A tree-lined path at Washington University’s environmental field station, Tyson Research Center, located near Eureka, Mo. Credit: Tyson Research Center
A large study involving 43 research plots in the Forest Global Earth Observatory (ForestGEO) Network—including a swath of trees at Tyson Research Center, the environmental field station of Washington University in St. Louis—has helped clarify the power of underground fungi to shape forests.
From the tropics to the far north, fungi in the soil seem to directly determine the number and types of trees that can thrive in a given area, said Jonathan Myers, an associate professor of biology whose work at Tyson contributed to the global findings. The study was published in Communications Biology.
Many trees depend on a special partnership with mycorrhizal fungi that grow around their roots. The fungi provide the tree with nitrogen, phosphorus and other nutrients, and the tree gives the fungi carbon in the form of sugar and lipids for energy. “It’s a mutually beneficial arrangement,” Myers said.
The results from this study suggest that fungi are more than casual acquaintances with their tree companions: the fungi drive diversity—or lack thereof.
Specifically, the underground back-and-forth helps explain why tropical forests can support multiple species of trees in a small area, why forests in the far north and south are often dominated by just a few species, and why the oak and hickory forests at Tyson fall near the middle of the diversity spectrum. “The study really zeroed in on one of the basic patterns in ecology, which is that forests become more diverse the closer you get to the equator,” Myers said.
Researchers used mathematical models and tree surveys to track the impact of different types of mycorrhizal fungi on diversity. As Myers explained, these come in two main types: arbuscular mycorrhizae (AM) and ectomycorrhizae (EM). AM fungi—”living fossils” that are essentially identical to the fungi that partnered with the earliest plants known to science—are especially abundant in the tropics. EM fungi, a newer arrival to the scene, become increasingly common farther from the equator.
The study suggests that a shift from one type of fungi to another has had major consequences for tree diversity. AM fungi are equal-opportunity partners that will support just about any AM tree species that happen to live nearby. Because the fungi are not too picky, any AM seedling or sapling trying to grow in a given spot can expect a boost from the local mycorrhizae.
EM fungi, in contrast, are much more discerning and will only help certain tree species—spurning all others. As a result, a sapling that depends on EM fungi is more likely to thrive if it can share space—and fungi—with a member of its own species. In that way, choosy fungi encourage communities of trees of the same species to cluster together.
EM fungi also help protect their favored species of trees from diseases. As Myers explained, this helpful action actually makes forests less diverse. If a forest suffers a disease outbreak that targets a specific type of tree, it could be risky to grow too close to a neighbor of the same species. But EM fungi reduce that risk, making it safer for trees to grow close to their own kind. AM fungi don’t offer as much disease protection, so trees in tropical forests find safety in diversity.
A better understanding of fungi helps put the trees of Tyson into perspective, Myers said. Roughly halfway between the tropics and the boreal forests of northern Canada, Tyson is home to both of the kinds of fungi examined in the study. It also boasts a moderate mix of trees—mostly varieties of hickories and oaks— that is neither wildly diverse nor unrelentingly monotonous. Tyson’s position between the extremes made it a valuable source of data for the global study, Myers said.
“We have just over 40 different species of trees on the plot that we studied, which is the size of about 45 football fields,” Myers said. “In most tropical forests, there would be hundreds of different species in a plot that size. In the boreal forests of northern Canada, there might be fewer than 10.”
To further understand the forces driving forest diversity, researchers should study exactly how fungi interact with tree roots at a physical and chemical level, Myers said. “We have a lot more work to do underground,” he said.
More information: Camille S. Delavaux et al, Mycorrhizal feedbacks influence global forest structure and diversity, Communications Biology (2023). DOI: 10.1038/s42003-023-05410-z
The USDA Forest Service funds hundreds of projects every year to protect our nation’s woodlands. Included in these research projects are several different types of pest management strategies spanning a wide range of pests, forest types, and ecosystems. A new article in theJournal of Integrated Pest Managementreviews USFS pest-management research from 2011 to 2020, which helped manage over 2.2 million hectares of forest. (Photo byUSDA Forest Service via Flickr, public domain)
Folks outside the forest entomology realm have likely heard of the USDA Forest Service but may have little knowledge of what this group actually does. Truth be told, they do a lot—from trail and road maintenance to fire suppression and prevention to management, this group is responsible for managing millions of acres of our nation’s forestland. But, in addition to the management aspect, the Forest Service (USFS) also conducts and funds research—lots of research. In anarticle published in October in theJournal of Integrated Pest Management, several USFS scientists summarize the past decade’s USFS-funded forest health management, and, frankly, the impacts on U.S. forests are impressive.
Forest Health Protection is a unit of the USFS State, Private, and Tribal Forestry Deputy Area, and this group regularly works with personnel from academia, government, industry, and nonprofit organizations to monitor pests and improve management of forests. New and existing grants are funded annually, and, while many of these projects result in peer-reviewed publications, this is the first time their impact has been summarized in one place.
In total, over 2,400 forest pest-management projects were supported between 2011 and 2020, directly impacting 2,284,624 hectares (5,645,429 acres or 8,821 square miles). The list of pests impacted by this work reads as theWho’s Whoof forest health issues and includes native species such as the mountain and southern pine beetle, Douglas-fir beetle, western spruce budworm, and Ips bark beetles. Invasive pests include the spongy moth, emerald ash borer, and hemlock woolly adelgid. Projects evaluated traditional and novel management methods, and the paper contains a plethora of interesting numbers and facts related to this program—way more than can be adequately summarized here.
The USDA Forest Service funds hundreds of projects every year to protect our nation’s woodlands. Included in these research projects are several different types of pest management strategies spanning a wide range of pests, forest types, and ecosystems. A new article in theJournal of Integrated Pest Managementreviews USFS pest-management research from 2011 to 2020, which helped manage over 2.2 million hectares of forest. (Image originally published in Coleman et al 2023,Journal of Integrated Pest Management)
But, as someone who works in the forest health realm and who works with the USFS very frequently, a few points are worth highlighting. First, the tables and figures alone in this paper holdso muchinformation on where federal funding goes and what it impacts. This is a common criticism from those who might not appreciate what our federal government does or where tax dollars go, and this paper goes a long way to help answer some of these questions as they pertain to USFS work. From the data, it seems clear that a lot is being done because of this program. Second, the question of where in the country our federal dollars go is also largely answered, as the authors clearly break down where the projects took place, acres impacted in each region, and several other location-specific bits of information. Finally, the comprehensive nature of this program is well-documented in this paper. It’s not just bark beetles, or defoliators, or native or invasive species—it’s all of them at the same time. It’s broad-scale forest health work, which is an excellent goal and objective for an entity such as the USDA Forest Service.
Whether you work in forests or not, this paper does an excellent job of summarizing a decade of government-supported integrated pest management work.
David Coyle, Ph.D., is an assistant professor in the Department of Forestry and Environmental Conservation at Clemson University. Find him on all the socials as@drdavecoyle. Email:dcoyle@clemson.edu.
Gilbert Barrantes / Laura Segura Hernández / Diego Solano Brenes
Gelanor siquirres, a species of pirate spider, descends from its dragline while pursuing prey in a Costa Rican rainforest.
Headlamps alone illuminated the trail bisecting the Costa Rican rainforest. Having waded the black of the Tirimbina reserve so often before, Gilbert Barrantes, Laura Segura Hernández and Diego Solano Brenes knew the routine.
It was time, dusk informed the surrounding spiders, to let loose the wind-aided, floating lines of silk that might latch onto leaf, branch or ground, fortifying the first beams of the food-snaring webs to come. But even on a night so familiar, the team would encounter a hunting scene unfamiliar not just to these arachnologists, in this forest, but all of them, anywhere.
“It was completely serendipitous,” said Segura Hernández, who earned her doctorate from the University of Nebraska–Lincoln in August.
What the trio stumbled on was a trap: lines floated not for framing but for fishing, part of a gambit that gives other forest-dwelling spiders just enough silk to hang themselves. And at the center of the scheme, not to mention the lines? A venomous pirate.
Four lines of that silk, the researchers realized, were running horizontally and diagonally from the underside of the same leaf. From elsewhere, the end of another thread had drifted in and caught on one of those leaf-dangling lines. That thread was the product of a spiderling now skittering along it to inspect the joint and, with its silken pillar secured, commence the construction of a full-fledged web.
“And then,” Segura Hernández said, “we just saw this other spider shoot in out of nowhere.”
The interloper was Gelanor siquirres, a species from the family known as pirate spiders — named for their willingness to invade already-built spider webs, strategically pluck threads to draw out their eight-legged inhabitants, and dine on them. This was something different. This G. siquirres emerged from its hiding spot beneath the leaf, scuttled across its own floating line, paralyzed its harried, hapless prey with a bite, then retreated to the leaf with the spiderling clutched in its ultra-long jaws.
A close look at that leaf would reveal the swashbuckler’s identity. A close look at the research literature would reveal that no one had ever reported the devious hunting technique, which the team has since witnessed multiple times. With a recent paper in the journal Animal Behaviour, the Tirimbina-trekking team would become the first.
“It’s working as a spider web for catching spiders,” Segura Hernández said of the lines floated by G. siquirres, which, like its pirate brethren, does not build circular webs. “That’s one of the cool things about it.”
Not the only thing, though. Pirate spiders are known as slow, deliberate killers: While venturing onto another spider’s web, Segura Hernández said, some pirates might advance no more than a few centimeters in an hour, lest they risk triggering any unwanted vibrations. The stealth makes sense when considering that the prey are also accomplished predators with venom of their own, and that G. siquirres, at no more than a half-inch long, is more David than Goliath.
Yet when another spider approaches one of its floating lines, G. siquirres darts forward with an alacrity that initially stunned Segura Hernández and her colleagues — the equivalent of a sloth turning cheetah.
“So it’s not just a modification of web-building behavior,” she said. “It’s a modification of the spider’s locomotion, as well.”
Footage of a pirate spider capturing a smaller arachnid before retreating to a leaf.
G. siquirres seems to have adapted its schedule, too, getting an early start to ensure that its floating lines are in place by the time its potential prey is releasing its own.
“It’s not like spiders make webs all night,” Segura Hernández said. “There’s clearly a peak period of activity, right after dark, where you see all of these floating lines on the trail. So it’s not like (G. siquirres) can do this in the morning. They are targeting this specific time period.”
There remains a lot to learn about G. siquirres, which was officially described and named in 2016 but had not, until now, been the subject of any peer-reviewed research. The fact that the first G. siquirres behavior ever documented happens to double as a behavior never seen in any spider speaks to how much remains unknown about the eight-legged wonders as a whole, Segura Hernández said, especially those residing in prey-rich rainforests.
G. siquirres feeding on its prey, an immature spider (white arrow) that touched the silk line its predator had earlier floated as a trap.
For her, it also underscores the value of not overlooking observation itself, of remembering to seek ideas, questions and answers not just in pages but the wild. She hasn’t forgotten the words of Bill Eberhard, who mentored her as an undergrad at the University of Costa Rica and was commemorated in the same journal issue that features the G. siquirres study.
“One of my favorite things about this paper is that it highlights how important it is — what Bill Eberhard taught us — to observe and just pay attention to detail,” she said. “Sometimes people are so focused on hypotheses and questions that they kind of forget about the organisms. But I think both things are equally important.
“Can we even envision how many more incredible hunting strategies there are just waiting to be observed?”
It was that spirit, in part, that encouraged her to spend so much time wandering in Tirimbina. At this point, she can’t recall any specific reason that she and the others were out that fateful night. Not that she needed one. The rainforest itself — the trill of insects and pattering of lizards, the aromas of wildflowers floating, like the spider silk, on a breeze — offered its own draw.
“Everything is alive. And at night, it has a mystery. You realize how much you rely on vision, because you’re restricted to what your headlamp can show.
“But that one time, we were just walking down the trail, talking about something,” she said, “and then we noticed the silk.”
The photography of partial plants in two control groups and four treatments. We selected 11 images for each group of plants, including plants at the median leaf diameter of each treatment in the middle of the row, as well as five slightly larger and five slightly smaller plants on the left and the right. Each row of images shares one ruler, which is given in the image on the far right. The identifier of each image is given at the bottom of each image. Credit: Communications Biology (2023). DOI: 10.1038/s42003-023-05391-z
A team of agronomists and biotechnicians at China Agricultural University has found that adding bacteria to simulated lunar regolith increased the amount of phosphate in the soil for use by plants. In their study, published in the journal Communications Biology, the group added three types of bacteria to samples of volcanic material and then tested them for acidity and their ability to grow plants.
As several countries make plans to send humans back to the moon, they must address several issues—one of the most basic is figuring out a way to feed people working there for an extended period of time. The obvious solution is for workers to grow their own food. But that presents problems, as well, such as how to transport soil for growing edible plants from Earth to the moon.
Some have suggested that moon soil, known as lunar regolith, might be treated to make it amenable to plant growth. Last year, a team in the U.S. showed that it is possible to grow plants in lunar regolith by growing a small number of weeds called thale cress in real lunar soil samples. That test showed that lunar soil can work, but not well enough for plants to mature and produce food. In this new study, the research team found that adding microbes to lunar soil can improve its ability to host plant life.
To test the possibility of using microbes such as bacteria to make lunar regolith more hospitable to plant life, the research team obtained samples of volcanic material from a mountain in China—testing showed it to be a reasonable stand-in for regolith. The researchers then added one of three types of bacteria to three test pots filled with the volcanic material: Pseudomonas fluorescens, Bacillus megaterium and Bacillus mucilaginosus.
After cultivating the bacteria in the soil samples, the researchers tested the samples to see the effects. They found that the addition of all three types of bacteria had made the soil samples more acidic, which resulted in reducing the pH level of the soil. That dissolved the insoluble phosphate-containing minerals in the soil, which released phosphorus, making it available for plants.
The research team then directly tested the treated soil by planting Nicotiana benthamiana (benth). They found that the enhanced soil produce plants with more robust roots, longer stems and bigger leaves compared to untreated samples.
More information: Yitong Xia et al, Phosphorus-solubilizing bacteria improve the growth of Nicotiana benthamiana on lunar regolith simulant by dissociating insoluble inorganic phosphorus, Communications Biology (2023). DOI: 10.1038/s42003-023-05391-z
Championing sustainable agriculture by promoting lower-risk plant protection solutions to tackle crop health challenges is a key objective ofCABI’s PlantwisePlus programme. In particular, the managing of plant pests and diseases. A cornerstone of this work is setting up local facilities for the mass rearing of lower-risk plant protection solutions.
As of early 2022, PlantwisePlus in Pakistan had seen advancements in this area. The programme established collaborative agreements with provincial governments to introduce low-cost, low-tech mass rearing facilities in Khyber Pakhtunkhwa (KPK) and Punjab. The focus? Producing the biological control (biocontrol) agent,Trichogramma chilonis. While this parasitic wasp is available in Pakistan, the PlantwisePlus programme aims to introduce a more commercial-scale production. Thus increasing the capacity to produce and supplyTrichogrammato farmers.
Showcasing the tiny parasitic wasp in the piloted mass rearing facility.
What isTrichogramma?
Trichogramma chilonisinserting its egg into a fruit borer egg
Trichogramma chilonisis a tiny parasitic wasp that targetsHelicoverpa armigera, also known as the tomato fruit borer. In Pakistan, the tomato fruit borer is a significant pest of tomato. The presence of the pest has historically led farmers to resort to heavy pesticide applications, butTrichogrammaoffers a sustainable solution.
Compared to other countries, tomato crop production is low in Pakistan, due to pests and diseases.Studies have foundthat the tomato fruit borer causes over 50% of fruit losses in the Peshawar district of KPK.
Trichogrammais a natural enemy of the tomato fruit borer and can be used as a biological control (biocontrol) agent.Biocontrolis an effective method of controlling a pest’s numbers and spread without harming the environment. It is a safe alternative to the use of pesticides and, in particular, highly hazardous pesticides.
Trichogrammamass rearing in Pakistan
Although several government agricultural departments in Pakistan already produce lower-risk plant protection products, their facilities and processes can be optimized.
So far, PlantwisePlus and local government partners have established threeTrichogramma mass rearing facilities (TRF) in Pakistan. The first TRF was set up in 2022 in Mardan, KPK. This facility is now operational, producing and distributingTrichogrammacards to farmers. Earlier this year, the programme also established a facility in Muzaffargarh, South Punjab. And most recently, work has begun on a third facility in Muzaffarabad, Azad Jammu and Kashmir.
As well as working with local partners to construct or renovate these facilities, PlantwisePlus has also provided expert training to facility staff. Staff from CABI’s Regional Centre in Rawalpindi has provided technical support to the establishment of the TRFs in KPK and South Punjab. Whilst more detailed training, on the establishment of a large-scale rearing approach and quality control, has been supported by international experts from CABI Switzerland.
This training helps local staff move from laboratory-scale production to mass rearing that serves the wider farming community.
Using mass rearing to help smallholder communities
MakingTrichogrammamore widely available to smallholder farmers ensures they spend less on chemical controls. Although periodic releases ofTrichogrammaare necessary, they are far less frequent than spraying pesticides.
The reduction in chemical use also benefits farmers’ health and supports biodiversity. Chemical pesticides are indiscriminate, also harming populations of beneficial insects. Biocontrol uses nature’s in-built mechanisms to help restore balance.
Used as part of an Integrated Pest Management orIPM strategy,Trichogrammacomplements other physical, cultural, and (judicious) chemical techniques. In light of this, PlantwisePlus also supports local extension staff with training. This ensures that smallholder farmers can access sound agricultural advice and apply IPM techniques appropriately and to their full potential in the field.
Pesticide risk reduction with PlantwisePlus
PlantwisePlus aims to increase awareness of, access to, and use of affordable IPM solutions. This includes biocontrol as part of an IPM system. The programme recognizes the urgent need to increase the uptake of lower-risk plant protection products. Andreduce relianceon high-risk farm inputs.
Through establishing these mass rearing facilities, PlantwisePlus is enhancing partners’ ability to produce their own augmentative biological control solutions. This creates opportunities for farmers to apply safer practices in place of chemical pesticides.
As the facilities develop and become fully operational, PlantwisePlus will investigate whether they can provide a model for successful local agribusinesses. Can they create sustainable employment as well as change farmers’ attitudes to using lower-risk plant protection products? The hope is that they can, and the model can be scaled up in Pakistan and out to other programme countries in the future.
Dear colleagues, On behalf of the Hellenic Society of Phytiatry we would like to invite you to participate in the XX IPP Congress which is going to take place at the Megaron Conference center in Athens Greece, in July 1-5, 2024.The Congress is hosted by the Hellenic Society of Phytiatry in Athens, Greece and organized under the auspices of the International Association for the Plant Protection Sciences (IAPPS), and of the Agricultural University of Athens. In an era of the undoubted phenomenon of climate change around the globe, in a period of the vast increase of earth population with immense problems in food security, in a period of enormous pressure on natural resources to meet α vast need for nutritious and safe food, conservation of biodiversity and creating opportunities for economic growth, Plant Protection will play an extremely important universal role in securing human welfare. Management of Crop Loss caused by pathogens and pests is a complicated issue of paramount importance for global agriculture, involving hosts and environment, plus scopious and intense scientific research, political decisions and application of international rules and measures. There is an urgent need for developing ecofriendly and safe biologicals and agrochemicals, pesticides either with nano-formulations. Research is also required to study evolutionary dynamics in reference to climate change, measurements and analysis, modelling of crop loss and predictive modelling. So, there is an urgent need to identify new pests and efficiently cope with diseases or pests threatening global human welfare. Obviously, new pathogen resistant sources in germplasm for confronting destructive pests and diseases are an everyday request by farmers. In an era of the boom of artificial intelligence able in perceiving, synthesizing, and inferring information—demonstrated by machines, Plant Protection is on the center of international interest. Therefore, the Congress will be consisted of plenary and concurrent sessions of updated information and research data with invited speakers along with oral and poster presentations to cover all plant protection disciplines including plant pathology, entomology, weed science, nematology, plant breeding, technology transfer and relative to plant protection disciplines. Satellite sessions will be also welcomed. Plenary lectures will be among others focused on: Molecular diagnostics for evidence based rational use of pesticides, in the European Green Deal era Enabling sustainable agriculture through understanding and enhancement of microbiomes Applying chemical ecology for environmentally friendly strategies to control insect pests Impact and control of transboundary/invasive banana wilt pathogen, Fusarium oxysporum f. sp. cubense Microbial pesticides: Discovery, piloting and scaling up in Africa Sustainable weed management Coordinated approach for transboundary plant pest and disease management Food security in Africa needs policy support for sustainable plant health management Concurrent Sessions will be generally focus on: Current plant protection problems affecting major regional crops or crops of international significance such as grapevines, olives, citrus, tropical fruit trees, cereals, vegetables, forests etc. will be highlighted. Top scientists will be invited to present updated information on chemical plant protection problems contributing to current advances and alternatives offered by the private sector of agrochemical-pharmaceutical chemistry. Further objectives of the IPPCAthens2024, will be invited lectures and oral presentations on hot research topics and recent developments in Plant Protection sciences directly originating from research translation of molecular plant pest interactions. Scientific contact among young scientists and top research leaders, helping opening research cooperation and contacts with leading research groups around the globe will be promoted and facilitated.
International organizations dealing with food security, food safety and plant health will be welcomed to critically analyze crucial current problems related to world agriculture and propose measures and actions. FAO, EFSA, EPPO and other leading organizations will be invited to participate in this unique Global Plant Protection Congress.
We are confident that as congress organizers will make any effort needed to succeed in organizing a scientifically profitable event and assure you for a memorable stay in Athens Greece. More information regarding the Congress are available at www.ippcathens2024.gr Sincerely yours, The Chairman of the XX IPPCATHENS2024 Eris Tjamos For any further information, do not hesitate to contact Congress Secretariat Panagiotis Georgakopoulos Senior Project Manager Tel: +30 2103250260 email: panagiotis@globalevents.gr
What are bioprotection products, and how do they work?
Bioprotection products are nature-based solutions to managing crop pests and diseases. More and more growers are turning to environmentally sustainable crop pest and disease management solutions, such as bioprotection products. Reasons for choosing more sustainable solutions include pest and disease resistance to chemical pesticides and concerns for human health and the environment.
Ladybird biological control. Image: CABI
Bioprotection products use living organisms such as insects (macrobials) and bacteria, viruses or fungi (microbials). They also include extracts or mimics of naturally occurring substances (semiochemicals).
What are the main types of bioprotection products?
Continue reading to discover the key product categories and how they can help manage crop pests and diseases.
Macrobial bioprotection products
Macrobial products include predator insects, parasitoid insects and nematodes. They all work slightly differently in killing pest insects.
Predator insects work to reduce pest numbers by attacking and feeding on other insects, usually killing several individuals during their life cycle.
Parasitoids
Parasitoid insects kill pest insects by inserting their eggs inside the bodies of pest insects. The eggs then develop and grow inside the body of the pest insect, killing it. The adult parasitoids then emerge from the bodies of the pest insects.
Entomopathogenic nematodes
Entomopathogenic nematodes are elongated, cylindrical worms of the order Nematoda. They are parasitic in animals, insects, or plants. They can also be free-living in soil or water. Nematodes kill pest insects by entering the body of the pest insect and infecting it with deadly bacteria. Some species of nematode reproduce within the body of the pest insect, with multiple nematodes exiting the body of the pest, ready to infect more pest insects.
Microbial bioprotection products
Microbial products include bacteria, viruses and fungi or other microorganisms or their metabolites or cell fragments that have the capacity to kill pests or outcompete and prevent diseases.
Bacteria are single-celled, microscopic organisms that lack a nucleus. When applied to crops, bacterial microbial products do not harm the crop itself. However, they are deadly to pest insects that eat the plant and become infected with the bacteria.
Viral products
Viruses are tiny, infectious particles consisting of nucleic acid and a protein coat, which can only reproduce within the cell of a living host. As with bacterial products, growers can apply viral products to crops without harm to the crop itself. When pest insects eat the plant, the insect becomes infected by the bacteria, causing the insect to die.
Fungal products
Fungi are multicellular organisms that lack chlorophyll and derive nutrients from other organisms. The fungal body generally consists of filamentous strands called mycelium. Fungal products usually work by landing on the body of the pest insect, with spores entering the body. The fungus branches and forms a network of branches inside the body of the insect, killing it. As well as destroying insects, microbial products kill plant-damaging diseases too.
Semiochemicals
Semiochemicals are message-bearing compounds produced by animals or plants that can be used to change and disrupt a pest’s normal behaviour (including sex and aggregation pheromones or various scented plant extracts that attract insect pests to traps).
CABI Academy Introduction to Bioprotection Products Course
Would you like to discover more about bioprotection products? The CABI Academy Introduction to Bioprotection Products course explains what they are, why they’re important and how they work. It gives a practical guide and set of resources to help advise farmers about choosing, using and interpreting the results of such products. The course is online and self-paced and takes approximately 8-10 hours to complete. Topics covered include:
– What are bioprotection products, and how do they work?
– Using bioprotection products to monitor pest insects
– Safety information and interpreting product labels
The CABI BioProtection Portal is an open-access tool that provides users with information about registered biocontrol and biopesticide products in their country. It aims to help growers and agricultural advisors identify, source and correctly apply these products against problematic pests in their crops.
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If you are active in the field of plant health or development and would like to contribute to the Plantwise Blog, please contact Donna Hutchinson. We are happy to post any credible articles that we think would be of interest to our readership.
Views expressed in contributions do not necessarily reflect official CABI or Plantwise positions.
by Sophie Fessl, Gregor Mendel Institut für Molekulare Pflanzenbiologie (GMI)
Microscopic image of turnip mosaic virus (yellow) infecting an Arabidopsis shoot tip. Left: The virus spreads throughout the shoot but is excluded from the small population of stem cells. Right: When RDR1 is missing, the virus also infects the stem cells. Credit: Gabriele Bradamante/GMI
Viruses are a threat to all organisms, including plants. A small group of plant stem cells, however, successfully defends itself from infection.
Marco Incarbone, now at MPIMP Golm, Gabriele Bradamante and their co-authors at the Gregor Mendel Institute of Molecular Plant Biology (GMI) uncovered that salicylic acid and RNA interference mediate this antiviral immunity of plant stem cells. The findings were published in PNAS on October 12.
Plant viruses threaten the health of their hosts, can spread swiftly and globally, and challenge agricultural productivity. When viruses successfully infect plants, the infection often spreads through the entire organism. Well, not entirely: One small group of indomitable cells still holds out, the stem cells within the shoot tip. This small group of cells generates all plant tissues above ground, including the next plant generation, and for reasons still poorly understood, viruses are unable to proliferate in these cells.
Marco Incarbone, previously a postdoctoral researcher in the group of Ortrun Mittelsten Scheid at the Gregor Mendel Institute of the Austrian Academy of Sciences (GMI) and now a group leader at the Max Planck Institute of Molecular Plant Physiology in Germany sought to uncover the molecular bases of how stem cells in the shoot apical meristem fight off viruses together with Ph.D. student Gabriele Bradamante and other GMI group members.
To understand the strong antiviral defenses of this special group of cells, Incarbone, Bradamante and colleagues first established a screening platform. “We developed high-throughput microscopy techniques that allowed us to study many Arabidopsis meristems at several timepoints after the viral infection, to give a temporal dimension to our exploration,” Incarbone explains.
Using this dynamic, semi-quantitative approach, the researchers observed that Turnip mosaic virus—their plant model virus of choice—spreads in their model plant Arabidopsis thaliana, arrives at the stem cells within the shoot tip , and even enters these cells, but is then quickly excluded. “Surprisingly, these cells are really good at driving the virus out.”
Past work on a close relative of tobacco had provided clues that RNA interference—a pathway that inhibits virus proliferation in plants and many animals—plays a role in virus exclusion in plants. In the search for the defense’s molecular bases, the researchers therefore screened Arabidopsis mutant plants that miss certain components of the RNA interference pathway. In addition, they studied plants deficient in salicylic acid, a key plant defense hormone.
Through a series of targeted experiments, the researchers were able to see that during virus infection, salicylic acid production is activated. “The plant recognizes the virus and sets off salicylic acid as an alarm bell.” Salicylic acid in turn activates a key factor in RNA interference amplification, called RDR1. RDR1 ramps up production of double-stranded RNA from viral RNA, giving plants more virus-specific sequences to direct the defense mechanism against the invading virus.
“In the fight against Turnip mosaic virus, both salicylic acid and RDR1 are necessary to expel the virus from the stem cells—however, RDR1 is not produced within the stem cells themselves, but in the tissue below the stem cells and in the vasculature,” Incarbone adds.
“There it generates the RNA-based and most likely mobile information that immunizes the stem cells from the incoming virus. While we know infection triggers an overall increase in salicylic acid, we do not yet know where in the plant and at what time during infection this happens. We are currently trying to solve this puzzle.”
But every virus is different. In the fight against other viruses, salicylic acid and RDR1 are activated but not necessarily required. “Based on our experiments with other viruses we can, however, conclude that RNA interference is always necessary to defend stem cells from infection.”
Still, the stem cells keep a mystery: plant viruses frequently evade and suppress RNA interference in other plant tissues. “Why can viruses suppress RNA interference in most of the plant, but not in these special cells? This remains the big question.”
In follow-up work, Incarbone will now investigate how viruses are stopped from passing into an infected plant’s seeds and offspring– which develop from the protected stem cells. “Our findings add important knowledge about how stem cell antiviral defenses work and give a robust molecular framework to build upon.”
More information: Marco Incarbone et al, Salicylic acid and RNA interference mediate antiviral immunity of plant stem cells, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2302069120
Backlit leaves of an American beech tree show dark bands, a symptom of beech leaf disease. Credit: Heather Faubert
Beech trees from Ohio to New England are losing leaves and dying off in alarming numbers. The American beech, recognizable by its smooth gray trunk, is a key species in many eastern forests and provides nutritious beechnuts favored by animals from woodpeckers to deer to black bears. But now a microscopic worm called a nematode is threatening the trees on a growing scale. As far as plant parasites go, nematodes are common, but they tend to damage the roots. The species of nematode that is causing Beech Leaf Disease (BLD) is different: It afflicts the leaves, and it’s deadly.
“There’s never been a foliar nematode that can cause mortality of a large forest tree like beech,” says Dr. Nicholas Brazee, a plant pathologist at the University of Massachusetts Amherst’s Extension Plant Diagnostics Laboratory. Because there’s no precedent for this kind of pest, there were no obvious treatments to consider when the disease emerged. “Researchers are just kind of starting from ground zero to see what will possibly work,” he says.
The telltale signs of beech leaf disease—and the challenges of treating it—can be traced back to the nematode’s cycle of movement. They occupy the leaves themselves during spring and summer, reproducing all the while, and then migrate into new leaf buds from late summer into fall. The nematodes overwinter inside the buds, feeding on developing leaves and laying eggs. In spring, both eggs and nematodes in all stages of life can emerge along with the young leaves when the buds open.
How To Identify Beech Leaf Disease
Beech leaf disease affects the American beech (Fagus grandifolia), a tree found in forests across the Eastern United States and parts of Canada, as well as European and Oriental beech that are grown ornamentally.
“This has got to be one of the easiest diseases to make an identification,” says Dr. Richard Cowles, an agricultural scientist at the Connecticut Agricultural Experiment Station.
It shows up in about the same way across beech species: Looking up at a leaf, the light shining through reveals dark bands between veins extending out from the central vein. Looking down at the top of the leaf, the bands may not be visible until fall, when they can appear yellowish.
On an American beech tree infected with beech leaf disease, the characteristic leaf bands are yellow in fall. Credit: Heather Faubert
The banding symptom of BLD is caused by nematodes inside the original leaf bud. There, the nematodes interfere with the leaves’ development, causing cells to grow larger and in thicker layers. When leaves emerge from the buds in spring, they already have the unmistakable bands. In the course of the growing season, affected leaves can distort, brown, and thicken. The dark bands can also be raised, bending the surface of the leaf into a convex cupping shape. Affected leaves eventually fall off the tree earlier than a healthy leaf would.
As the disease progresses year after year, buds may become so infested with nematodes that they consume all the leaf tissue in the bud, preventing the leaves from emerging at all. Without new leaves to photosynthesize, branches die.
“First little twigs and then entire branches and then probably the whole tree would die because they don’t have any functioning leaves anymore,” Cowles says.
American beech with crinkled, leathery leaves due to severe beech leaf disease. Credit: Heather Faubert
This progression of infection and die-off tends to happen from the bottom of the tree upward. Cowles says this is because rain washes nematodes down the tree, where they accumulate on the lower branches. The ease with which nematodes are transported by water may also explain why BLD appears to progress more quickly in trees in New England than in trees in Ohio.
“We have a more humid climate here [than in Ohio] and we have rain events that are very conducive to the successful migration of the nematodes from the leaves to the buds,” Cowles says.
But it’s probably not just water transporting the nematodes. Scientists believe they may be carried by birds and insects as well as the many animals that feed on beechnuts—which emerge late in the growing season when nematode populations are at their highest, Cowles says.
The Forest Vs. The Trees
After beech leaf disease appeared in northeastern Ohio in 2012, it radiated out to the surrounding region and Ontario, Canada, Brazee says. Then in 2019, it jumped east, showing up in southwestern Connecticut and neighboring Long Island, and spread quickly from there. It’s now in at least a dozen states, with Vermont reporting its first case this month.
Because beech trees grow together in stands and the disease is spreading so quickly, neither Cowles nor Brazee thinks it can be stopped.
“The forest situation is fairly hopeless,” Cowles says. But Brazee points out that it will eventually slow. We’re in an early “killing front” phase of the epidemic, with the nematode sweeping through in huge numbers, he says.
“At some point when there is this big die-off of beech, the nematode population will decline and it’ll probably be much easier to manage it,” he says. “But we have no idea how long that’ll take.”
The outlook may not be as bleak for ornamental trees. Part of what makes BLD so tough to beat is constant reinfection from surrounding trees. But for individuals isolated from other beeches, as those in gardens or landscaped areas might be, it may be easier to keep nematode populations in check, Cowles says.
Treatment Options
Researchers are studying several different approaches to treatment, and while some chemicals show promise, the specifics of application—how much, how often, what time of year—are still unclear. It can take years to understand the effects of a treatment on a tree, and the disease hasn’t been around long enough for researchers to gather the data they need to fill in those gaps and make concrete recommendations. As a reminder, it’s best to speak with a licensed professional before purchasing or applying a pesticide.
The underside of American beech leaves that are crinkled and leathery due to severe beech leaf disease. Credit: Heather Faubert
One product that’s had positive results in early research is a fungicide and nematicide called fluopyram (sold commercially as Broadform) that can be applied as a leaf spray. There aren’t yet published findings on its use to treat BLD, and one particular challenge has been determining the timing of application. This is because there are nematodes at overlapping life stages on an infected tree, and the chemical won’t necessarily reach nematodes that are inside buds. It’s also unclear whether it affects their eggs. Cowles suggests applying fluopyram just once in the spring, after young leaves have fully expanded. At that time, he says, the population of nematodes would be at its lowest and the tender leaves would absorb the chemical well, allowing it to kill the nematodes inside them. Another approach is to apply it later in the growing season when nematodes are migrating from the leaves to the buds (but ideally before they enter the buds). Some arborists recommend multiple applications during the growing season, though Cowles points out that there could be some risk of the nematodes developing resistance to the chemical.
European beech leaves infected with beech leaf disease. Symptoms can appear differently than in American beech. Credit: Heather Faubert
Another product, potassium phosphite, is known to boost plants’ own defenses, and early research by Cleveland Metroparks and Davey Tree Expert Company on 40 small trees (2-4 inches in diameter) over six years suggests that it can also protect against the effects of BLD. It can be applied a number of ways: soil wash, trunk injection, bark spray or leaf spray. Cowles says researchers have some insight into the mechanism at play based on how potassium phosphite works to protect wheat from a different nematode—it interferes with the nematodes’ ability to hijack the plant’s cell development. What’s still unclear is the best timing of application and ideal quantity to use for different sized trees, though Cowles and other scientists are conducting research on larger trees.
For homeowners looking to treat their infected trees, Brazee recommends contacting an arborist who has experience with BLD. Chemical regulations vary by state, he says, and chemical options may require a pesticide applicator’s license.
One last option: Simply keep trees as healthy as possible so they can try to resist the nematode on their own, Brazee says. This could mean creating a large mulch ring around the tree so that the roots aren’t competing with turfgrass or other plants; keeping the tree well watered; managing other pests and soil pH; and keeping the soil in optimal condition by providing it with organic matter and nutrients.
While he’s not optimistic that those measures alone will save most trees, Brazee says it’s something people are trying since it’s unclear how well the chemical options are working.
“We just need some more time to assess how the treated trees are faring on a year-to-year basis.”
Extent Of BLD As Of February 2023
A map showing the documented range of beech leaf disease as of February 2023. Colors indicate the year it was first observed in each county. Credit: Cleveland Metroparks
Robin Kazmier is Senior Editor, Digital. She writes and edits articles and helps shape Science Friday’s digital strategy. Her favorite bird is the squirrel cuckoo.
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CABI study unearths important lessons for the fight against fall armyworm
A study by CABI contributes important knowledge on fall armyworm (Spodoptera frugiperda). CABI’s research findings suggests that employing more sustainable and environmentally friendly solutions could help mitigate the damaging impacts of the species.
Published in CABI Agriculture and Bioscience, the article explores the economic impacts and management of fall armyworm in smallholder agriculture in Ghana, one of the many countries to have recently fallen victim to infestations of the pest. CABI’s teams collected survey data in two rounds (2018 and 2020) from 370 smallholder households in the major maize-growing areas of the country.
The study found that following the increased adoption of biopesticides and cultural practices for fall armyworm management, the maize yield losses in Ghana were not as severe as initially predicted.
Dr. Justice Tambo, lead author of the study and Senior Socio-Economist at CABI said:
“Unlike in the early years of the fall armyworm invasion, there has been reduced intensity of pesticide use and increased use of protective equipment (PPE) when spraying pesticides, and consequently less incidence of acute pesticide poisoning among maize farmers.”
These findings could have important implications for efforts to control the pest not only in Ghana, but also elsewhere.
The march of the fall armyworm
Native to the Americas, fall armyworm has spread like wildfire across parts of the globe. In 2016, there were only six countries in Africa with documented sightings of the pest. According to the FAO there are now around 80 countries in Africa, the Near East, Asia and the Pacific with cases of the species.
The voracious pest has an appetite for over 80 varieties of crops, but it prefers to feed mostly on maize. The larvae burrow into the crop’s stem and cob at various stages of its lifecycle, which renders the maize useless.
Maize is the world’s second most produced crop, after sugar cane, and the most farmed cereal grain by some margin. The crop is crucial to the economies of many African states. It is a staple food for an estimated 300 million Africans. Estimates suggest that, without remedial action, fall armyworm could reduce Africa’s maize supply by between 8.3 and 20.6 million tonnes per year.
Although fall armyworm is impossible to eradicate, it can be controlled. The most popular method for this is through the application of pesticides. But this approach has harmful effects on human and animal health. Using chemical pesticides also damages the environment and can deter natural enemies of fall armyworm .
Ghana’s maize economy and fall armyworm
First detected in Ghana in late 2016, fall armyworm quickly established itself as the dominant pest for the country’s maize. The crop accounts for over 50% of the nation’s total cereal production. A 2018 evidence note by CABI revealed that maize farmers had average losses of 26.6% in Ghana due to infestations.
When fall armyworm invasions first started, farmers opted to use pesticides as the most popular counter method. In 2017, Ghana allocated USD 4 million to procure and distribute pesticides as an emergency response to the invasive pest. Research from 2018 has documented how Ghanaian farmers’ failure to take preventive measures, such as using PPE, has had harmful impacts on their health.
A national multi-stakeholder task force was created and charged with advising Ghana’s Minister of Food and Agriculture and coordinating the response to fall armyworm. Authorities also launched public information campaigns to increase awareness of fall armyworm and promote sustainable management practices.
CABI’s researchers wanted to better understand if and how these measures had affected farmers’ behaviour. And gauge the economic impacts. The team collected survey data from farmers in 2018 and the same households were revisited in 2020.
Breakthrough findings
CABI’s scientists found that the rates of fall armyworm infestation in smallholder farmers’ fields were lower in 2020 than 2018. What’s more, smallholder farmers were resorting to IPM and agroecological approaches for combating fall armyworm, in line with recommended practices. There was greater adoption of preventive cultural measures, such as timely planting, regular weeding and fertilizer application. Plus, intercropping and rotation with non-host plants.
While farmers continued to use chemical pesticide, they applied it more sparingly. There was also an increase in the use of biopesticides. PPE items were also being used more frequently when spraying pesticides.
Worst-case scenario estimates made in 2017 suggested Ghana’s maize production could be reduced by 45%, equivalent to US$ 284.4 million in lost revenue, due to fall armyworm invasions. But findings from the survey data from 2017 and 2020 indicate that there was up to a 14% (statistically insignificant) reduction in maize yields for household experiencing fall armyworm infestations compared to those without. This suggests that initial forecasts may have been overestimated. The various actions taken to tackle fall armyworm in Ghana, and a build-up of natural enemies, may have led to this marked reduction in the economic losses incurred.
Towards more effective and sustainable approaches
As the problem of fall armyworm persists and cannot be eradicated, there is an urgent need to increase the promotion of sustainable and environmentally friendly solutions to mitigate its impacts. While using pesticides is still a popular approach among smallholder farmers across many parts of the world, it carries risks to human health and the natural enemies of the species. This means improving farmers’ knowledge of safe pesticide use practices will be crucial.
Incentivising the adoption of safer alternatives to synthetic pesticides, such as biopesticides and IPM could be an effective pathway for policymakers. Looking to the future, governments could invest in the development and promotion of resistant varieties of maize. Plus, biological control agents, which could help reduce the reliance on pesticides.
Read the study in full:
Tambo, J.A., Kansiime, M.K., Mugambi, I. et al. Economic impacts and management of fall armyworm (Spodoptera frugiperda) in smallholder agriculture: a panel data analysis for Ghana. CABI Agric Biosci4, 38 (2023). https://doi.org/10.1186/s43170-023-00181-3
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Pest warnings are changing the way that smallholders in Ghana farm. Smallholder maize farmers in Ghana have long grappled with the challenges posed by crop pests. Over the past few years, this has included the notorious fall armyworm. This voracious in…
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