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.


Welcome to the discussion.

DECEMBER 6, 2022

Tracking an invasion: A single Asian hornet may have sparked the ongoing spread across Europe

by Pensoft Publishers

Tracking an invasion – a single Asian hornet sparked the ongoing spread across Europe
The Asian Hornet specimen recovered in Dublin. Credit: Dr Aidan O’Hanlon

In Europe, the Asian (or “Yellow-legged”) Hornet (Vespa velutina) is a predator of insects such as honeybees, hoverflies, and other wasps, and poses serious risks to apiculture, biodiversity and pollination services. This hornet can measure up to 4 cm in length and, like all other social wasps, is capable of delivering a painful sting, although it is not aggressive by nature.

Thought to have been introduced into Europe from China in 2004, the Asian Hornet has rapidly spread across the continent. While it has been thus far controlled in Britain, the hornet is well established across mainland Europe and the Channel Islands. In April 2021, the Irish National Parks and Wildlife Service confirmed that a single specimen had been found, “alive but dying” in a private dwelling in Dublin, marking the first Irish record of this species.

The circumstances of how the specimen arrived in the Irish capital are not known, but with the area’s extensive regional, national and international connectivity, there can be many possible pathways of introduction. In an Irish context, it was of particular interest to determine whether this individual originated in Europe/Britain or represented a potential new invasion source from within its native range in Southeast Asia.

The specimen was deposited in the National Museum of Ireland and identified by Dr. Aidan O’Hanlon, who suggested performing genetic analysis to determine its provenance.

In collaboration with scientists from the School of Biological, Earth and Environmental Sciences (BEES), University College Cork, and partners on the EU Atlantic Positive Project (which aims to establish Europe-wide methodologies for the control of the Asian hornet), genetic analysis was performed and data were compared with those from specimens provided from several other locations across Europe. The researchers then published their findings in Journal of Hymenoptera Research.

“Earlier work had demonstrated that Asian hornets in Europe apparently shared the same genetic lineage, based on studies of a single gene. We took this a step further and looked at two additional genes which would be more sensitive in detecting variation within the invasive population,” explains Dr. Eileen Dillane of BEES.

Data from all three genetic markers confirmed that not only are Asian hornets in Europe of a single pedigree, but are likely descended from a single mated queen hornet that somehow arrived in France in 2004. Furthermore, this lineage has not yet been described within the native range.

“Our research has revealed the remarkable potential for population expansion of eusocial insects in invaded areas, even when original genetic diversity is extremely low,” says Dr. Simon Harrison, who is part of the research team .

These findings are both bad news and good news for the control of the Asian hornet in Europe. While single mated queens can evidently rapidly re-colonize areas from where hornets have been eradicated (for example, where intensive efforts have destroyed all nests in an area), the close relatedness of all individuals of the Asian hornet in Europe offers hope for eradication methods based on biological control.

In the Irish context, it is unlikely that this is the beginning of a larger-scale invasion, as the climate and habitat landscape of Ireland is likely less than ideal for the Asian hornet, which requires higher summer temperatures and a greater supply of energy-rich food. “Nonetheless, climate change is likely to increase the threat of a successful invasion in the future, so vigilance against this species must be maintained,” the authors of the study advise.

More information: Eileen Dillane et al, The first recorded occurrence of the Asian hornet (Vespa velutina) in Ireland, genetic evidence for a continued single invasion across Europe, Journal of Hymenoptera Research (2022). DOI: 10.3897/jhr.93.91209

Journal information: Journal of Hymenoptera Research 

Provided by Pensoft Publishers 

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Friday, 09 December 2022 07:05:00

Grahame Jackson posted a new submission ‘PINK DISEASE, CITRUS – PAPUA NEW GUINEA: (EASTERN HIGHLANDS)’



ProMED Source: PNG Post-Courier [summ. Mod.DHA, edited]

Pink disease is ravaging citrus trees in the country. A citrus grower with 300 trees said if nothing is done about it, the disease will wipe out the citrus trees in the country. He said it is widespread in Eastern Highlands province and has been there for a long time, but no one has been doing anything about it. Citrus varieties such as mandarin, oranges, lemons, and lime are grown there. Many growers are neglecting their orchards because of diminishing returns and difficulties in management. The industry is now decimated by pink disease, and serious intervention is needed to save the trees from the devastating disease.

Although the Fresh Produce Development Agency (FPDA) may have some funds available for citrus, small growers to date have not received any word or support from them or any other key agencies within the agriculture sector. The Highlands Farmers Settlers Association said the disease raises a series of concerns that have not been addressed by relevant government agencies. FPDA or other relevant agencies have not commented so far.

[Byline: Lorraine Wohi]

Communicated by:

[Pink disease of citrus is caused by the fungus _Necator salmonicolor_ (previously _Erythricium salmonicolor_). The pathogen also affects a range of other woody hosts, including tree crops (e.g., quince, custard apple, apple), but has also been found on herbaceous hosts such as capsicum. Several fungal groups have been identified in different locations and host species. Pathogen development is favoured by warm temperatures and high humidity, resulting in crop losses mainly for subtropical and tropical environments.

Symptoms on citrus may include wilting of twigs and leaves; die-back of branches; necrosis of leaves and bark; pinkish-white mycelium on affected branches; and longitudinal cracking and gumming on branches. Forest trees may serve as pathogen reservoirs for crops. Disease incidence is higher in densely planted groves due to increased air humidity. Spread can occur by air currents and with contaminated plant or other materials. Disease management may include plant hygiene measures (e.g., removal and burning of infected wood) and fungicide (e.g., copper) sprays.

Papua New Guinea: (with provinces)

Pink disease on citrus:×1024/5582334.jpg,

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Climate change means farmers in West Africa need more ways to combat pests

by Loko Yêyinou Laura Estelle, The Conversation

worm on corn
Credit: Unsplash/CC0 Public Domain

The link between climate change and the spread of crop pests has been established by research and evidence.

Farmers are noticing the link themselves, alongside higher temperatures and greater variability in rainfall. All these changes are having an impact on harvests across Africa.

Changing conditions sometimes allow insects and diseases to spread and thrive in new places. The threat is greatest when there are no natural predators to keep pests in check, and when human control strategies are limited to the use of unsuitable synthetic insecticides.

Invasive pests can take hold in a new environment and cause very costly damage before national authorities and researchers are able to devise and fund ways to protect crops, harvests and livelihoods.

Early research into biological control methods (use of other organisms to control pests) shows promise for safeguarding harvests and food security. Rapid climate change, however, means researchers are racing against time to develop the full range of tools needed for a growing threat.

The most notable of recent invasive pests to arrive in Africa was the fall armyworm, which spread to the continent from the Americas in 2016.

Since then, 78 countries have reported the caterpillar, which attacks a range of crops including staples like maize and has caused an estimated US$9.4 billion in losses a year.

African farmers are still struggling to contain the larger grain borer, or Prostephanus truncatus Horn, which reached the continent in the 1970s. It can destroy up to 40% of stored maize in just four months. In Benin, it is a particular threat to cassava chips, and can cause losses of up to 50% in three months.

It’s expected that the larger grain borer will continue to spread as climatic conditions become more favorable. African countries urgently need more support and research into different control strategies, including the use of natural enemies, varietal resistance and biopesticides.

My research work is at the interface between plants, insects and genetics. It’s intended to contribute to more productive agriculture that respects the environment and human health by controlling insect pests with innovative biological methods.

For example, we have demonstrated that a species of insect called Alloeocranum biannulipes Montr. and Sign. eats some crop pests. Certain kinds of fungi (Metarhizium anisopliae and Beauveria bassiana), too, can kill these pests. They are potential biological control agents of the larger grain borer and other pests.

Improved pest control is especially important for women farmers, who make up a significant share of the agricultural workforce.

In Benin, for example, around 70% of production is carried out by women, yet high rates of illiteracy mean many are unable to read the labels of synthetic pesticides.

This can result in misuse or overuse of chemical crop protection products, which poses a risk to the health of the farmers applying the product and a risk of environmental pollution.

Moreover, the unsuitable and intensive use of synthetic insecticides could lead to the development of insecticide resistance and a proliferation of resistant insects.

Biological alternatives to the rescue

Various studies have shown that the use of the following biological alternatives would not only benefit food security but would also help farmers who have limited formal education:

  1. Natural predators like other insects can be effective in controlling pests. For example I found that the predator Alloeocranum biannulipes Montr. and Sign. is an effective biological control agent against a beetle called Dinoderus porcellus Lesne in stored yam chips and the larger grain borer in stored cassava chips. Under farm storage conditions, the release of this predator in infested yam chips significantly reduced the numbers of pests and the weight loss. In Benin, yams are a staple food and important cash crop. The tubers are dried into chips to prevent them from rotting.
  2. Strains of fungi such as Metarhizium anisopliae and Beauveria bassiana also showed their effectiveness as biological control agents against some pests. For example, isolate Bb115 of B. bassiana significantly reduced D. porcellus populations and weight loss of yam chips. The fungus also had an effect on the survival of an insect species, Helicoverpa armigera (Hübner), known as the cotton bollworm. It did this by invading the tissues of crop plants that the insect larva eats. The larvae then ate less of those plants.
  3. The use of botanical extracts and powdered plant parts is another biological alternative to the use of harmful synthetic pesticides. For example, I found that botanical extracts of plants grown in Benin, Bridelia ferruginea, Blighia sapida and Khaya senegalensis, have insecticidal, repellent and antifeedant activities against D. porcellus and can also be used in powder form to protect yam chips.
  4. My research also found that essential oils of certain leaves can be used as a natural way to stop D. porcellus feeding on yam chips.
  5. I’ve done research on varietal (genetic) resistance too and found five varieties of yam (Gaboubaba, Boniwouré, Alahina, Yakanougo and Wonmangou) were resistant to the D. porcellus beetle.

Next generation tools

To develop efficient integrated pest management strategies, researchers need support and funding. They need to test these potential biocontrol methods and their combinations with other eco-friendly methods in farm conditions.

Investing in further research would help to bolster the African Union’s 2021–2030 Strategy for Managing Invasive Species, and protect farmers, countries and economies from more devastating losses as climate change brings new threats.

Initiatives like the One Planet Fellowship, coordinated by African Women in Agricultural Research and Development, have helped further the research and leadership of early-career scientists in this area, where climate and gender overlap.

But much more is needed to unlock the full expertise of women and men across the continent to equip farmers with next generation tools for next generation threats.

Provided by The Conversation 

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Why African farmers should balance pesticides with other control methods

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Growers can use a test kit to detect ToBRFV before plants even shows signs

Knowing, for sure, that your crop is infected before the plants show signs. Growers have wanted that since the Tomato brown rugose fruit virus (TOBRFV) reared its ugly head. And preferably quickly, too. This summer, the Dutch company Spark Radar launched a grower test kit for that. Growers can use it to detect, with high reliability and within three hours, whether their crop is contaminated.

According to Spark Rader’s co-founder, Rogier van der Voort, its virus test’s reliability and sensitivity can well well-compared to that of a PCR test. “However, you don’t have to send our test’s samples to a service lab. That saves considerable time – crucial when detecting and containing a possible outbreak.”

When the COVID-19 pandemic broke out, he and Bas Rutjens, who founded Spark Genetics, put their heads together. That company has been supporting breeding companies with genetics issues since 2018. “When the pandemic began, the laboratory had to partially close. We started asking ourselves how we could offer the market something that was much needed. That had to be a reliable, sensitive pathogen test that anyone could perform on-site,” says Rogier.

Testing before symptoms show
The test works pre-symptomatically, meaning you can test for the virus’ presence early. Rogier draws a parallel with COVID-19. “You can now do a self-test for that. But, that’s an antigen test you use when you’re already showing symptoms.” In the case of the coronavirus, for example, a runny nose.

One of the ToBRFV’s symptoms is spots on the fruit or signs on leaves. “Antigen tests, however, aren’t as reliable as PCR tests, and their lower sensitivity means they don’t work pre-symptomatically. You can also only test two to three plants at once,” Rogier explains.

Leaf material
Currently, growers can test 60 plants at a time using Spark Radar test kits. Testing can be done in three ways. “We started with leaf samples. A piece of leaf the size of a fingernail is enough. Growers collect the leaf sample in a bag we provide, and once collected, testing can begin.”

The test kits include the test material and hardware so that growers can run the tests themselves. “We’ve developed equipment to read the tests. We use magnetic and sensing racks for that. The magnetic rack lets us extract the virus from the sample, which helps ensure our tests’ high sensitivity,” Van der Voort continues.

A part of the test kit. The white container is lined with magnets. Detection is done using a different rack.

Surface and water tests
Growers, however, prefer to test more than just leaf material. “There’s plenty of market demand for swab tests too, which allows for testing for the presence of the virus on things like carts or blades. It’s like the cotton swab you use in your throat and nose when doing a COVID-19 self-test.”

They developed a third testing protocol for water. “Growers can test for the ToBRFV in, say, their drainage system,” Rogier elaborates. These last two testing methods are currently in their final market introduction stages. “We’re fully in the testing phase for these new applications and are using trial feedback to make the swab and water test kits are durable as possible.” The company plans to market these two testing kits in December commercially.

Spark Radar also wants to start offering the kits internationally, and this fledgling company has taken the first steps toward that. “A large North American party has been using our test for several months. They want to deploy it more widely during the next harvest period. We have a commitment from a Dutch party with overseas farms too. They want to use our tests outside the Netherlands,” states Rogier.

A virus test must be reliable. The test kits, thus, include a clear manual (you can also watch an online video). For now, it is in Dutch and English, but the company wants to include other languages as well. “We’re currently focusing on producing the tests. We’ve gained new clients after presenting the test at a recent event.”

Testing for other pathogens
ToBRFV is undoubtedly receiving global attention. That begs the question: Does Spark Radar have the clout to help growers combat this virus? Spark Radar’s co-founder thinks so. “We were recently chosen to participate in the Foodvalley and government investment fund, InvestNL’s Fast Lane program. We had to give an answer to what’s needed to become even more influential, scale up and maintain our test’s current and projected speed.”

That speed does not only apply to the ToBRFV but to other plant viruses, bacteria, and fungi. Spark Radar is also working on a test kit for cucumber fur virus and Pepino mosaic virus in tomatoes. “Those will be similar tests to the ToBRFV ones,” concludes Rogier.

For more information:
Rogier van der Voort
Spark Radar
8 Padualaan
3584 CH, Utrecht, NL

Publication date: Fri 25 Nov 2022

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