Across the world, the tomato leafminer is wreaking havoc on agricultural producers. The relentless march of these pests inspired a team of Virginia Tech researchers to apply new methods of modeling and simulation previously used in infectious disease research to halt their spread. A new USAID grant will help them do just that.
The tomato leafminer, Tuta absoluta, is an innocuous-looking moth, easily hidden by the burgeoning foliage of young tomato plants. But once the eggs of the moth hatch, the larvae tunnel through the plants’ leaves, quickly giving a once green, productive field a scorched appearance. In Europe, West and Central Africa, and the Middle East, these pests have caused 50 percent to 100 percent crop loss since their accidental introduction to Europe in 2006.
“Entomologists normally use CLIMEX, a software modeling program that estimates the geographical distribution of an insect, and insect life tables, an analysis of an insect’s life cycle, to theorize how an insect will spread,” said Muni Muniappan, entomologist and director of the agricultural development program that is managing the grant. “But the Biocomplexity Institute is introducing human movement into the equation. This is a new angle.”
Managing these insects is not as simple as spraying insecticides. Virginia Tech’s Integrated Pest Management Innovation Lab works to provide solutions to farmers of developing nations using integrated pest management techniques that take into account the long-term health of people and ecosystems, as well as sustainable agricultural productivity.
However, halting the incredibly fast spread of these pests can be very difficult. Thus, researchers are turning to computational modeling in an effort to better understand when and where the insects will appear next. Using agent-based models in a novel approach, the research team will incorporate multiple data sources and find the most significant factors in the spread of these insects.
In the tomato leafminer study, the research team will view pest dynamics as an integrated biological, informational, social, and technical system consisting of several interacting models. This interaction-based approach is aimed at capturing the complexity of pest dynamics.
A key feature of this approach is understanding how humans hasten the speed at which pests spread. This includes not only human mobility but also supply chain infrastructures used to move goods across continents. These systems can have unintended side effects, one of which is the spread of invasive pests. This study will lead to a much better understanding of how human systems contribute to the spread of pest infestation.
“Our model will be an extremely useful tool for risk analysts, domain experts, and policy makers to develop strategies to combat these pests. Further, the methodology will not be limited to studying the tomato leafminer, but can be applied to any agricultural invasive species,” said Abjijin Adiga, research faculty member at the Biocomplexity Institute.
Alonna Wright works with a genetically selected mutant form of a nudivirus. The nudivirus causes a sexually transmitted disease only found in the corn earworm.
In nature, one-third of virus infection cases results in insect sterility. The genetically selected virus form causes an insect STD resulting in 100 percent sterility, which could give a boost to the naturally occurring virus to make it more effective.
“It’s a very labor intensive process, so when we finally got this mutant after months and months of screening, we were just so excited,” said Wright, an agricultural biotechnology student in University of Kentucky College of Agriculture, Food and Environment. “We knew this project was viable. We knew this could have an impact on millions of people and many crops. It was elating. I couldn’t be happier.”
The corn earworm causes an estimated $2 billion in damage and cost of control each year. Two closely related insects in South America and Asia are even more destructive.
A juvenile root-knot nematode, Meloidogyne incognita, penetrates a tomato root. Once inside, the juvenile, which also attacks cotton roots, causes a gall to form and robs the plant of nutrients. Photo by William Wergin and Richard Sayre. Colorized by Stephen Ausmus.
19th Biennial Group Meeting of the “All India Coordinated Research Project (AICRP) on Nematodes in Cropping Systems”
At the 19th Biennial Group Meeting of the “All India Coordinated Research Project (AICRP) on Nematodes in Cropping Systems” recently held at University of Agricultural and Horticultural Sciences, Shivamogga (Karnataka) India; experts from the country conveyed that an aggressive (with high reproduction rate, more damage to host plants and wide host range) root knot nematode, Meloidogyne enterolobii, got introduced and established through guava root stocks from Chhattisgarh, is causing huge losses in Dindigul, Coimbatore, Villupuram, Dharampuri and Krishnagiri districts of Tamil Nadu. The group emphasized that there is an urgent need to strengthen and enforce domestic quarantine mechanism to suspend spread of plant parasitic nematodes with vegetative propagules, especially through seed potatoes and rooted plants – along with soil, from nurseries/ sick plots/ hot-spot areas to disease free niches. In their opinion, presently nurseries in the country are having a field day and incorrigible for spreading pests without meeting any cleanliness standards or phytosanitary regulations. To break the pathway, it was suggested to enforce registration and licensing of plants and horticultural nurseries.
The recommendation from the Biennial Workshop is immensely important for reducing crop losses of horticultural crops in the country. Horticulture plant nurseries are extremely complex agricultural systems, recorded as pathways for several pests and diseases. Dr. Rajan said that the situation has become further cumbersome with ‘on line’ availability and sale of live ornamental and horticultural plants in the country. As disease management in nurseries/ green houses require specialisation; nematologists from the group ventured a draft road map – with details of detection, exclusion, risk analysis, critical control points for nursery stocks, infrastructure required for prophylactic measures, and costs involved for a prophylactic holistic system approach for registration/ certification for Nurseries and Green Houses.
In the address, Dr. D. J. Patel (Former Dean, Anand Agriculture University) and Dr. P. P. Reddy (Former Director, Indian Institute of Horticulture Research), well known experts in the subject expressed deep concerns about new nematode diseases in pomegranate, guava, coconut, banana, spices and vegetables all over the country through propagules. There is urgent need for policy support from Indian Council of Agricultural Research (ICAR), Department of Agriculture and Cooperation as well as Horticulture Mission for framing mandatory regulatory provisions for registration, licensing and certification of protected cultivation houses, nurseries and green houses especially for pest / quarantine requirements.
Dr. R. K. Walia, Project Coordinator (Nematodes), presented a brief history, background and the salient achievements of the AICRP on nematodes and overall scenario Plant Nematology research in India. He expressed serious concerns about the losses in crops due to nematode diseases and urged upon the nematologists to devise integrated approaches to manage root knot nematode (Meloidogyne spp.) problem in recently established poly-houses (for promoting cultivation of vegetables and ornamental) all over the country.
New publications “Pictorial guide on important nematode diseases of Karnataka”, “Comprehensive monograph of rice root-knot nematode (Meloidogyne graminicola)”, “Status of plant nematode diseases in Karnataka – a review”, and “Compendium of new plant parasitic nematode diseases of Karnataka”, along with a number of bulletins on serious issues were also launched on the occasion.
7 tips to keep pests – and pesticides – out of your garden
March 18, 2016
By Amer Fayad and Allen Straw
Amer Fayad is the associate director of the Integrated Pest Management Innovation Lab at Virginia Tech. Allen Straw is a specialist with Virginia Cooperative Extension focused on horticulture, small fruit and specialty crops.
Maybe you’re one of those backyard gardeners who can’t wait to get dirt under their fingernails. With the last-freeze date upon us, your motivation should be high!
Maybe this year you’ll consider doing something different – taking a step in the direction of a garden that is less toxic and more natural.
Virginia Tech experts can help you get there. The university’s agriculture scientists work overseas to prevent millions of dollars in crop damage – all by teaching practices known as integrated pest management. Closer to home, agents at Virginia Cooperative Extension work with commercial growers as well as backyard gardeners to spread some of the same seeds of knowledge.
Amer Fayad tries his hand at weighing yard long beans during site work in Nepal.
Based on our work in Asia, Africa and Latin America – as well as the commonwealth – we’ve come up with seven top tips.
Insects are your friends. So-called beneficial insects eat the pesky six-legged creatures that feast on your veggies and fruits. Familiarize yourself with the shape and color of the garden-friendly lady beetle, lacewing larva, praying mantis, ground beetle, robber fly, assassin bug and others so that you don’t kill them by mistake. (To that end, don’t indiscriminately spread poisons around, either.) Spiders are also excellent at keeping unwanted insects at bay.
You have a lot at stake when you plant a garden, so don’t forget the stakes. Trellises, cages and stakes are great ways to keep plants and leaves from trailing on the ground, where they become vulnerable to diseases and insects. Mulch is another practical aid to keep soil off your plants. Dirt isn’t a dirty word, but keep soil in its place!
Mimic nature’s timing – water your plants in the early morning. Dew clings to plants in the morning, so that’s when they’re accustomed to being wet. If you get the watering out of the way early, your plants won’t be drenched later in the day, when they’re sunning themselves. Practice drip-irrigation if you can.
Try a beneficial fungus called Trichoderma. In the United States, this unsung microbial agent is underutilized. But overseas, Virginia Tech scientists unleash this tiny hero as a parasite to scarf up other fungi before they can attack and destroy crops. Using Trichoderma as a soil amendment reduces harmful microorganisms and can give roots a boost, leading to more bountiful harvests.
Invest in floating row covers. In our international work, we often use netting. More common in the United States: employing fabric as an insect barrier. Floating row covers are often used to protect warm-weather plants from the first fall frosts. But they can also discourage marauding insects and even small rabbits or chipmunks. The lightweight fabric is placed directly over plants, protecting them from cucumber beetles and other pests for at least the first three or four weeks or until flowering. No need for a hoop or a tunnel. Simply anchor the fabric against the wind. Short hoops can be used when netting or other covering is employed to protect transplants such as tomatoes and peppers.
Practice interplanting. Instead of grouping plants together, vary the rows. This should slow the spread of insects or disease. You can also throw in some marigolds as well, which attract beneficial insects, though don’t expect miracles.
Don’t underestimate the power of your two hands. Wrap plant stems with aluminum foil near the soil line – this can shield tomatoes and peppers from cutworms. Pick off insects by hand. Set traps for slugs. If you see an infected leaf, remove it and dispose of it outside the garden. Clear out any vegetative refuse at the end of your gardening session.
At this point it may be time to stop reading and start weeding. If you’ve had your fill, get out and till. Just remember: On any continent, “prevention” is often a key word. It’s easier to deal with unwanted problems by heading them off rather than waiting until after they’ve wormed their way into your precious patch of earth.
[KAMPALA] A banana strain resistant to a common fungal disease could help smallholder farmers in East Africa better control the crippling disease, which has been spreading across the region over the last three decades.
The results of confined field trials of a genetically modified (GM) banana with improved resistance to a black sigatoga disease, the devastating leaf spot fungus, are promising, researchers have told SciDev.Net.
The disease is caused by the fungus Mycosphaerella fijiensis and it can halve fruit production in affected plantations. It is easily spread by airborne spores, rain, planting material, irrigation water and packing material used in transporting goods between banana-growing countries.
The dark leaf spots caused by the fungus eventually enlarge and merge together, causing much of the leaf area to dry.
The team led by Andrew Kiggundu — head of banana biotechnology research at the Uganda’s National Agricultural Research Laboratories Institute (NARL) in Kawanda — analysed 19 lines of GM bananas and found promising results in five of them. Andrews told SciDev.Net further research is needed to calculate the exact yield gains from using the resistant banana strain.
The researchers inserted genes for chitinase — an enzyme that breaks down chitin, the hard substance that makes up the cell walls of the invading fungi — preventing the fungus from invading the plant cells and causing the disease.
Kiggundu said laboratory tests using leaves from transgenic plants showed almost full immunity when cultured fungi were applied to the leaves.
Researchers collaborated closely with the Catholic University of Leuven in Belgium, where several banana lines were engineered to include the chitinase gene before being brought to NARL for testing.
However, Settumba Mukasa, resident banana expert in the department of crop science at Uganda’s Makerere University, said the field trials had more significance for building research capacity in Uganda than the development of a new disease-resistant banana.
“[The project] is a stepping stone for subsequent breeding programs and genetic engineering programmes. As a consequence of this project we can now do transformations of other varieties of bananas and other crop species,” said Mukasa.
While black sigatoka is among the top three diseases affecting bananas in Uganda it mainly affects Cavendish, which are not as widely cultivated as other types of bananas.
But for the few farmers in Uganda who do grow Cavendish bananas, the development may be useful since the disease is currently controlled by aerial pesticide spraying which is expensive for smallholders and affects their health.
“Farmers cannot afford that because they are small and they have few plants. Here, chemical control is not viable, so this approach may be the only available method to manage the disease,” Mukasa said.
Scientists in Japan have found a way to create high-yielding rice with long-lasting resistance to the devastating rice blast fungus.
Sufficient rice to feed 60 million people is destroyed by the blast fungus, Magnaporthe grisea — also known as Magnaporthe oryzae — every year.
Some rice is naturally resistant but is often also of lower yield. Now a team led by Shuichi Fukuoka from the National Institute of Agrobiological Sciences in Japan has engineered good quality rice that is both resistant to blast disease and high-yielding.
Their research was published in Science last week (21 August).
By comparing japonica rice that is resistant to blast disease with rice that succumbs to infection, Fukuoka found that a change in a key gene called Pi21 can mean the difference between devastating infection and mild disease.
Fukuoka says even plants with the resistant form of the gene become infected, but “The damage they suffer is not so serious, making it possible to reduce the amount of fungicide used by 50 per cent.”
He says his team’s findings will be particularly useful in mountainous areas where blast disease is a serious threat.
There have been many previous attempts to engineer resistant rice strains by making specific adjustments to plant immunity to allow the plants to recognise and resist the fungus.
But according to Nick Talbot, professor of molecular genetics at Exeter University in the UK, many of these modifications have a field life of just 2–3 years, as the fungus is quick to find ways to circumvent them and avoid being recognised.
Having the resistant form of Pi21, however, means a plant increases its defences against infection in general, making it much harder for the blast fungus to find a way to take hold, says Talbot.
He says the Japanese researchers have made a big discovery with universal applicability. When this is combined with other methods of engineering rice, scientists may be in a position to “exclude blast infections in a durable manner”.
Fukuoka has also managed to isolate the resistant form of Pi21, meaning it can be separated from other genes associated with poor yield. Previously this has been difficult because when scientists have tried to transfer the resistant Pi21 gene into new strains of rice, the genes affecting quality have also hitched a ride.
Fukuoka says the fact that his research has shown the exact location of the Pi21 gene means scientists can ensure it is not replaced by a more vulnerable form when breeding new rice strains.
The findings offer hope of limiting the impact of Xylella fastidiosa that experts described as one of the “most dangerous plant pathogens worldwide”.
If it is not controlled, it could decimate the EU olive oil industry.
The study, carried out by Italian researchers and funded by the European Food Safety Agency (EFSA), began in 2014 and consisted of two main types of experiment: artificial inoculation (via needle) and inoculation via infected vectors (insects) collected from the field.
The tests were carried out on a variety of species, including a range of olive, grape, stone-fruit (almond and cherry) and oak varieties.
“The first results are coming from the artificial inoculation because the field experiments began in the summer so it is only six months old, therefore only part of the results are available,” Giuseppe Stancanelli, head of the EFSA’s Plant and Animal Health Unit, told BBC News.
“The key results are that, 12-14 months after artificial inoculation on different olive varieties, the team found that young plants typically grown in the region displayed symptoms of the dieback.
“The research team also found evidence of the bacterium moving through the tree – towards it root system as well as towards the branches.”
But he added: “What has also been shown is that some varieties have shown some tolerance. They grow in infected orchards but do not show strong symptoms, as seen in more susceptible varieties.
“They are still infected by the inoculation but this infection is much slower so it takes longer for the infection to spread, and the concentration of the bacterium in the plant is much lower.
Dr Stancanelli added that these results were important in terms of providing information for tree breeders.
However, it was too early to say whether or not the olive yields from the varieties that have displayed tolerance to the infection are nonetheless reduced or adversely affected, he observed.
The EFSA Panel on Plant Health produced a report in January warning that the disease was known to affect other commercially important crops, including citrus, grapevines and stone-fruit.
However, the results from the latest experiments offered a glimmer of hope.
“Olives seemed to be the main host of this strain while citrus and grapes did not show infection, either in the field or by artificial inoculation,” Dr Stancanelli said.
He added that the infection did not spread through the citrus and grape plants that were artificially inoculated, and the bacterium was not found beyond the point it was introduced to the plant by injection.
But he added that more research was needed on stone-fruit species.
“The tests on the artificially inoculated varieties of stone-fruit need to be repeated because there is a mechanism in the plants that makes artificial inoculation difficult,” Dr Stancanelli explained.
“Another uncertainty we had was about (holm) oak. Quercus ilex is a typical Mediterranean oak that grows in the landscape and is natural vegetation.
“At the beginning of the outbreak in 2014, some symptoms were found on oaks and the tests were positive but this was never confirmed so this was probably a ‘false positive’.
“The artificial inoculation test appears to have shown that the holm oak is resistant (to the disease).”
The Xylella fastidiosa bacterium invades the vessels that a plant uses to transport water and nutrients, causing it to display symptoms such as scorching and wilting of its foliage, eventually followed by the death of the plant.
Since it was first detected in olive trees in Puglia, southern Italy, in October 2013, it has been recorded in a number of other locations, including southern France. To date, it has yet to be recorded in Spain, the world’s largest olive oil producer.
Experts warn that should the disease, which has numerous hosts and vectors, spread more widely then it has the potential to devastate the EU olive harvest.
Globally, the EU is the largest producer and consumer of olive oil. According to the European Commission, the 28-nation bloc produces 73% and consumes 66% of the the world’s olive oil.
Recent reports suggest that the X. fastidiosa outbreak has led to a 20% increase in olive oil prices during 2015.
In November 2015, the European Commission announced it was providing seven million euros (£5m) from the EU Horizon 2020 programme to fund research into the pathogen.
One of the areas of the Horizon 2020-funded research will be on plant selection to strengthen tolerance and resistance to the disease.
Dr Stancanelli explained that the experiments established in this study would continue as part of the EU-funded Ponte programme.
“The experimental field realized within the pilot project will serve as unique source of plant material for future project actions aiming at investigating the host-pathogen interactions,” he said.
“Investigations will be extended to an additional panel of 20 cultivars which will be planted in… April in the same plot.”
The disease plagued citrus farmers in North and South America for decades. It remained confined on these continents until the mid-1990s when it was recorded on pear trees in Taiwan.
According to the European and Mediterranean Plant Protection Organisation (EPPO), which co-ordinates plant protection efforts in the region, the pathogen had been detected prior to 2013 by member nations on imported coffee plants from South America. However, these plants were controlled and the bacterium did not make it into the wider environment.
Earlier this year, when a cold-tolerant subspecies of the bacterium was identified in the southern France outbreaks, UK government plant health officials published information for horticulture professionals, especially those importing plants. They were advised of their obligations – such as obtaining the necessary plant passports – and given details of the visible symptoms to look out for on potentially infected plants.