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Contribute to CABI’s new Plant Health Cases

Real-life examples of plant health in practice. 

About Plant Health Cases

Fresh green soy plants on the field in spring. Rows of young soybean plants . High quality photo

CABI, together with Editors in Chief Lone Buchwaldt, David B. Collinge, and Boyd A. Mori is embarking on a new type of online publication called Plant Health Cases.

Plant Health Cases will be a curated, peer-reviewed collection of real-life examples of plant health in practice. This will be an invaluable resource for students, lecturers, researchers, and research-led practitioners. We will be developing cases in all areas relevant to plant health, including:

  • plant diseases
  • plants pests
  • weeds
  • environmental factors
  • agronomic practices
  • diagnosis, prevention, monitoring and control
  • international trade and travel

What is a Case Study?

A Plant Health Case is a relatively short publication with a well-defined example of research in plant health, e.g. a study which results in reduced impact from a disease or pest problem. Cases should be between 3000 and 5000 words long, and can include photos, figures and tables. They should be written in an engaging style that is both science-based and accessible using a limited number of references. Importantly, each case should suggest points for discussion to broaden the reader’s horizon, inspire critical thinking and lead to interactions in the classroom or field.

Interested in Contributing to Plant Health Cases?

We are currently looking for contributions of case studies, and we welcome your ideas! You may have existing case study material ready prepared for use in teaching, or a good example of research in plant health which could be easily adapted to our template. For further information and guidance on how to submit your idea for a case study please see here: https://www.cabi.org/products-and-services/plant-health-cases/

Your submission will be peer-reviewed, and a DOI assigned at the time of publication similar to your other scientific publications. The corresponding author will receive £100 upon acceptance of the final case study. 

Publication Plan

We’re aiming to launch Plant Health Cases in mid-2023. Our case studies will offer practical, real-life examples in one easily searchable platform. All users will be able to search, browse and read summaries of case studies. Full text access will be available via individual or institutional subscription, or by purchasing a single case study.

Further Information

Please get in touch with Rebecca Stubbs, Commissioning Editor, CABI

r.stubbs@cabi.org

About CABI

CABI is a not-for-profit, scientific research, international development and publishing organisation. Unlike other publishers, we use our surpluses to support scientific and rural development projects that help improve the lives of the world’s poorest people, which means that by publishing with us, you are helping to improve the lives of some of the world’s poorest people. Please visit our website at www.cabi.org


SEPTEMBER 14, 2022

Can wild potato relatives help tame zebra chip disease?

by Paul Schattenberg, Texas A&M University

Can wild potato relatives help tame zebra chip disease?
Kranthi Mandadi, Ph.D, a Texas A&M AgriLife Research scientist at the Texas A&M AgriLife Research and Extension Center in Weslaco, was the primary investigator for the new zebra chip-related study. Credit: Texas A&M AgriLife photo

A new study led by Texas A&M AgriLife researchers has revealed some resistance to zebra chip disease among certain wild species of potato.

The study of 52 wild potato species—of which one accession was resistant and three were tolerant to the disease—took place as part of an effort to identify novel genetic resistance to the disease, which affects potato production worldwide.

The study, “Identification and Characterization of Potato Zebra Chip Resistance Among Wild Solanum Species,” appeared recently in the journal Frontiers in Microbiology.

The primary investigator for the study was Kranthi Mandadi, Ph.D., a Texas A&M AgriLife Research scientist at the Texas A&M AgriLife Research and Extension Center at Weslaco and associate professor in Texas A&M’s Department of Plant Pathology and Microbiology.

Study co-investigators include Isabel Vales, Ph.D., AgriLife Research associate professor and potato breeder, Bryan-College Station, and Carlos Avila, Ph.D., AgriLife Research associate professor and vegetable breeder, Weslaco, both in the Department of Horticultural Sciences; and Freddy Ibanez, Ph.D., an AgriLife Research scientist at the center and assistant professor in the Texas A&M Department of Entomology.

Others involved in the study were Texas A&M AgriLife Research scientists Victoria Mora, M.S., Manikandan Ramasamy, Ph.D., Mona Damaj, Ph.D., and Sonia Irigoyen, Ph.D., at the Weslaco center, as well as Veronica Ancona, Ph.D., a plant pathologist and associate professor at Texas A&M University-Kingsville.

“This type of outcome was precisely what AgriLife Research envisioned when we decided to fund Insect Vector Diseases Seed Grants,” said Henry Fadamiro, Ph.D., chief scientific officer and associate director, AgriLife Research, and associate dean, Texas A&M College of Agriculture and Life Sciences. “We would like to thank the Texas Legislature for funding AgriLife Research’s IVD Exceptional Item Request that has made these seed grants possible. Their continued support is invaluable.”

What is zebra chip disease?

Zebra chip is a complex disease due to its association with the unculturable bacteria Candidatus Liberibacter solanacearum and transmission by an insect vector, the potato psyllid. First reported in Saltillo, Mexico, and subsequently in South Texas, the disease was detected in many other states and commercial potato-growing regions of the world. Left unchecked, it can result in potato yield losses of up to 94%.

Can wild potato relatives help tame zebra chip disease?
Potato tubers affected by zebra chip disease are of poor quality, have a bitter taste and display dark brown zebra-like patterns when fried. Credit: Texas A&M AgriLife photo

Above-ground symptoms of zebra chip-affected plants include purplish discoloration of young leaves, upward rolling of top leaves, the presence of aerial tubers, wilting, stunted growth and plant death.

“Zebra chip-affected tubers are of poor quality, exhibiting vascular ring browning and brown flecks,” Mandadi said. “These chips also have a bitter taste and dark brown striped, zebra-like patterns when fried.”

He said the disease ultimately lowers yield and tuber quality becomes unmarketable.

“If left uncontrolled, the disease can become a significant detriment to potato production.”

Why the study?

The potato is cultivated in over 160 countries and is considered the fourth most important staple food crop after wheat, corn and rice. It is a rich source of carbohydrates and provides other essential nutrients, such as dietary fiber, vitamins, minerals, protein and antioxidants.

“The potato is an important food crop worldwide,” Mandadi said. “As the demand for fresh and processed potato products increases globally, there is a need to manage and control emerging diseases such as zebra chip.”

In Texas, potatoes are grown in all regions that have a significant amount of commercial vegetable production. Commercial acreage for potato production is found in the South Plains, Panhandle and Rolling Plains, as well as the Winter Garden and Rio Grande Valley areas.

“In Texas, we have been dealing with the zebra chip issues for more than 20 years,” Vales said. “Over that time, the disease has become pervasive and has expanded not only in this state but also in other potato-producing states.”

Can wild potato relatives help tame zebra chip disease?
The Texas A&M AgriLife-led study involved the assessment of plant material from 52 wild potato accessions. Credit: Texas A&M AgriLife photo by Kranthi Mandadi

The bacterium and the insect vector associated with zebra chip disease can also affect other vegetable crops and produce, including tomatoes, peppers and carrots.

Vales said current zebra chip management strategies revolve primarily around controlling the psyllid vector with insecticides or by altering cultural practices, such as timing planting dates to delay exposure to the psyllid population.

“But both of these have only marginal benefits, and while using chemical measures has helped control the psyllid population, this approach is associated with high costs and the potential for increased insecticide resistance,” she said. “That’s why identifying and breeding novel genetic resistance and tolerance to the zebra chip is another important avenue to achieve integrated pest management.”

Vales said previous studies have reported variations in the psyllid’s preference for wild potato species and their breeding clones.

The study results

“For the past four years, our team has been studying approaches to control zebra chip disease thanks to seed funding from projects associated with the Insect Vector Diseases Grant Program,” Mandadi said.

The plant material of 52 wild potato accessions belonging to a Solanum sect. Petota diversity panel, grown from true potato seeds obtained from the U.S. National Plant Germplasm System in Wisconsin, was used in the study.

“New sources of zebra chip resistance were identified among a wild collection of tuber-bearing Solanum species present in the Petota panel,” Mandadi said. “This panel of wild potato is a taxonomically well-characterized and diverse collection from which one can mine for valuable potato traits.”

Several of the 52 accessions were susceptible and moderately susceptible, showing some upward leaf rolling, chlorosis and plant stunting, Mandadi said.

Can wild potato relatives help tame zebra chip disease?
According to the study, the S. berthautii wild potato accession, shown here, demonstrated zebra chip psyllid resistance. Credit: Texas A&M AgriLife photo by Kranthi Mandadi

“But following the screening, phenotypic evaluations and quantification of the bacteria in the accessions infected with bacteria-carrying psyllids, we identified one zebra chip resistant accession, Solanum berthaultii, along with three other accessions that were moderately tolerant to zebra chip.”

The three accessions identified in the study as moderately tolerant to zebra chip were S. kurtzianum, S. okadae and S. raphanifolium.

Mandadi’s team also found S. berthaultii has dense glandular leaf trichomes, and this foliar structural modification could be one factor responsible for much of the observed zebra chip resistance.

“The foliar portion produces a sticky substance that seems to trap the psyllid to the plant when it comes in contact with it,” Mandadi explained. “As a result, many psyllids die before reproducing, thus reducing transmission of the bacterium into plants.”

He noted the S. berthautii wild potato accession originated in Bolivia, which is adjacent to Peru, historically identified as the ancestral “birthplace” of the cultivated potato.

He said S. berthaultii is a promising source for zebra chip psyllid resistance that can be further studied to understand insect resistance mechanisms and incorporated into the potato production system.

“It could possibly be used in breeding new potato cultivars or even as a ‘trap crop’ that can be planted next to more traditional potato cultivars as a way to help eliminate psyllids,” Mandadi said.

He also noted that similar approaches in identifying novel genetic resistance and tolerance in wild plant species could help control other devastating crop diseases, such as potato late blight, citrus greening, Pierce’s disease of grapes and banana wilt.


Explore further

New variety of zebra chip disease threatens potato production in southwestern Oregon


More information: Victoria Mora et al, Identification and Characterization of Potato Zebra Chip Resistance Among Wild Solanum Species, Frontiers in Microbiology (2022). DOI: 10.3389/fmicb.2022.857493

Provided by Texas A&M University 

  Grahame Jackson

PestNet

 Sydney NSW, Australia

 For your information

 8 days ago

Soybean virus may give plant-munching bugs a boost in survival

PennState

UNIVERSITY PARK, Pa. — Most viral infections negatively affect an organism’s health, but one plant virus in particular — soybean vein necrosis orthotospovirus, often referred to as SVNV — may actually benefit a type of insect that commonly feeds on soybean plants and can transmit the virus to the plant, causing disease, according to Penn State research.

In a laboratory study, the Penn State College of Agricultural Sciences researchers found that when soybean thrips — small insects ranging from 0.03 to 0.20 inches long — were infected with SVNV, they tended to survive longer and reproduce better than thrips that were not infected.

Asifa Hameed, who led the study while completing her doctoral degree in entomology at Penn State and is now a senior scientist of entomology at Ayub Agricultural Research Institute in Multan, Pakistan, said the findings give key insight into how the virus spreads in plants and affects its insect hosts.

“In addition to prolonging the life of the insects, SVNV infection also shortened the doubling time of soybean thrip populations,” Hameed said. 

 Soybean_vein_necrosis_orthotospovirus

  International Plant Health Conference  21 – 23 September 2022 | 09:00-18:00 Queen Elizabeth II Centre | London UK     Dear plant health colleagues and friends,   Plant health is a key factor in any strategy to achieve food security, protect the environment and biodiversity, and facilitate safe trade.   In the past months, the Secretariat of the International Plant Protection Convention has been working closely with the Department for Environment, Food & Rural Affairs (DEFRA) of the United Kingdom (UK) and the Food and Agriculture Organisation (FAO) of the United Nations, on organizing the first-ever International Plant Health Conference (IPHC), being held in London, the UK, from 21 – 23 September.     The IPHC aims to address new and emerging plant health challenges, including climate change impacts, the rapid loss of biological diversity, the significant increase in international trade, and new pest pathways such as e-commerce.   The IPHC is a unique opportunity to raise global awareness and promote the importance of protecting plant health. Take part in the crucial discussions on plant health by following the Live webcast on the IPHC webpage.   Information on the IPHC and a collection of plant health resources (key messages, social media assets, publications, videos, stories, podcasts, and more) are available on the IPHC Trello board. Please don’t forget to tag IPPC (Facebook, Twitter) when posting on social media and remember to use the official event hashtag #PlantHealthConference.    I would be pleased to hear your thoughts and ideas on the way forward to promote plant health globally. Sincerely, Osama El-Lissy 
Secretary 
International Plant Protection Convention
Join the conversation on the #PlantHealthConference!

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UAF VC Urges Scientists To Discover New Biological Control For Parthenium

 Sumaira FH  Published September 09, 2022 | 07:48 PM

UAF VC urges scientists to discover new biological control for Parthenium

University of Agriculture Faisalabad (UAF) Vice Chancellor Prof Dr Iqrar Ahmad Khan has urged agricultural scientists to discover new biological control for Parthenium as it is spreading at an alarming rate across the country

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FAISALABAD, (UrduPoint / Pakistan Point News – 9th Sep, 2022 ) :University of Agriculture Faisalabad (UAF) Vice Chancellor Prof Dr Iqrar Ahmad Khan has urged agricultural scientists to discover new biological control for Parthenium as it is spreading at an alarming rate across the country.

He was addressing an international seminar on “Biological Control of Parthenium hysterophorus in Pakistan using stem boring weevil (Listronotus setosipennis)”, organised by the university in collaboration with the CABI Regional Bioscience Centre Pakistan.

He said that Parthenium was spreading rapidly both in rural and urban landscapes in the country after crossing continents. It was highly-invasive due to its prolific seed production, flower production within four weeks of germination, tolerance to varying climatic conditions, and the production of allelochemicals that affect the growth of nearby plants.

He said that agri scientists were duty bound accelerate their efforts for control Parthenium in addition to creating awareness among the farming community about destructive effects of this weed so that it could be controlled at maximum extent.

Dr. Philip Weyl, Weed Biocontrol Specialist from CABI Switzerland during his address said that Listronotus was a natural enemy of Parthenium, from the weed’s native range of Central America. Listronotus was a nocturnal weevil that layed its eggs primarily in the flowers of Parthenium where newly hatched larvae tunnel into the stem and continue to feed, eventually exiting at the base of the stem to pupate in the soil. Several larvae feeding in the stem can kill Parthenium rosettes and mature plants.

Pro-Vice Chancellor UAF Prof Dr Anas Sarwar Qureshi also addressed the seminar and called for innovative approaches to address the issues of the agricultural sector.

He said that excessive usage of chemicals on crops was creating health and environmental hazards. He said that adoption of latest scientific trends was need of the hour to cope with agricultural challenges at national level because this sector was directly linked to poverty alleviation.

Chairman Entomology UAF Prof Dr Sohail Ahmad highlighted the importance of research needed around the biocontrol of parthenium and other invasive weeds.

He said that the country faced the catastrophe due to heavy floods in which we had lost vast range of agriculture. The university had also mapped out a comprehensive plan to rehabilitate this sector in flood hit areas, he added.

Abdul Rehman from CABI said that keeping in view the destructive impacts of Parthenium weed, CABI initiated a biological control programme in Pakistan in 2017. For this purpose, CABI’s established a new quarantine laboratory at its Rawalpindi centre in Pakistan to enhance its capabilities to manage Parthenium weed.

The new quarantine facility allowed scientists to investigate a range of biological control options including the stem boring weevil Listronotus setosipennis.

Dr. Ijaz Ashraf from UAF shared updates on an awareness campaign for control of Parthenium hysterophorus in Pakistan and said that university students were on front foot to sensitize stakeholders and communities on negative impacts of Parthenium.

He vowed that such awareness-raising interventions around invasive species management and other agricultural challenges would be continued in close collaboration with CABI.

Global Agriculture 

New research maps potential global spread of devastating papaya mealybug pest

   Delhi Bureau  1 Comment Biopesticides & BiocontrolsCABI  4 min read

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10 November 2020, UK: CABI scientists have mapped the potential global spread of the devastating papaya mealybug (Paracoccus marginatus), highlighting new areas in Africa, Asia and the Americas into which this pest could potentially invade.

Also Read: BASF commits to targets for boosting sustainable agriculture

The papaya mealybug, which is native to Mexico and Central America, can have severe impacts upon livelihoods and food security. In Ghana, for example, infestations led to a 65% yield loss which reduced export earnings and resulted in the loss of 1,700 jobs.

Using location data received through collaborations with Kerala Agricultural University, India; the National Rice Research Institute, India; the Bangladesh Agricultural UniversityUniversity of Queensland, Australia; the International Institute of Tropical Agriculture (IITA); Fujan Agriculture and Forestry University in China and CSIRO, researchers were able to model the potential distribution of this pest, taking into account environmental conditions, and the distribution of suitable host crops and irrigation patterns.

The researchers, led by CABI’s Dr Elizabeth Finch, believe the polyphagous insect pest, which affects over 200 plants including economically important crops such as papaya, cassava and avocado, could spread to areas such as the south of the Democratic Republic of Congo, northern Cameroon, Zambia, Madagascar and western Ethiopia which are environmentally suitable and have suitable crop hosts.

In the Americas, the research, published in the journal Pest Management Science, suggests papaya mealybug could extend into El Salvador, Honduras, Nicaragua, and Panama – although the scientists believe it could already be in these locations but its presence is yet to be confirmed.

Whilst papaya mealybug is already present in Florida, where it is under successful control as a result of the release of endoparasitoid wasp species – Acerophagus papayaeAnagyrus loeckiAnagyrus californicus – suitable conditions for this pest are also present in the southern tip of Texas.

Conditions are likely to be too cold in the rest of the USA for permanent papaya mealybug populations, however the research showed that seasonal populations could survive in California, along the Pacific coastline and in the central and eastern states of the USA during the warmer summer months.

Also Read: FMC Corporation Recognized at 2020 Crop Science Awards

In Asia, the areas with suitable conditions were more expansive than the areas with known populations of papaya mealybug, suggesting the potential for further expansion of papaya mealybug specifically in India, Southeast Asia and the southern regions of the Guangxi and Guangdong provinces of southern China.

However, in Australasia the risk is low as only a small amount of fragmented land along the north-eastern side of Queensland, from the very northern tip of Queensland to Bundaberg, is climatically suitable. This is due to heat stress from the high temperatures on the continent.

Similarly, in Europe – though due to cold rather than heat stress – widespread distribution of papaya mealybug is not expected, with only a very small area of land surrounding Seville in Spain and around Sicily in Italy having suitable conditions for resident populations.

Dr Finch said, “This pest has been so successful due to its quick development and prolific reproductive capacity. It has the potential to spread to new areas and rapidly reach high numbers unless suitable phytosanitary or control methods are implemented.

“Information about the papaya mealybug’s potential distribution is important as it can highlight key areas susceptible to invasion, giving an early warning to decision makers, allowing them to put into place phytosanitary measures to prevent or slow the invasion of the pest into their jurisdiction.”

Dr Finch added, “In areas where the papaya mealybug has become established and reached a high enough population density, the use of parasitoids – such as Acerophagus papayae and Anagyrus loecki – remains an effective potential control method.

“Further ecological niche modelling of these parasitoid species is recommended to anticipate their survival, fitness and ultimate biological control impact in areas into which papaya mealybug could potentially expand and become established.”

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Biopesticides and Biocontrols 

Could biocontrol solve the papaya mealybug problem for Ugandan farmers?

   Delhi Bureau  0 Comments CABI  4 min read

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14 September 2022, Uganda: Papaya mealybug, Paraccous margniatus, is native to Central America but has spread rapidly in invaded countries. It was detected in Uganda in 2021 where it has the potential to affect the production and quality of papaya and other host crops.

Typically, mealybugs are not pest problems in the countries they are native to because naturally occurring parasitoids and predators keep their numbers in check. The most serious outbreaks occur when mealybugs are introduced accidentally to new countries without natural enemies.

Papaya mealybug spread

The trade in live plant material, such as papaya fruits and seedlings, has accidentally accelerated the spread of papaya mealybug outside its native range. This pest threatens food and nutrition security and adversely affects the safe trade and competitiveness of the agricultural sector for many countries.

Without natural enemies to manage outbreaks, farmers often turn to pesticides. The lack of registered pesticides results in farmers using highly hazardous chemicals that are not only ineffective but can negatively impact native insect biodiversity such as pollinators and natural enemies of pests. A more ecologically sound approach to management is the use of biological control.

Rapid Rural Appraisal of papaya mealybug

As part of the PlantwisePlus programme, CABI in collaboration with the National Agricultural Research Organisation (NARO, Uganda), conducted a Rapid Rural Appraisal (RRA) of papaya mealybug in Uganda. The appraisal sought to gain an understanding of the presence, distribution, and impact of papaya mealybug in Uganda as well as farmers’ management practices. The evaluation also assessed farmers’ willingness to adopt and use biocontrol and their information requirements around biocontrol products.

Information from the appraisal will be used to design an integrated management strategy for papaya mealybug as well as help target community-level communications.

A major cash crop

The seventeen focus group discussions brought together papaya growers from four districts: North District (Lira), Central District (Kayunga, Luwero and Mukono). The districts captured a diversity of farming systems, agro-ecological zones, and agricultural potential. Papaya is a major cash crop for farmers in these districts, in addition to pineapple and traditional cash crops such as coffee. The average farmer cultivates the crop on 0.75-2.5 acres.

The participants confirmed papaya mealybug is already widespread in all four districts where it causes damage to several crops, not just papaya. Farmers started observing the pest between 2017 and 2019 with most saying it is a serious pest that can cause up to 100% crop loss. The official pest reporting to IPPC took place in 2021.

Papaya mealybug management

Farmers mainly attributed the papaya mealybug outbreaks to low productivity and poor-quality fruits. They observed that trees take longer to bear fruit and when they do, they only last one season compared to an average of 4 before. It was estimated that before the pest invaded, farmers obtained UGX 6-8 million/acre each season (£1,800), but currently only obtain UGX 1 million/acre each season (£230).

Regarding management options, commercial farmers reported using pesticides to deal with outbreaks. However, managing papaya mealybugs with pesticides is not always successful due to the pest’s waxy covering. In addition, misuse and/or improper use of these pesticides exacerbate pest problems by reducing beneficial organisms and natural enemies and negatively impacting biodiversity, human health and environmental safety. Further, some farmers don’t observe pre-harvest intervals, thus toxic substances are likely to enter the human food chain posing long-term health risks to consumers and the environment.

Sustainable options

Biological control represents a sustainable and effective management option, however, the farmers interviewed had mixed views on the method and the efficacy of the parasitoid in Uganda’s agroecologies. This highlights the importance of proper testing and community-level communications before the introduction of exotic natural enemies. Farmer and community engagement, and mass awareness are key in pest identification and management, especially with the promotion of unfamiliar pest management options. Extension in particular plays a vital role in the research and advancement of low-risk options.

However, one of the main takeaways from the appraisal was farmers’ papaya problems extend beyond papaya mealybug. Farmers reported other associated viral and bacterial diseases causing challenges, including bunchy top disease and leaf necrosis. As such, it is important that researchers assess the economic damage, effect and losses due to papaya mealybug and the associated pests and diseases before releasing biological control parasitoids.

Implementing a biocontrol programme

The PlantwisePlus programme is now looking at the activities required for the implementation of the biocontrol programme in Uganda. In particular, they are developing extension and farmer training manuals to cover papaya crop integrated pest management. These will include papaya mealybug as well as other pests affecting papaya production in the country. In addition, continuous community engagement and mass awareness campaigns will help farmers and their communities manage this highly destructive pest in a more sustainable way. 

PlantwisePlus is working to reduce the reliance on high-risk farm inputs that have adverse effects on human health and biodiversity. By implementing biological control programmes, PlantwisePlus is responding to the challenge and working to improve livelihoods through sustainable approaches to crop production.

Also Read: Tractor sale in India lowest in two months; 32 percent down in August 2022

(For Latest Agriculture News & Updates, follow Krishak Jagat on Google News)

Could biocontrol solve the papaya mealybug problem for Ugandan farmers?

Papaya mealybugParaccous margniatus, is native to Central America but has spread rapidly in invaded countries. It was detected in Uganda in 2021 where it has the potential to affect the production and quality of papaya and other host crops.

Papaya
Papaya fruit

Typically, mealybugs are not pest problems in the countries they are native to because naturally occurring parasitoids and predators keep their numbers in check. The most serious outbreaks occur when mealybugs are introduced accidentally to new countries without natural enemies.

Papaya mealybug spread

The trade in live plant material, such as papaya fruits and seedlings, has accidentally accelerated the spread of papaya mealybug outside its native range. This pest threatens food and nutrition security and adversely affects the safe trade and competitiveness of the agricultural sector for many countries.

Without natural enemies to manage outbreaks, farmers often turn to pesticides. The lack of registered pesticides results in farmers using highly hazardous chemicals that are not only ineffective but can negatively impact native insect biodiversity such as pollinators and natural enemies of pests. A more ecologically sound approach to management is the use of biological control.

Rapid Rural Appraisal of papaya mealybug

As part of the PlantwisePlus programme, CABI in collaboration with the National Agricultural Research Organisation (NARO, Uganda), conducted a Rapid Rural Appraisal (RRA) of papaya mealybug in Uganda. The appraisal sought to gain an understanding of the presence, distribution, and impact of papaya mealybug in Uganda as well as farmers’ management practices. The evaluation also assessed farmers’ willingness to adopt and use biocontrol and their information requirements around biocontrol products.

Information from the appraisal will be used to design an integrated management strategy for papaya mealybug as well as help target community-level communications.

Papaya mealybug on fruit
Papaya mealybug on a papaya fruit

A major cash crop

The seventeen focus group discussions brought together papaya growers from four districts: North District (Lira), Central District (Kayunga, Luwero and Mukono). The districts captured a diversity of farming systems, agro-ecological zones, and agricultural potential. Papaya is a major cash crop for farmers in these districts, in addition to pineapple and traditional cash crops such as coffee. The average farmer cultivates the crop on 0.75-2.5 acres.

The participants confirmed papaya mealybug is already widespread in all four districts where it causes damage to several crops, not just papaya. Farmers started observing the pest between 2017 and 2019 with most saying it is a serious pest that can cause up to 100% crop loss. The official pest reporting to IPPC took place in 2021.

Papaya mealybug management

Farmers mainly attributed the papaya mealybug outbreaks to low productivity and poor-quality fruits. They observed that trees take longer to bear fruit and when they do, they only last one season compared to an average of 4 before. It was estimated that before the pest invaded, farmers obtained UGX 6-8 million/acre each season (£1,800), but currently only obtain UGX 1 million/acre each season (£230).

Regarding management options, commercial farmers reported using pesticides to deal with outbreaks. However, managing papaya mealybugs with pesticides is not always successful due to the pest’s waxy covering. In addition, misuse and/or improper use of these pesticides exacerbate pest problems by reducing beneficial organisms and natural enemies and negatively impacting biodiversity, human health and environmental safety. Further, some farmers don’t observe pre-harvest intervals, thus toxic substances are likely to enter the human food chain posing long-term health risks to consumers and the environment.

Papaya on a farm infected with papaya mealybug
Papaya on a farm infected with papaya mealybug

Sustainable options

Biological control represents a sustainable and effective management option, however, the farmers interviewed had mixed views on the method and the efficacy of the parasitoid in Uganda’s agroecologies. This highlights the importance of proper testing and community-level communications before the introduction of exotic natural enemies. Farmer and community engagement, and mass awareness are key in pest identification and management, especially with the promotion of unfamiliar pest management options. Extension in particular plays a vital role in the research and advancement of low-risk options.

However, one of the main takeaways from the appraisal was farmers’ papaya problems extend beyond papaya mealybug. Farmers reported other associated viral and bacterial diseases causing challenges, including bunchy top disease and leaf necrosis. As such, it is important that researchers assess the economic damage, effect and losses due to papaya mealybug and the associated pests and diseases before releasing biological control parasitoids.

Implementing a biocontrol programme

The PlantwisePlus programme is now looking at the activities required for the implementation of the biocontrol programme in Uganda. In particular, they are developing extension and farmer training manuals to cover papaya crop integrated pest management. These will include papaya mealybug as well as other pests affecting papaya production in the country. In addition, continuous community engagement and mass awareness campaigns will help farmers and their communities manage this highly destructive pest in a more sustainable way. 

PlantwisePlus is working to reduce the reliance on high-risk farm inputs that have adverse effects on human health and biodiversity. By implementing biological control programmes, PlantwisePlus is responding to the challenge and working to improve livelihoods through sustainable approaches to crop production.

About PlantwisePlus

PlantwisePlus is supported by contributions from the UK Foreign, Commonwealth and Development Office, the Swiss Agency for Development and Cooperation, the Netherlands Ministry of Foreign Affairs and the European Commission (DG INTPA).

PapayaPapaya mealybugParaccous margniatusUgandaplant healthplant pestsplantwiseplus

Agriculture and International DevelopmentCrop healthInvasive species

Weedy rice has become herbicide resistant through rapid evolution

Aggressive, herbicide-resistant weed is a threat in nation’s largest rice production region

Date:September 8, 2022Source: Washington University in St. Louis

Summary: Weedy rice is a closely related cousin of crop rice. It aggressively competes with cultivated rice in the field, leading to loss of yield and reductions in harvest quality that compromise market value. Biologists used whole-genome sequences of 48 contemporary weedy rice plants to show how herbicide resistance evolved by gene flow from crop rice. Almost all other cases of herbicide resistance in agricultural weeds result from selection of tolerant genotypes in the weed species.Share:

FULL STORY


In a paper published Sept. 8 in the journal Communications Biology, scientists from Washington University in St. Louis and the University of Arkansas report that a crop pest called weedy rice has become widely herbicide resistant in regions where herbicide-resistant rice is planted. The study highlights challenges facing U.S. rice farmers when they battle a weedy enemy that is closely related to a desirable crop plant.

The genetic investigation was conducted with samples gathered in rice fields in Arkansas, where almost 50% of the nation’s rice is grown.

Weedy rice is a closely related cousin of crop rice. It aggressively competes with cultivated rice in the field, leading to loss of yield and reductions in harvest quality that compromise market value. Weedy rice infestations cause an estimated $45 million in economic losses in the United States each year and hundreds of millions of dollars worldwide.

Biologists used whole-genome sequences of 48 contemporary weedy rice plants to show how herbicide resistance evolved by gene flow from crop rice. Almost all other cases of herbicide resistance in agricultural weeds result from selection of tolerant genotypes in the weed species. Just 20 years after herbicide-resistant rice was first adopted in the southern United States, the majority of fields with a history of herbicide-resistant rice cultivation have weedy rice plants that are also herbicide resistant.

“Throughout its nearly 200-year history in the United States, weedy rice had a very low rate of outcrossing with cultivated rice,” said Marshall Wedger, a postdoctoral research associate in biology in Arts & Sciences at Washington University and first author of the study. “We found that U.S. weedy rice has persisted through herbicide pressure with the survival of those few plants that outcross, consequently acquiring the herbicide- resistance trait.”

“Technological changes in U.S. rice farming since the 2000s have led to a complete genetic revolution in the makeup of the weedy rice that infests U.S. fields,” said Kenneth Olsen, professor of biology at Washington University and senior author on the study.

“In the last 20 years, weedy rice has gone from being very genetically distinct from U.S. crop varieties to nowadays mostly being derived from crop-weed hybridization,” Olsen said. “The weeds are grabbing certain traits from the crop that are beneficial to them, including herbicide resistance.”

Weeds seize their moment

Weedy rice is a scourge of cultivated rice production around the world. But up until the early 2000s, weedy rice in U.S. fields rarely interbred with the kinds of rice that were commonly grown in this country.

Crop rice and weedy rice are the same species, so they are able to interbreed, or hybridize. Their rate of hybridization rate is usually low — generally less than 1% — because rice is self-pollinated.

But something happened that changed the centuries-old dynamic between these two closely related plants. Starting in the early 2000s, two new kinds of crop rice were adopted in U.S. fields. One was a new hybrid rice that offered substantially enhanced yield, compared with traditional inbred (self-pollinating) rice cultivars. The other was a new kind that had been tweaked to be tolerant to a certain kind of herbicide. These so-called Clearfield™ cultivars allowed farmers to plant rice and then apply chemicals to their fields to kill weedy rice and other agricultural weeds without harming the crop.

As early as 2004, just two years after the new rice was adopted locally, Arkansas farmers already were reporting some cases of herbicide resistance in weedy rice. Such resistant plants were likely outcrosses with herbicide-resistant rice.

“The situation is somewhat analogous to human health and the emergence of antibiotic-resistant bacterial pathogens. Widespread use of antibiotics ends up strongly selecting for the rapid evolution of the drug-resistant strains,” Olsen said. “With weedy rice, herbicide-resistant weeds were being detected just a couple of years after herbicide-resistant rice was first commercialized.”

How did it happen? For gene flow from a crop into a weedy relative to occur, the two have to be growing in close enough physical proximity for pollen transfer.

“The herbicide-resistant weedy rice plants are the products of outcrossing with herbicide-tolerant crop,” said Nilda Roma Burgos, professor of weed physiology at University of Arkansas and a co-author of the study. “Outcrossing occurs when weedy rice is not controlled 100% by the herbicide and the remaining weedy rice plants flower at the same time as the herbicide-tolerant rice crop.”

Rice and weedy rice certainly grow in the same fields. However, it was the hybrid rice’s pesky habit of producing volunteers — that is, successfully developing and dropping seeds that overwinter and then emerge as new plants in subsequent years — that opened a door for weedy rice.

The crop volunteers grew up exhibiting variable traits, including changes to flowering timing that made it much more likely that they would swap pollen with weedy rice.

“As a de-domesticated weedy relative, weedy rice has always been able to outcross with cultivated rice. Based on our results, this ability to interbreed is what led to most of the herbicide resistance that we see today,” Wedger said.

A uniquely challenging year for growers

The findings from this new study are being reported during a uniquely challenging year for Arkansas rice farmers. Problems with the global supply chain, as well as increases in the costs of key crop inputs such as fertilizer, have made growing rice more difficult and expensive.

At the same time, global climate change is having local effects on the timing of when rice can be planted. This year, farmers had to cram in planting that usually takes place over a period of four weeks into a much-shortened window. Also this year, nighttime temperatures in northeastern Arkansas were stubbornly high during the months of July and August, with possible negative effects on rice yields. Only time will tell what the 2022 harvest, beginning this month, will bring.

One thing is certain, though: The rapid adaptation of weedy rice to herbicide application serves as yet another example of the dangers of relying on single methods of control for agricultural pests, study authors said.

“How quickly a resistant weedy rice population builds up to a point where the herbicide is no longer useful depends on how the producer manages the herbicide-tolerant rice technology,” Roma Burgos said. “There are best management practices guidelines that help growers avoid resistance evolution for a long time, if implemented.”

“Just like in the case of antibiotic resistance, the rise of resistance to this particular herbicide will be met with a new technology that relies on a new herbicide,” Wedger said. “New herbicide-resistant cultivars are already in development, so I expect this process to repeat.”


Story Source:

Materials provided by Washington University in St. Louis. Original written by Talia Ogliore. Note: Content may be edited for style and length.


Journal Reference:

  1. Marshall J. Wedger, Nilda Roma-Burgos, Kenneth M. Olsen. Genomic revolution of US weedy rice in response to 21st century agricultural technologiesCommunications Biology, 2022; 5 (1) DOI: 10.1038/s42003-022-03803-0

Scientists sleuth out an elusive plant pathogen in Mexico

For years, scientists and online databases presumed the presence of clubroot—one of the main diseases on cruciferous crops (such as broccoli, cabbage, and kale)—in Mexico. However, no evidence to support this supposition existed until a team of researchers, led by Mauricio Luna and Legnara Padrón-Rodríguez of the University of Veracruz, donned their detective caps to pinpoint the clubroot pathogen.

Since Mexico is the world’s fifth largest broccoli producer and the main supplier to the eastern United States and Canada, determining the pathogen’s presence is important when preparing for potential outbreaks. Legnara Padrón developed the detection methodology during COVID-19, causing the authors to consider what could happen if a future pandemic affects plants. The methodology involved working alongside cruciferous crops growers in Mexico and collecting soil samples from three categories of fields: fields in production, fields without cruciferous crops for up to a year, and fields that had stopped growing cruciferous crops. They were able to extract the clubroot pathogen after growing an array of cruciferous crops plants in the soil collected. Typical clubroot symptoms appeared in the roots of infected plants, and the results were confirmed using molecular methods.

Now researchers can investigate if, as suspected, the clubroot pathogen has hindered the growth of cruciferous crops in certain Mexican fields. New fields affected by the disease have been added to the ClubrootTracker, an online tool developed by Dr. Pérez-López’s group to trace the clubroot pathogen. Additionally, their results will significantly improve the future management of clubroot, safeguarding the cruciferous crops economy in Mexico and the worldwide supply of these important vegetables.

Corresponding author Edel Pérez-López comments that their “results open the door to more exciting research, like studying the genome of P. brassicae Mexican isolates, geographic distribution, and its evolution compared to other North American isolates. The strategy we followed could help detect the clubroot pathogen in other geographic areas, or potentially, other soil-borne pathogens.”

Read the complete research at www.phys.org.

Legnara Padrón-Rodríguez et al, Plasmodiophora brassicae in Mexico: From Anecdote to Fact, Plant Disease (2022). DOI: 10.1094/PDIS-11-21-2607-RE 

Publication date: Wed 14 Sep 2022

Scouting pests and diseases

As a grower, you want to have an overview of what’s happening in your crop at all times. This is why many growers make sure that scouting takes place at regular times. Natutec Scout is a tool developed by Koppert to make sure every grower can utilize the benefits of having all your scout data in one central place.

To accommodate growers’ way of working, Natutec Scout offers four different ways to input your data:

  • Pen and paper scouting: write down your observations on paper like you’re used to, and enter your findings straight and simply. Record your findings directly into Natutec Scout using the manual input feature. Input is easier and quicker than using Excel with all the benefits and tools that Natutec Scout provides.
  • Enter your observations on the mobile Natutec Scout app – available for both Android and iOS – in which you make your observations, provide your location, and add notes and photos if you want to add additional findings to your scouting session. This data is then uploaded to the dashboard.
  • Automatic detection of whitefly using the Horiver Scanner: Using the power of Artificial Intelligence (AI) for automatic whitefly counts enables you to save a significant amount of time and labor when counting the whitefly on Horiver cards. Just take a picture of a Horiver card, and you are done.
  • Import historical scout data using the Excel import functionality. You can easily load multiple years of previous scout data (averages and specifics) into Natutec Scout. You immediately get the tools at your disposal to discover trends, hotspots, and other significant events in the IPM of your crop.

The scout data are transferable. Because of that, it’s nice to work with this knowledge between everyone in your company and for your external consultant(s).

For more information:
Koppert Biological Systems
koppert.com

Publication date: Wed 14 Sep 2022

Scouting pests and diseases

As a grower, you want to have an overview of what’s happening in your crop at all times. This is why many growers make sure that scouting takes place at regular times. Natutec Scout is a tool developed by Koppert to make sure every grower can utilize the benefits of having all your scout data in one central place.

To accommodate growers’ way of working, Natutec Scout offers four different ways to input your data:

  • Pen and paper scouting: write down your observations on paper like you’re used to, and enter your findings straight and simply. Record your findings directly into Natutec Scout using the manual input feature. Input is easier and quicker than using Excel with all the benefits and tools that Natutec Scout provides.
  • Enter your observations on the mobile Natutec Scout app – available for both Android and iOS – in which you make your observations, provide your location, and add notes and photos if you want to add additional findings to your scouting session. This data is then uploaded to the dashboard.
  • Automatic detection of whitefly using the Horiver Scanner: Using the power of Artificial Intelligence (AI) for automatic whitefly counts enables you to save a significant amount of time and labor when counting the whitefly on Horiver cards. Just take a picture of a Horiver card, and you are done.
  • Import historical scout data using the Excel import functionality. You can easily load multiple years of previous scout data (averages and specifics) into Natutec Scout. You immediately get the tools at your disposal to discover trends, hotspots, and other significant events in the IPM of your crop.

The scout data are transferable. Because of that, it’s nice to work with this knowledge between everyone in your company and for your external consultant(s).

For more information:
Koppert Biological Systems
koppert.com

Publication date: Wed 14 Sep 2022