How you can help Guam's dying gagu

Caused by bacterial wilt and wetwood bacteria, droplets of ooze often form in declining ironwood trees.

Editor’s note: This is the first in a two-part series about plant diseases on Guam and Micronesia.What happened to the huge, lush, towering, 100-year-plus gagu, or ironwood trees, that commonly dotted the island’s landscape at the University of Guam, Tiyan, Windward Hills Country Club golf course and elsewhere?

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Andersen Air Force Base’s Palm Tree Golf Course won an environmental innovation award for its handling of the coconut rhinoceros beetle.

Known by its scientific name Casuarina equisetifolia, ironwood trees are tightly integrated into Guam’s environment and local culture.

It is a hardy, pioneer, salt-resistant tree that occurs on the island’s main soil types: limestone, volcanic, and coral sand. It is propagated for windbreaks, erosion control, and urban landscapes.

Because C. equisetifolia is the dominant tree species on many of the sandy beaches of the Mariana Islands, it has become an important perching tree for the white-collared kingfisher (Halcyon chloris), the Mariana fruit-dove (Ptilinopus roseicapilla), and the white fairy tern (Gygis alba), which commonly lays eggs in the trees.

 There’s a fungus among us

It has been continually propagated since the 1600s. Due to its buoyant cones, it likely floated to Guam’s sandy beaches thousands of years ago on currents from the central Indo-Pacific coastline.From these cones, seeds were shed and grew into trees. Over time, ironwood became one of Guam’s prominent members of the halophytic (sea-salt adapted) vegetation type.Based on what we now know, Guam’s healthiest trees tend to occur in natural areas, near the coastline and in areas not prone to drought.Cocos Island and Ritidian are just a few of the places where healthy coastal stands of ironwood can still be found.

How you can help Guam's dying gagu

Huge, healthy ironwood trees still dominate the shoreline of Ritidian Point in northern Guam.

Farmer seeks help

In 2002, local grower Bernard Watson contacted University of Guam professor Robert Schlub about a group of five ironwood trees in one of his windbreaks that exhibited symptoms of rapid yellowing and death. Death occurred within a few weeks of symptom onset.This was totally unexpected because the trees in question were only 10 years old.Cross-sections of these trees exhibited areas of wetwood that were dark, water-infused, and radiated from their centers. Droplets of bacterial ooze appeared inside and outside the wetwood stained areas.Also appearing on Watson’s farm in 2002 were trees with the same cross-sectional symptoms but this time it was accompanied by thinning foliage and a much slower lethal decline.

 How to manage plant diseases

This latter condition was quickly discovered in other areas of Guam and was coined “ironwood tree decline” by Schlub and Zelalem Mersha, a former UOG post-doctoral fellow now working as a Virginia State University research and extension plant pathologist.Unraveling the cause or causes of IWTD would become a major focus of Schlub’s work at the University of Guam for the next two decades.In the course of the investigation, the Guam team would join forces with researchers from institutes in California, Georgia, Florida, Hawaii, Louisiana, South Africa, China and Australia.Many possible causes of IWTD have been eliminated by the team over the years.

Links to the disease

Age was ruled out as an IWTD contributor, when trees of varying ages began dying in areas where decline was most severe. The failure to find a correlation between the presence of beetles or nematodes (microscopic worms) ruled them out as causing IWTD.The normal appearance of tree buds and young foliage eliminated the likelihood of viruses being involved.Seeing no link between typhoon damage and decline in tree surveys in 2008 and 2009, Typhoons Paka in 1997 or Pongsona in 2002 were eliminated as causing Guam’s ‘sick’ trees.

 Plant diseases to watch for in the rainy season

Over time, five things were consistently linked to IWTD: The presence of termites on the side of trees. The occurrence of wood-rot fungi at the base of trees.The exposure of trees to harmful landscaping practices and the presence of bacterial ooze in tree cross-sections caused, namely the bacteria that causes wetwood and the bacteria that causes bacterial wilt.Bacterial wilt is caused by bacteria within the Ralstonia solanacearum species complex.

Trees decline in 13 years

We now know that Guam’s wilt pathogen strain is the same one that has been killing trees in China and India for decades.One of the team’s most recent projects included a resurvey of 200 trees that were part of a survey of 1,427 conducted in 2008-09. The project was funded by the McIntire-Stennis Cooperative Forestry Research Program (project GUA932, accession no. 1017908), under the U.S. Department of Agriculture’s National Institute of Food and Agriculture.The results suggest that the decline of Guam’s ironwood trees that began in 2002 is continuing to this day, and that trees with severe wilt symptoms or that are nearly dead have high bacterial wilt infection levels.From the data, it is reasonable to expect that half the trees that appear healthy today in areas of decline such as at the University of Guam campus or Fort Soledad will begin showing symptoms of decline over the next 13 years and that trees already suffering from IWTD will likely be dead or nearly dead within the same time period.

Foliage thinning is one of the ominous signs that this ironwood tree on the University of Guam campus is suffering from decline.

How you can help

Several steps have been taken to reduce the impact of IWTD.Hundreds of trees from various countries have been planted to add new genes to Guam’s tree population through cross-pollination.Some of these trees have been used to establish new ironwood windbreaks and others have been used as replacement trees in windbreaks with high levels of decline.Professionals and the general public are now being advised to reduce lawnmower and weed-trimmer damage to roots and the base of trees as a means to reduce infection and spread of fungi and bacteria.

To reduce transmission of Ralstonia and wetwood bacterial ooze when pruning, individuals are instructed to disinfect all tools.

How you can help Guam's dying gagu

Huge, healthy ironwood trees still dominate the shoreline of Ritidian Point in northern Guam.

The public is also being advised to remove severely declined trees as a means to protect nearby healthy trees.Planting healthy, young trees of different varieties or hosts is the quickest way to restore areas with high decline.

Robert L. Schlub is a plant pathology professor and extension specialist, and Elizabeth Hahn and Julia Delorm are extension associates with the Cooperative Extension Service at the University of Guam’s College of Natural and Applied Sciences.

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Open Letter on the crucial role of fungi in preserving and enhancing biodiversity

Latest news

Published on14.12.2022

Fungi

Biodiversity

When we think of forests we usually think of trees, plants and animals. But forests could not exist without fungi, which lie at the base of the biodiversity webs that support much of life on Earth.

Most fungi live as branching, fusing networks of tubular cells known as mycelium which can make up between a third and a half of the living mass of soils. Globally, the total length of fungal mycelium in the top 10cm of soil is more than 450 quadrillion km: about half the width of our galaxy. These networks comprise an ancient life-support system that easily qualifies as one of the wonders of the living world. Despite that, fungi represent a meagre 0.2% of our global conservation priorities.  

Fungi are largely invisible ecosystem engineers that have shaped life on Earth for more than a billion years. In fact, around 500 million years ago, fungi facilitated the movement of aquatic plants onto land, fungal mycelium serving as plant root systems for tens of millions of years until plants could evolve their own. This association transformed the planet and its atmosphere – the evolution of plant-fungal partnerships coincided with a 90% reduction in the level of atmospheric carbon dioxide. Today, most plants depend on mycorrhizal fungi – from the Greek words for fungus (mykes) and root (rhiza) – which weave themselves through roots, provide plants with crucial nutrients and defend them from disease.

Put simply, fungal networks embody the most basic principle of ecology: that symbiosis is fundamental to life on earth. Plants supply carbon to their fungal partners in exchange for nutrients like nitrogen and phosphorus – much of the phosphorus that makes up the DNA in your own body will have passed through a mycorrhizal fungus. In their exchange, plants and fungi engage in sophisticated trading strategies. The influence of these quadrillions of microscopic trading decisions spills out over whole continents. Globally, at least 5 billion tons of carbon dioxide are allocated from plants to mycorrhizal networks each year.

A call to action

A paradigmatic but often forgotten example of the keystone role of fungi is in the world’s forests, which are among the most important biological systems on our planet. They are our largest terrestrial carbon sink and the main terrestrial source of precipitation and oxygen. They house much of the planet’s biodiversity, serving as irreplaceable libraries of different ways to rise to the challenge of living.

However, current biodiversity, climate change, and sustainable food strategies, including forest restoration efforts overlook fungi and focus overwhelmingly on plants (flora) and animals (fauna). We urgently need to add a third “F” – funga – to create holistic conservation strategies that simultaneously address the triple planetary challenges of climate change, biodiversity loss and food security.  

Fungi must be incorporated into law-making and decision-making in international environmental treaties and frameworks, as well as national agricultural and environmental laws and policies, and local conservation and environmental initiatives. We invite the leaders meeting in COP 15 to start this process by adding fungi to the Post-2020 global biodiversity framework. Fungi have long sustained and enriched life on our planet. It’s time they receive the attention they deserve.

This open letter was written by:

Marc Palahí, Director European Forest Institute
Toby Kiers, Director Society for the Protection of Underground Networks
Merlin Sheldrake, author of Entangled Life
Giuliana Furci – Executive director, Fungi Foundation & co-chair IUCN SSC Fungal Conservation Committee
Robert Nasi, Chief Executive Officer, CIFOR-ICRAF
César Rodríguez-Garavito, Professor of Clinical Law and Director, Earth Rights Advocacy Clinic, New York University School of Law

Photo: Carolina Magnasco/Fungi Foundation

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DECEMBER 20, 2022

Researchers analyze performance of bacterium in combating coffee rust

by Ricardo Muniz, FAPESP

Researchers analyze performance of bacterium in combating coffee rust
The research is part basic science, investigating the bacterium’s resilience in a hostile environment—coffee leaves—and part biotech, seeing whether the bacterium inhibits the development of a pathogen. Credit: Jorge Mondego/IAC

A new study has analyzed the potential of a bacterium for biological control of the fungus Hemileia vastatrix, which causes coffee rust, a major challenge for Brazilian coffee growers. An article on the study is published in the journal BMC Microbiology.

The symptoms of coffee rust are yellow spots like burn marks on the leaves of the plant. The disease impairs photosynthesis, making foliage wither and preventing bean-producing cherries from growing until the tree resembles a skeleton. It is typically controlled by the use of copper-based pesticides, which can have adverse effects on the environment.

“This was a basic science study, in which we set out to understand the behavior of bacteria that inhabit the leaves of coffee trees. First of all, there are several compounds that are harmful to bacteria and can be used to attack them,” said Jorge Maurício Costa Mondego, last author of the article.

“Second, leaves are environments that undergo significant environmental pressures, such as sunlight and rain. We wanted to understand how bacteria that live on coffee leaves can withstand both the compounds produced by the coffee plant and the stresses of rain and sun,” he said.

Besides this basic science front, the study also addressed applied science challenges. The researchers decided to find out whether bacteria that inhabit coffee leaves can combat the fungus that causes coffee rust. The first step consisted of identifying the expressed sequence tags (ESTs) of Coffea arabica and C. canephora produced by the Brazilian Coffee Genome Project (Projeto Genoma EST-Café).

“I was the first author, alongside Ramon Vidal, a professor at UNICAMP, of an article in which we compiled the sequences expressed by C. arabica. It was published in 2011. We weren’t yet thinking in terms of metagenomics, but that’s what we did, more or less accidentally,” Mondego said.

Accidental metagenomics

The researchers found sequences they considered contaminating in the midst of the coffee leaf ESTs. “We took these sequences, fed them into the database, and concluded that they appeared to be from Pseudomonas spp, a genus of bacteria.,” Mondego said. “This stimulated the curiosity of our research group, which was led by Gonçalo Pereira, also a professor at UNICAMP. We asked ourselves, ‘What if we’ve done metagenomics without meaning to? Do these bacteria really live on coffee leaves?'”

At the time, Mondego was already a researcher at IAC. A few years later, he was able to join forces with Leandro Pio de Sousa, first author of the article published in BMC Microbiology. Sousa was a student who had a scientific initiation scholarship and now holds a Ph.D. in genetics and molecular biology from UNICAMP.

“I invited Leandro to work with me on this study, which was designed to see if Pseudomonas really does live on coffee leaves. If so, the previous findings would be confirmed. He agreed immediately,” Mondego said.

They isolated bacteria from the coffee leaves and put them in a culture medium. Under ultraviolet light, it is possible to characterize Pseudomonas, which looks purple and can easily be selected in the medium. “We collected the bacteria, extracted their DNA and sequenced one, which we called MN1F,” he said.

They made several interesting discoveries about MN1F, which has a secretion system that reflects its need to survive in a hostile environment full of fungi and other bacteria. “The secretion system produces antibacterial and antifungal compounds. That suggested it could be used for biological control,” Mondego said. They also detected a number of proteins associated with protection against water stress.

The next step entailed physiological experiments, whereby bacteria were cultured in different media to confirm the researchers’ observations regarding the genome. “The biological experiments proved several inferences correct. We showed that the bacterium does indeed have a considerable capacity to withstand strong osmotic pressure, which can be considered analogous to the effects of drought on coffee leaves,” Mondego explained. “Furthermore, MN1F is capable of degrading phenolic compounds that can be harmful to it. It breaks down these compounds from the plant and converts them into material for its own survival.”

The researchers then conducted a battery of tests to find out if MN1F could be used for biological control, preventing or inhibiting the development of H. vastatrix, the fungus that causes coffee rust. The tests took place under greenhouse and laboratory conditions, including an attempt to inhibit in vitro germination of the fungus. In all of the experiments, the bacterium proved capable of inhibiting the development of spores (reproductive units) and mycelium (the filamentous network containing the fungus’s genetic material).

More information: Leandro Pio de Sousa et al, Functional genomics analysis of a phyllospheric Pseudomonas spp with potential for biological control against coffee rust, BMC Microbiology (2022). DOI: 10.1186/s12866-022-02637-4

Journal information: BMC Microbiology 

Provided by FAPESP 


Explore further

Fungus that eats fungus could help coffee farmers

Virus Undercuts Fungus’s Attacks on Wheat

USDA Agricultural Research Service sent this bulletin at 11/29/2022 10:05 AM EST

View as a webpageARS News ServiceARS News
ServiceFusarium head blight on wheat
A “mycovirus” could help stop the Fusarium head blight fungus from contaminating wheat grains and giving them a ghastly bleached appearance (shown at right).Virus Undercuts Fungus’s Attacks on Wheat
For media inquiries contact: Jan Suszkiw, (202) 734-1176

November 29, 2022 A naturally occurring virus co-discovered by Agricultural Research Service (ARS) and university scientists may offer a way to undermine a costly fungal threat to wheat, barley and other small-grain crops.The fungus, Fusarium graminearum, is the chief culprit behind a disease called Fusarium head blight, or “scab.” Unchecked with fungicides or other measures, scab diminishes the yield and quality of the crops’ grain. Under wet, humid conditions, the scab fungus can release a toxin called deoxynivalenol (a.k.a., “vomitoxin”) that can contaminate the grain, reducing its point-of-sale value or leading to outright rejection depending on end use.Now, however, a team of scientists with the ARS Application Technology Research Unit in Wooster, Ohio, and South Dakota State University in Brookings (SDSU) has discovered a strain of a fungal virus, or “mycovirus,” that disables the scab fungus’s vomitoxin-making machinery.In nature, the mycovirus, a species called Fusarium graminearaum Vg1, infects the scab fungus to replicate and spread. But the new mycovirus strain, dubbed F. graminearum Vg1-SD4, takes such attacks a step further by stopping the scab fungus from making vomitoxin—a fortuitous benefit for wheat plants.Indeed, in laboratory and greenhouse experiments, cultures of the scab fungus that had been infected with the mycovirus strain grew slower than non-infected cultures and produced no vomitoxin in the grain of susceptible potted wheat plants. In contrast, the grain of wheat plants exposed to mycovirus-free cultures of scab contained 18 ppm of vomitoxin, a byproduct of the fungus’s metabolism that can be harmful to livestock and human health.ARS molecular biologist Shin-Yi Lee Marzano and her collaborators discovered the mycovirus strain after sequencing its genomic makeup and noticing slight differences from its “parent” species, FgVg1, which had been maintained in a live culture of the scab fungus and known to science for about a decade.Marzano cautioned that their research—reported in the July 2022 issue of Microorganisms—is still in its early stages. However, with further study, the mycovirus strain could prove useful as a biological control agent that could be formulated and sprayed onto susceptible wheat varieties or other small-grain crops. That, in turn, could potentially offer growers another tool to use in avoiding costly losses to scab and its contamination of grain destined for livestock and human consumption.  Marzano collaborated on the mycovirus strain research with Bimal Paudel and Yang Yen—both with SDSU’s Department of Biology and Microbiology—and Connar Pedersen (formerly SDSU and now ARS).The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.Interested in reading more about ARS research? Visit our news archiveU.S. DEPARTMENT OF AGRICULTURE
Agricultural Research Service

The correct identification of insect pests and their natural enemies is critical for developing sound and sustainable pest management strategies: this is particularly so for rice. In the 1960’s, a comprehensive rice insect pest and natural enemy collection was established at the International Rice Research Institute (IRRI) in the Philippines, with the aim of helping those in national rice research programs to identify rice arthropods. 

A similar project was begun in West Africa in 1990, establishing a rice insect and natural enemy collection at WARDA (West African Rice Development Association), which subsequently became AfricaRice.

Associated with both of these collections, dichotomous keys were developed and published in the following books on rice arthropods:
Biology and Management of Rice Insects,
edited by E. A. Heinrichs (1994) and published by IRRI, and 
Rice Feeding Insects and Selected Natural Enemies in West Africa, authored by E. A. Heinrichs and Alberto Barrion (2002).

While the printed versions of both books have been out-of-print for several years, a recent upgrade of the Lucid software program, which makes it possible to convert paper-based, dichotomous keys to interactive pathway keys, means that both keys are now freely available to use on the Internet, courtesy of IAPPS (International Association for the Plant Protection Scientists) at: http://www.plantprotection.org

 Adding arthropod images: Note that the IRRI key now includes a large number of color images of important insect pests and natural enemies. E.A. Heinrichs (eheinrichs2@unl.edu) would appreciate any good resolution images that colleagues would be willing to submit for adding to the key – with due acknowledgement

IRRI arthropod key

West African arthropod key

© Copyright International Association for the Plant Protection Sciences. All rights reserved 2022.