of Entomology and Zoology Studies 4(4):1359-1363.

CABI, 2016. Tuta absoluta. In: Invasive Species Compendium. Wallingford, UK: CAB International. http://www.cabi.org/isc.

De Backer, L., Megido, R. C., Haubruge, É., and Verheggen, F. J. 2014. Macrolophus pygmaeus (Rambur) as an efficient predator of the tomato leafminer Tuta absoluta (Meyrick) in Europe. A review/Macrolophus pygmaeus (Rambur), prédateur efficace de la mineuse de la tomate Tuta absoluta (Meyrick) en Europe (synthèse bibliographique). Biotechnologie, Agronomie, Société et Environnement, 18(4): 536.

Drouai, H., F. Mimeche, A. Zedam, H. Mimeche, M. Belhamra, and M. Biche. 2016. New floristic records of Tuta absoluta Meyrick 1917, in Zibans’s Oasis (Biskra Algeria). Journal of Entomology and Zoology Studies 4(6):130-132.

Hossain, M. S., M. Y. Mian, and R. Muniappan. 2016. The first record of Tuta absoluta (Lepidoptera: Gelechiidae) in Bangladesh. Journal of Agricultural and Urban Entomology 32(1):101-105.

ICAR. 2015. Tuta absoluta: A new invasive pest alert. Indian Council of Agricultural Research (ICAR). February 17, 2015.

IPPC. 2016a. Reporting pest presence: Preliminary surveillance reports on Tuta absoluta in Zambia. International Plant Protection Convention (IPPC). September 14, 2016.

IPPC. 2016b. First detection of Tuta absoluta in South Africa. International Plant Protection Convention (IPPC). September 1, 2016.

IPPC. 2017. Occurrence of tomato leaf miner (Tuta absoluta) in Mozambique. International Plant Protection Convention (IPPC). January 13, 2017. Last accessed January 26, 2017, from https://www.ippc.int/en/countries/mozambique/pestreports/2017/01/occurrence-of-tomato-leaf-miner-tuta-absoluta-in-mozambique/.

Roditakis, E., E. Vasakis, M. Grispou, M. Stavrakaki, R. Nauen, M. Gravouil, and A. Bassi. 2015. First report of Tuta absoluta resistance to diamide insecticides. Journal of Pest Science 88(1):9-16.

Speranza S., M. C. Melo, M. G. Luna, and E. G. Virla. 2014. First record of Zelus obscuridorsis (Hemiptera: Reduviidae) as a predator of the South American tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae). Florida Entomologist 97(1):295-297.

Tebele, M. 2017. SADC tomato production under threat. The Southern Times. January 23, 2017. Last accessed January 26, 2017, from https://southernafrican.news/2017/01/23/sadc-tomato-production-under-threat/.

Tumuhaise, V., F. M. Khamis, A. Agona, G. Sseruwu, and S. A. Mohamed. 2016. First record of Tuta absoluta (Lepidoptera: Gelechiidae) in Uganda. International Journal of Tropical Insect Science 36(3):135-139.
Warning: The information in this alert has not been confirmed with the appropriate National Plant Protection Organization and is provided solely as an early warning. Please use the above information with caution.


Phytosanitary Alert System
Pest Alert http://www.pestalert.org
Prepared on: 02/01/2017

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New pest puts banana farmers on alert

By Express News Service  |   Published: 08th February 2017 01:31 AM  |

Last Updated: 08th February 2017 06:12 AM  |   A+A-   |  

Image for representational purpose only. | express

THIRUVANANTHAPURAM: A new variety of pest is found to be plaguing coconut and banana in the state, the Agriculture Department warned farmers on Tuesday.
The Rugose Spiralling Whitefly (Aleurodicus rugioperculatus) deposits its eggs on the underside of the leaves of coconut and banana and damages the crop. The droppings of the fly also cause damage to the leaves, resulting in less productivity from the crop. The pest was identified by P Raghunath of the College of Agriculture, Vellayani. This species of whitefly is endemic to Florida.

He urged coconut and banana farmers to be vigilant and take comprehensive precautionary measures. Leaves on which the pest attack is severe should be cut and destroyed. However, agriculture officials warned farmers against using any form of chemicals even on nearby crops. A blend of soap solution with neem oil and garlic extraction should be sprayed on the underside of the leaves. If the pest attack continues, farmers should spray a diluted solution of the KAU product verticilium.
Growing tulsi, pudina as intercrops also will help destroy the pests, the department said.

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UF/IFAS Extension

University of Florida

The Peanut Burrower Bug – an Emerging Pest in Peanuts

Xavier Martini, David Wright, UF/IFAS North Florida Research and Education Center

Burrower bugs are small Heteroptera insects with piercing/sucking mouthparts (Figure 1). There are six different species of burrower bugs that have been found to feed on peanuts. Among them, three are found in Georgia and Florida, but most of the damage has been attributed to the peanut burrower bug Pangaeus bilineatus. This species is native to Georgia, but can be found as far north as Connecticut. This species can survive up north despite the absence of peanuts, because it feeds on other plants such as cotton, peppers, strawberry, spinach, oak, peach, or pear.

Adults become active in the spring and lay eggs in the soil, while nymph activity is reported as early as mid-May. Burrower bugs spend most of their life cycle underneath the soil, feeding on mature peanut kernels and pods. Adults and nymphs feed directly on the peanut seed during the mid to late pod-fill by piercing the pods with their specialized mouth-parts.

peanut-1-slide2-e1487099699876

Despite the fact that damage on peanuts has been described for decades, it is only recently that burrower bug has become a recurrent problem in peanut crops in Georgia, Alabama, and Florida. The peanut burrower bug damages peanut kernels directly by feeding on them. The insertion of its mouth-part in the maturing kernel produces yellow feeding spots called “pitting” (Figure 2). Additionally, the peanut burrowing bug also affects peanut quality due to an increase of peroxide levels, and a rise in aflatoxin contamination. As peanuts grown in the USA are graded according to kernel internal damage, even a slight percentage of burrower bug damage might be detrimental for growers. With more than 2.5% of kernels showing internal damage, peanut grade drops to segment 2, and the value of the peanut load is dramatically reduced.

peanut-2-slide1

Burrower bug infestations and damage are highly variable from year to year. It is known that hot and dry conditions increase risk of burrower bug damage. As recent spring and summer weather patterns have tended to be hotter and drier, due to climatic phases, it may explain why this bug has become a recurrent pest in peanut production in the last several years. Also, tillage protocols have shown to effect burrower bug population, with reduced tillage practices being associated with increased burrower bug densities. Additionally, the choice of winter cover crop affects burrower bug populations. Peanuts tilled into corn or wheat residues have greater burrower bug populations and higher feeding damage than peanuts tilled into rye residues.

Burrower bugs can be sampled either by the use of pitfall traps or light traps during spring and summer. The main control methods for this pest is the application of granular chlorpyrifos at planting or at pegging.  However, the EPA is currently moving forward to potentially revoke all food residue tolerances for chlorpyrifos. Therefore, it is possible that, in the very near future, growers will have to turn to other insecticides such as bifenthrin, imidacloprid or lambda-cyhalothrin. However, the efficiency of these insecticides on burrowing bugs needs to be fully evaluated. Regarding biological control, the entomopathogenic nematode Heterorhabditis bacteriophora has been described as a potential control agent. Cultural methods to reduced burrower bugs populations include irrigation, as this bug prefers dry conditions. Conventional tillage can also reducing burrower bug population, however, this has to be counterbalanced with the benefits of conservation tillage that include the improvement of soil tilth, the increase of organic matter, the reduction of water evaporation, and the reduction of soil erosion.

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Scientific Modeling Helps Defend Tomatoes Against Flying Foe

January 31, 2017
IPM Innovation Lab Director Muni Muniappan inspects tomatoes damaged by Tuta absoluta in Puranchaur, Nepal. The pest was first reported in the country in spring of 2016, and it is already promising to be a big problem for the upcoming tomato-growing season.

Tomatoes are so abundant that they can be easy to take for granted. But a pest known as the South American tomato leafminer, or Tuta absoluta, has been making this popular ingredient harder to find in countries throughout the world. The tomato leafminer hasn’t arrived in the United States yet, but it has made it as far north as Costa Rica. Now, most scientists agree, it’s no longer a question of if this pest will arrive, but when.

“People want to know when Tuta will be in the United States,” said Muni Muniappan, director of the Feed the Future Innovation Lab for Integrated Pest Management, led by Virginia Tech University. “It could be in 1 year or 10 years, but eventually it will be here.”

Fresh and processed tomatoes generated $2 billion dollars in the United States in 2015 and tomato exports totaled $335 million, making America the seventh largest tomato-producing country in the world. An invasion by the tomato leafminer could put a serious dent in those numbers.

Muniappan and the Integrated Pest Management Innovation Lab have been working to combat the pest since it hitched a ride to Spain in 2006, where it then spread through Europe and the Mediterranean and into Central and South Asia and parts of Africa.

“There is no silver bullet for Tuta absoluta,” Muniappan said. “We cannot stop it, but we can slow it down.”

Under these circumstances, the best way to protect countries that have not been reached by the pest is to delay its arrival and increase awareness about it. Then, if it does arrive, the key is to limit its damage with a quick response.

To keep the pest out of America for as long as possible, the Integrated Pest Management Innovation Lab is helping monitor Tuta absouta and assist states in using pheromone traps for early detection. It is also working with Costa Rica to suppress the pest and prevent its northward spread.

When the pest does inevitably enter the United States, quarantine measures will be necessary. To this end, the Integrated Pest Management Innovation Lab recently gave funding to Virginia Tech’s Biocomplexity Institute to model the spread of Tuta absoluta, using human movement as a variable. Most models use only temperature and weather patterns as predictors of disease and pest spread, but the model developed through this project will also consider popular trade and travel routes.

“Our model will be an extremely useful tool to develop strategies to combat these pests,” said Abhijin Adiga, a research faculty member at the Biocomplexity Institute and project lead. “Further, the methodology will not be limited to studying the tomato leafminer but can be applied to any agricultural invasive species.”

Muniappan and the Integrated Pest Management Innovation Lab are raising awareness in America and around the world about the pest. So far, they’ve held 16 international awareness workshops, reaching scientists from 55 countries. At the International Congress of Entomology in October 2016 in Florida, the Feed the Future Innovation Lab led a symposium, resulting in the group recommending several measures, such as undertaking a concentrated effort to look for natural enemies in Tuta’s area of origin in South America and providing information on appropriate insecticide rotations for pest management in the fields.

“With proactive actions,” Muniappan said, “we hope to significantly reduce the economic loss caused by this pest in the United States and around the world.”

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