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Fourteen years after being first detected in Sri Lanka, over 340,000 coconut palms identified as diseased, over 313,000 coconut palms cut down and destroyed, and billions of rupees spent on disease control, coconut growers in the Southern Province continue to be plagued by the Weligama Coconut Leaf Wilt Disease (WCLWD)
Coconut Research Institute (CRI) Deputy Director (Research) Dr. Nayani Arachchige said that the CRI together with Coconut Cultivation Board (CCB) and other related stakeholders including law enforcement authorities have managed to contain the disease to the Southern Province and added that if the coconut growers and the community on the whole had been more cooperative, the disease could have been controlled sooner.
The Weligama Coconut leaf Wilt disease is caused by phytoplasmas and transmitted by infective insect vectors, vegetative propagation or grafting of infected planting material to healthy plants, by vascular connections made between infected and uninfected host plants by parasitic plants, and by seed or embryo transmission. Once infected, a coconut palm will die within two years. There is no known cure and cutting down infected trees and incinerating the crowns is the only practical solution to arrest the spread of the disease.
Dr. Arachchige said that at the initial stage of infection, a coconut tree would bear profusely and growers have second thoughts of cutting down the tree even after they have been noticed to do so by the authorities. The delay causes greater harm as more trees in the vicinity are prone to infection and was one reason that containing the disease has taken so long.
The WCLWD was first detected in the Weligama area in 2008, but had spread from Galle to Tangalle. To prevent the disease spreading further, the CRI demarcated a buffer zone three kilometres wide on either side of the A17 trunk road from Galle running through Angulugaha, Henegama, Akuressa, Kamburupitiya, Kirinda – Puhulwella, Hakmana, Walsmulla, Beliatta and ending in Tangalle.
The Government, by gazette notification No. 1542/7 of 24 March 2008, prohibited the transport of any palm species and their live parts out of the demarcated boundary. Although the prohibition was not strictly adhered to due to various restraints, it was fortunate that the disease did not spread to other coconut growing areas.
The Matara district where WCLWD was first detected has borne the brunt of the disease. Figures obtained from the Coconut Cultivation Board show that up to September 30, 2022, 313,857 diseased trees have been identified in the Matara district.
Growers who complied with the order given by the CCB authorities and cut down the diseased trees were paid Rupees 3,000 per tree more as an initiative to cut and destroy the tree rather than compensation as the cost incurred by a grower to tend to a plant until it starts bearing and the loss of produce is very much more.
Due to WCLWD and other factors such as eating of the coconut by Grizzled Giant Squirrels and the Toque macaque, the annual yield in the Matara district had dropped from 121 million nuts in 2011 to 96 million nuts in 2019 and to 73 million nuts in 2020.
Some growers have been compelled to destroy their whole plantation and plant alternate crops as provisions of the Plant Protection Act prohibits planting any type of palm trees in the areas where WCLWD has been detected.
According to the CCB, WCLWD could be fully eradicated in the near future if the growers and public were more cooperative and if the Government would continue to provide adequate funds.
1of5Illinois State Entomologist Christopher Dietrich (top) joined efforts with ecology and evolutionary biology researcher Valeria Trivellone (right) and Yanghui Cao.Fred Zwicky/University of Illinois News
Phytoplasmas are bacteria that can invade the vascular tissues of plants, causing many different crop diseases.
While most studies of phytoplasmas begin by examining plants showing disease symptoms, a new analysis focuses on the tiny insects that carry the infectious bacteria from plant to plant. By extracting and testing DNA from archival leafhopper specimens collected in natural areas, the study identified new phytoplasma strains and found new associations between leafhoppers and phytoplasmas known to harm crop plants.
Reported in the journal Biology, the study is the first to look for phytoplasmas in insects from natural areas, said Illinois Natural History Survey postdoctoral researcher Valeria Trivellone, who led the research with INHS State Entomologist Christopher Dietrich. It also is the first to use a variety of molecular approaches to detect and identify phytoplasmas in leafhoppers.
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“We compared traditional molecular techniques with next-generation sequencing approaches, and we found that the newer techniques outperformed the traditional ones,” Trivellone said. These methods will allow researchers to target more regions of the phytoplasma genomes to get a clearer picture of the different bacterial strains and how they damage plants, she said.
“One thing that is really novel about this study is that we’ve focused on the vectors of disease, on the leafhoppers, and not on the plants,” Dietrich said. The standard approach of looking for phytoplasmas in plants is much more labor-intensive, requiring that scientists extract the DNA from a plant that appears to be diseased and checking for phytoplasmas, he said.
“But even when you identify the phytoplasma, you don’t know what leafhopper or other vector transmitted it to the plant,” Dietrich said. “So researchers must go back out into the field to collect all potential insect vectors. Then they do transmission experiments, where they let the leafhoppers feed on an infected plant and then put them on an uninfected plant to see if it catches the disease.”
Because this research is laborious and slow, “we still don’t have a good idea of which insects are spreading most phytoplasmas between plants,” Dietrich said. “That really limits your ability to set up an effective management strategy.”
For the new study, the researchers turned to leafhopper specimens in the INHS insect collection. Dietrich had collected many of these insects over a period of 25 years as part of his work classifying their genetic relatedness and evolution. The researchers examined 407 leafhopper species collected around the world in areas less disturbed by human development. The specimens came from North and South America, Africa, Europe, Asia and Australia.
The team extracted total DNA from the specimens and processed each one, using both traditional and newer sequencing approaches. The latter are less costly and more informative than traditional methods, the researchers report. Of the insects sampled, 41 tested positive for phytoplasmas, and the researchers obtained usable phytoplasma sequence data from 23 leafhoppers. The phytoplasmas included those that cause a disease known as aster yellows, which inhibits photosynthesis and reduces the productivity of several different crop plants. These phytoplasmas were found in several new species of leafhoppers never before identified as vectors of the disease.
“These leafhoppers may transmit the phytoplasmas to wild plants in natural areas,” Trivellone said.
The study found phytoplasmas in regions of the world where such diseases had not been reported and identified several new strains of bacteria. It also found previously unreported associations between some phytoplasmas and species of leafhopper.
Scientists have no tools to target the bacteria in asymptomatic plants to prevent disease outbreaks, so controlling phytoplasmas involves the use of pesticides to kill the insect vectors.
“Because the insecticides are only partially specific to the target insects, they kill a variety of beneficial insects as well, which is not sustainable,” Trivellone said.
“We’re finding that there are lots of new phytoplasmas out there in nature that nobody’s ever seen before,” Dietrich said. “They don’t cause disease symptoms in the native plants they’ve associated with for maybe millions of years. They only start causing disease when they jump to a new host that has not been exposed to the phytoplasma before.”
The new findings parallel those seen in emerging infectious diseases of humans originating in wildlife, Dietrich said. “This is why we need to look more broadly across nature and see what’s out there.”
Soil Health and Pest Management: Challenges in the European Union
CERTIS
05/07/2022
Jackie Pucci of AgriBusiness Global sat down with Dr. Arben Myrta, Corporate Development Manager with Certis Belchim B.V., based in Italy, to discuss developments in soil health and pest management solutions at the company and wider trends he is witnessing in the space.
Dr Arben Myrta, Certis Belchim B.V.Quality produce with good soil pest managementDamage by Fusarium wilt in melonDestroyed tomato plants from the attack of Meloidogyne spp.Damaged roots of tomato by the nematode Meloidogyne spp.Nematode damage in carrots from Meloidogyne spp.
Can you talk about some of the key developments in ‘soil health management’ in agriculture and what is driving adoption in Europe?
Soil health in its broad scientific definition considers its capacity, thanks to biotic and abiotic components, to function as a vital living ecosystem to sustain plants and animals. A soil may be healthy in terms of the functioning of its eco-system but not necessarily for crop production. In agriculture, good soil pest management remains a cornerstone for the quantity and quality of production at farm level. When farmers cultivate the same plants for a long time in the same soil without crop rotations or other agronomic measures, the soil starts to evidence nutritional and phytopathological problems for the plants. This is more evident in horticulture, and particularly, in protected crops in Europe, where this problem is of major importance.
In the past, in Europe, soil pest management in horticulture was mostly covered by chemical fumigation, lead first by methyl bromide (MB). MB was later globally banned for depleting the ozone layer, while other fumigants, which were intended to replace it, were not approved during the regulatory renewal process, thus creating a gap between the farmers’ needs and the possibilities to have adequate solutions for their cropping. Meanwhile, in the last decades there has also been huge progress in research and technology, developing more effective biorational soil products (beneficial microorganisms, such as fungi, bacteria, etc.., plant extracts, etc..) and increased public awareness around human health and the environment, followed by more restrictive legislation on the use of chemicals in agriculture.
Driven by the legislation and the general attention of society on the use of plant protection products in agriculture, the industry has been proactive in looking for new solutions with safer tox and eco-tox profile, focusing on biorational products, whose number, as new plant protection products for the control of soil-borne pests and diseases, is continuously increasing in the EU.
How important do you see soil health and soil pest management in the complete picture of agricultural productivity, and how has that view changed?
Soil health and good soil pest management practices in crop production have always been considered important. In Europe, the level of attention and knowledge on this topic has been higher among professionals and farmers working in horticulture, the ornamentals industry, nurseries and particularly protected crops, basically everywhere where long crop rotations are not easily practiced, and pest-infested soils become a big problem for the farmers.
The rapid banning or limitation of several traditional synthetic products used to control soil pests raised the question for field advisors and farmers of how to deal with soil problems in the new situation. In recent years European farmers have been facing particular difficulties in controlling plant-parasitic nematodes.
Biorational products available today in EU countries represent a very good tool for the management of several soil pests in many crops and targets, but are still not sufficiently effective to guarantee full satisfaction to the growers in important crops like protected fruiting vegetables, strawberry, carrots, potato, ornamentals, etc., which explains why ‘emergency uses’ are still granted at EU country level following the request of grower associations to cover the needs of their farmers. The continuous increase in the numbers of new biorational products in the future, and particularly the innovative formulations that will follow, will be of paramount importance for their role in soil pest management.
A second, but important obstacle, is the generally limited knowledge on soil components (including its fertility and capacity to suppress pests by beneficial microorganisms) and the correct use of the biorational products, which cannot be expected to be effective quickly or be used as solo products, as the ‘old’ chemicals were. They should be seen more in programs with other soil management solutions, as recommended by the integrated production guidelines. Here, a further important obstacle is the lack of an effective public extension service to advise farmers, which is limited or totally lacking in many European Countries.
Everybody in the EU is now convinced that soil management in the future will rely on biorational and integrated solutions, but the question is how to reach this objective gradually, being pragmatic and reliable, balancing the environmental, economic and agricultural perspective. Legislation always steers the direction of progress but should be carefully considering the real product capabilities to make it happen in a short time and not focusing on ‘emergency situations’ as has now been the case for more than a decade.
What are some of the perceptions, either correct or incorrect, and other challenges you are dealing with in the region with respect to products for soil health?
This market has seen a rapid change from chemistry to biorational solutions, but in the meantime is facing a lot of challenges in order to meet the expectations of the farmers for quantity and quality of produce. This topic is widely discussed in dedicated scientific forums like that of the International Society of Horticultural Sciences, of which the last International Symposium on Soil and Substrate Disinfestation was held in 2018 in Crete, Greece. A dedicated round table was organized with soil experts to discuss the important challenges faced by the European growers due to the lack of plant protection solutions for an effective control of several soil pests, most of all nematodes. I participated in that round table discussion, whose main conclusions were the following concerns, considered as target actions for the scientific community:
the farmer needs various tools for soil disinfestation (SD) in the light of the limited current arsenal of SD tools;
the lengthy and unpredictable European registration process (sometimes more than 10 years from dossier submission to the first national approval) of new plant protection products (including biorational) and the cautious approach of EU regulation, as well as restrictions imposed, has led to a reduction of active ingredients available in the past years;
a more effective and faster evaluation system is needed, especially for naturally occurring and low risk products (biological, plant extracts, etc.). That is, all products which are essential for Integrated Pest Management (IPM) programs;
following the implementation of Regulation EC 1107/2009, the only tool available to fill the gaps in local production systems is Art. 53 of the above-mentioned Regulation, which provides “derogations” for exceptional authorizations of plant protection products. Such authorizations increased exponentially in the last years, indicating that existing solutions in the European market are not considered sufficient;
the above-mentioned EU Regulation has a high socio-economic impact on various production systems in Europe and a Spanish case shows clearly the importance of maintaining a sustainable agricultural activity in local communities that, in the case of protected crops area, includes 13% of the active population employed in agriculture;
several European agricultural sectors are affected as the EU authority is allowing increased importation from extra-EU countries, considered unfair competition due to their more flexible registration system for plant protection products than that of the EU;
reduced capacity of soil pest research, where experts are retired and not being replaced, alongside weak, or in many areas non-existent, extension services together are causing the loss of soil knowledge and good advice for our farmers. Today, soil diagnosis is frequently completely lacking or insufficient before any soil pest and crop management decisions are taken.
The clear message from the scientific experts at that meeting was that these issues must be correctly addressed at all levels of stakeholders, in such a way that all available tools, including sustainable use of soil disinfestation, may be used in a combined IPM system to allow sustainable production in Europe.
What are some of the most exciting developments at Certis Belchim in soil health and pest management?
Since the establishment of Certis Europe in 2001, we have focused on soil pest and disease management. In 2003, Certis built the first CleanStart program providing integrated solutions for sustainable soil management, combining cultural, biological and chemical approaches. After more than a decade, in the mid-2010s, the CleanStart integrated approach started combining biological and chemical inputs with agronomic services (training to farmers and field advisors, soil pest diagnosis support for partner farms and stewardship product advice for applicators and/or farmers) to provide sustainable soil management for the future, aligned with the principles of the Sustainable Use of pesticides as per the EU Directive. All these activities were carried out successfully thanks to a wide international network created with many research institutes across Europe on soil pest management topics. This approach facilitated our participation in soil research projects funded also by the EU. Thanks to this experience we have been able to prepare and share many publications and communications, in particular the coordination for several years of an International Newsletter on Soil Pest Management (CleanStart).
Last year we were also granted a SMART Expertise funding from the Welsh Government, which is co-founded by Certis, in a research project lead by Swansea University, with Certis Belchim B.V. the industry partner, alongside major Welsh growers, Maelor Forest Nurseries Ltd and Puffin Produce Ltd. This project, now ongoing, looks to develop new and innovative products to control soil pests, primarily nematodes.
Thanks to this team involvement on soil topics, our present soil portfolio includes several biorational solutions such as Trichoderma spp. (TriSoil), Bacillus spp. (Valcure), garlic extract (NemGuard), etc. and this is continuously increasing through our research and development pipeline. With the soil biorational products we have developed a good knowledge not only on the products, but also in their interaction with biotic and abiotic soil components and with other similar products.
Our new company, Certis Belchim, in the future will continue to be particularly interested in this market segment and will be focusing mostly on biorational products. Our plans mainly encompass: (i) label extension to more crops and targets for the existing products; (ii) development and registration of new active ingredients for the control of soil borne pathogens, insects and nematodes; (iii) development of innovative formulations for soil use with focus on slow-release; (iv) field validation of effective programs with bio-solutions and other control methods.
In all these research and development activities, supported by the long experience we have in such topics, we are looking to generate our own IP solutions for soil pest management.
How have you seen this space evolve over the past of years, and what are you expecting the next years will bring?
From a technical perspective, we expect the nematode problems to increase globally in the future. This is due in part to the gradual global increase in average temperature, now recorded over recent decades, which will allow the most damaging nematodes, Meloidogyne spp., to establish at higher elevation and higher latitudes while in areas already infested, they will develop for a longer damaging period of time, thus leading to larger nematode soil population densities by the end of the crop cycle and, in turn, to greater damage to the succeeding crops.
From a regulatory perspective in Europe, if the approval process for new effective nematicides is not shortened and remains as restrictive as today, less effective solutions will be available, and there will be more reductions in rates and crops on which their use is permitted (e.g. not every year). This again will certainly lead to an increase in the severity of the nematodes that in many areas could be overlooked.
From a quarantine perspective, the globalization of trade has facilitated the introduction into Europe of new damaging nematodes and diseases and pests in general, events which are expected to increase in the future. The most critical situation can occur in protected and nursery crops, and for the production of healthy propagating material of annual crops, such as potato seed, bulbs and seeds of bulbous plant crops, including flowers, strawberry runners, woody nursery plants, of both crop and ornamental plants, and in all crops for which quarantine issues must be considered, especially when seeds, bulbs and any kind of plant propagating material are to be exported out of the EU.
The expectation is also that positive results will come from public research (more focus on resources is needed) and private industry where work is ongoing to bring to the market new biorational solutions and innovative methods with higher efficacy in controlling soil pests and to fulfill the increasing needs of this market. However, this will only be realized if regulatory hurdles are reduced in the EU, for example for low risk biorational solutions.
How are external factors (e.g., soaring input costs) impacting the adoption of these products?
Today agriculture and plant protection products, like the whole economy, are affected by higher prices due to the increased cost of energy and raw materials globally. Considering that the costs in agricultural production are already high and sometimes, those of soil pest control are not applicable for several crops, any further increase in production costs may lead to the abandonment of effective solutions, resulting in additional increase in the complexities of soil problems on our farms. This trend, if allowed to persist, will severely affect our agricultural sector.
This said, there will also be a potential increase in the new solutions entering the market in the coming years, which will face higher costs during development and the registration process as well.
From a technical perspective, the only way to reduce such risks is to support farmers with the right knowledge on how to use new soil products correctly (dose rate, timing and method of application, etc..) and increase cost effectiveness.
Can you share highlights of research and case studies that your company has conducted with respect to soil health?
Our company has been involved in many research and market studies dedicated to the soil pest management sector. The last important one was ‘Sustainability of European vegetable and strawberry production in relation to fumigation practices,’ prepared by a European team of independent soil experts. The aim of the study was to understand technically the role and economic impact of chemical soil fumigation in key European areas of vegetable and strawberry production. Three cases of representative crops were investigated: strawberries, solanaceous/cucurbitaceous crops cultivated under protected conditions and carrots as a relevant open field crop.
The study concluded that vegetable production is a key agricultural sector in Europe: including high-value crops like solanaceous and cucurbitaceous crops produced under protected conditions (tomatoes, peppers, aubergines, courgettes, cucumbers and melons), carrots and strawberries, the production value at farmer level is €12.5 billion; the cultivated area involved is roughly 330,000 ha. The importance of these crops is even greater when the entire food value chain, in economic and social terms, is also considered.
High standards in terms of food quality/safety and certificated production, along with affordable consumer prices and consistent availability across the seasons are demanded of European vegetable production and, as a consequence, are the drivers for the growers who have to protect such crops effectively and economically. The growers face very significant issues deriving from soil-borne pests, which are the key limiting factor to achieving quality and economically sustainable yields. As strongly indicated by farmers and crop experts, among the soil-borne pests, nematodes present the most impactful and frequent challenges.
According to the survey carried out in key EU countries (Spain, Italy, France, Belgium,…), the most common soil management practices for vegetable crops and strawberries are: chemical fumigation, crop rotation, resistant cultivars and rootstocks, followed by soil-less systems, non-fumigant treatments, soil solarization, biological products, organic soil amendments, catch and cover crops.
This shows clearly that soil pest management today and in the near future will rely on IPM systems combining and rotating different management practices, with a different degree of implementation depending on the cropping system.
Scientists at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) have recorded the first North American case of a harmful phytoplasma disease known for its threat to fruit, vegetable and ornamental crops in South America and the Middle East.
To make matters worse, scientists confirmed the host for the disease to be one of the most noxious and rapidly spreading weeds commonly found in a wide range of environments throughout the United States and into Canada.
Findings of the “First report of ‘Cadidatus Phytoplasma brasiliense‘ in North America and in a new host, yellow nutsedge (Cyperus esculentus)” were just published in the journal Plant Health Progress.
“The host of the disease is known as one of the most widespread and problematic weeds found everywhere—called yellow nutsedge,” said Brian Bahder, assistant professor of entomology at UF/IFAS Fort Lauderdale Research and Education Center. “It is one of the most aggressive weeds that commonly grows in lawns, home landscapes, vegetable and flower gardens and agricultural systems.”
The phytoplasma species called Candidatus Phytoplasma brasiliense is documented in regions of Brazil and Peru to harm hibiscus, papaya and cauliflower. Subsequently, research showed the same species infects peaches in the Middle East country of Azerbaijan.
Bahder and his team confirmed the phytoplasma and host in Fort Pierce. They found it while conducting research for a different disease—lethal bronzing—that attacks palm trees. Scientists were surveying and testing samples of grasses in hopes of finding a reservoir for lethal bronzing.
Research has shown that the adult planthopper insect that carries lethal bronzing feeds on the palm’s canopy, and the nymphs have been recorded among more than 40 species of grasses and sedges.
Because of the close association of nymphs with grasses and sedges, speculation has risen about the ability of these plants to serve as a reservoir for the lethal bronzing phytoplasma, Bahder said.
For the survey, scientists sampled three of the most abundant weeds known to serve as a host to the nymphs, yellow nutsedge being one of them.
While testing the samples, three of the outcomes resulted in a positive result.
“We thought we had found lethal bronzing in one of the grasses, so we proceeded to genetically sequence the sample,” said Bahder. “The results confirmed it was not lethal bronzing but that it was another phytoplasma.”
The DNA sequencing of that specimen confirmed their findings of a new phytoplasma in this weed, recorded for the first time in North America.
Implications of the disease and its spread through this weed cause scientists to consider it a threat to agriculture and ornamental industries. UF/IFAS scientists are seeking funding for the next steps of research.
“The next logical step is to find out which insect is spreading the disease. The good news is that we caught this early,” said Bahder. “We don’t know if this is an isolated incident or if the insect is spreading in the grass, and if it will feed on the papaya, hibiscus or cauliflower—which are economically important in Florida. The point is that we don’t know the extent of this disease in Florida or what threat it poses.”
More information: Brandon Di Lella et al, First report of ‘Candidatus Phytoplasma brasiliense’ in North America and in a new host, yellow nutsedge (Cyperus esculentus), Plant Health Progress (2022). DOI: 10.1094/PHP-03-22-0027-BR
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