No crisis yet: With confirmed resistance, western corn rootworm is worthy of being watched
Halting papaya pest saved over $300 mn for India
A natural pest-control plan from US-based Virginia Tech that halted the papaya mealybug – that created havoc in southern India causing mould and stunted growth of several crops – has saved up to $309 million in the first year itself.
For a relatively modest cost of $200,000 during the first year of the intervention, financial loss that would have crossed $1.34 billion over five years has been prevented, said researchers from Virginia Tech.
Led by an Indian-origin crop scientist Rangaswamy ‘Muni’ Muniappan, the Virginia Tech team first discovered this devastating papaya pest – called paracoccus marginatus – in India in 2008 and devised a natural way to combat it.
“India’s first efforts to eradicate the papaya mealybug failed,” said Muniappan, who heads Virginia Tech’s integrated pest management innovation lab programme. “The government and farmers tried spraying pesticides but crop losses kept getting larger. It was clear to us that this was a case not for poisons but for natural, biological controls.”
The winning intervention was based on three natural enemies of the mealybug – three parasitic wasps imported from Puerto Rico, Mexico, in July 2010. The wasp lays its eggs inside the mealybug larvae, and when the eggs hatch, the young wasps eat the larvae.
Excellent control of the papaya mealybug was obtained within five months, pesticide usage was reduced, and production and income were increased, said the research.
“I’m happy to hear that Virginia Tech scientists conducted an economic analysis. That is so often missing in biological-control projects,” said Marjorie A. Hoy, a University of Florida entomologist.
Publication date: 1/27/2014
This news release is available in German.
The biological term “symbiosis” refers to what economists and politicians usually call a win-win situation: a relationship between two partners which is beneficial to both. The mutualistic association between acacia plants and the ants that live on them is an excellent example: The plants provide food and accommodation in the form of food bodies and nectar as well as hollow thorns which can be used as nests. The ants return this favor by protecting the plants against herbivores. Researchers at the Max Planck Institute for Chemical Ecology in Jena, Germany, have now found that ants also keep harmful leaf pathogens in check. The presence of ants greatly reduces bacterial abundance on surfaces of leaves and has a visibly positive effect on plant health. Study results indicate that symbiotic bacteria colonizing the ants inhibit pathogen growth on the leaves. (New Phytologist, January 6, 2014, doi: 10.1111/nph.12664)
Myrmecophytes are plants which live in a symbiotic relationship with ants. The acacia species Acacia hindsii, which is native to tropical dry forests in Central America, is such a myrmecophyte. Its inhabitants are ants of the genus Pseudomyrmex. The ants depend completely on their host plants for nectar and the food bodies rich in proteins and lipids which they require. The acacia also provides shelter, the so-called domatia, in the hollows of its swollen thorns. In return for room and board, mutualistic Pseudomyrmex ferrugineus ants become bodyguards, protecting their host against herbivores and competing plants. However, some ants also benefit from the plant’s services without giving anything in return, such as the parasitic ant species Pseudomyrmex gracilis.
Scientists at the Max Planck Institute for Chemical Ecology have now looked more deeply into the insect-plant interaction, asking whether the tiny bodyguards also provide protection against microbial pathogens. They compared the leaves of acacia plants which were inhabited by either mutualistic or parasitic ants to leaves from which ants had been removed. Intriguingly, the leaves of acacia colonized by parasitic ants showed more leaf damage from herbivores and microbial pathogens than did the leaves that had mutualistic ants. The presence of the right symbiotic partner seemed to have a positive effect on the plant’s health.
Analysis of the surfaces of the leaves revealed that the number of plant pathogens as well as of necrotic plant tissues increased considerably when mutualisticPseudomyrmex ferrugineus ants were absent. These plants also showed strong immune responses in the form of an increased concentration of salicylic acid, a plant hormone which regulates defense against pathogens. Detailed analysis of the bacterial composition on the surfaces of the leaves suggested that the presence of mutualistic ants changed the bacterial populations and reduced harmful pathogens. Although far less pronounced, this effect could also be observed in parasitic ants.
How antimicrobial protection is transferred from ants to plant is still unclear. Chilean researcher Marcia González-Teuber, first author of the publication, suspected that microorganisms associated with the ants might play a role. Because acacia leaves are touched mainly by ants’ legs, she extracted the legs of mutualistic and parasitic ants and tested the effect of the extracts on the growth of bacterial pathogens in the lab. Plant pathogen Pseudomonas syringae was sensitive to the application of leg extracts of both ant species and its growth was inhibited. In the next step, the scientist isolated and identified bacteria from the legs of the ants. In lab tests, bacterial strains of the genera Bacillus, Lactococcus, Pantoeaand Burkholderia effectively inhibited the growth of Pseudomonas bacteria isolated from infected acacia leaves. Interestingly, some of the bacterial genera associated with the ants are known to produce antibiotic substances.
The Jena researchers have thus added another level of interaction to the symbiosis between ants and their host plants. “Such mutualistic relationships are much more complex than previously thought. In the future, we will have to include bacteria and other microorganisms in our considerations,” says Wilhelm Boland, head of the Department of Bioorganic Chemistry at the Max Planck Institute. Studies on symbiotic relationships between ants and myrmecophytic plants should not overlook the role of bacterial partners that help the ants protect “their” plants. [AO]
González-Teuber, M., Kaltenpoth, M., Boland, W. (2014). Mutualistic ants as an indirect defence against leaf pathogens. New Phytologist, DOI 10.1111/nph.12664
Prof. Dr. Wilhelm Boland, Max Planck Institute for Chemical Ecology, E-Mail firstname.lastname@example.org, Tel.: +49 3641 57 1201
Dec 05, 2013
(Phys.org) —University of Cambridge researchers have shown that viruses use aphids as pawns, discouraging the insects from permanently settling on already-infected crops and using this forced migration to spread infection to healthy vegetation.
Aphids are sap-sucking insects that attack many different types of plants and are major transmitters of crop-infecting viruses. By altering plant biochemistry, crop-infecting viruses cause vegetation to smell and taste unpleasant to visiting aphids. This repels the insects, causing them to move swiftly away to healthier plants, unwittingly transporting and spreading the virus.
This BBSRC-funded research could have significant impact on African agriculture. Working with various agencies, Dr John Carr and colleagues aim to help resource-poor farmers by deploying plants to act as aphid-decoys, drawing the insects away from crucial crops and halting the spread of infection through these farmers’ livelihoods.
About this research, Dr Carr said: “The work started almost accidentally when about five years ago a student and I noticed that aphids became sick or died when confined on a virus-infected plant. It’s an illustration of how research driven by curiosity can lead to findings that could have a positive impact in the real world – in this case in combating crop-damaging insects and the viruses they transmit.”
The Cambridge team collaborated with researchers at Imperial College, London, using Arabidopsis plants as hosts and monitoring the effect that the crop-infecting cucumber mosaic virus had. It was observed that the virus launched a concerted attack on the plant’s immune system whilst concurrently altering its biochemistry; in this way, the weakened Arabidopsis plant was unable to fight off either its attacker or visiting aphids. The aphids, instantly repelled by the smell and taste of the plant, left for healthier plants, but not before landing on the plant and contracting the virus. In this way, the mosaic virus ensured that the spread of the infection would be self-sustaining and highly efficient.
This research focuses on an example of what evolutionary biologist Richard Dawkins has called the ‘extended phenotype’. For Dawkins, the word ‘phenotype’ (the traits of an organism) should not be limited solely to biological processes, but should also be used to describe all effects that a gene has on the organism or environment in which it exists, or other organisms nearby. In this case, it was discovered that a virus influences the infected host, the Arabidopsis plant, and forces the host to change in a way that is beneficial to the parasite.
This revolutionary research has been done as part of a £16-million initiative to use bioscience in the improvement of food security in developing countries. Bioscience is playing an increasingly crucial part in meeting the challenges of feeding an ever-expanding population, projected to increase to 9 billion people by 2050. By developing ways to mitigate pest impact and reduce the spread of parasites, scientists are working to ensure successful harvests, now and in the future.
The study was published in the journal PLOS ONE.
Rice Pests of Bangladesh: Their Ecology and Management
by Zahirul Islam and David Catling
The University Press Limited, Dhaka, 2012; 422pages
This book takes a refreshing ecological approach to the management of rice pests in Bangladesh. Carefully laid out, easy to read and profusely illustrated, it is a single source for all rice pests, that is: insects, vertebrates, diseases, weeds, and draws on research efforts of the last 3-4 decades. It includes a new look at yield losses caused by insects and diseases, and analyzes ways and means of implementing IPM programmes.
The book is a ‘must’ for students, teachers, researchers, extension officers and agricultural development workers in Bangladesh and the eastern Indian states.
The book is available at:
The University Press Limited
Red Crescent House (5th Floor)
61Motijheel C/A, Dhaka1000, Bangladesh
Tel.: 9565441/9565444 Fax: 88029565543
E-mail: email@example.com; firstname.lastname@example.org
Price: Tk. 1600.00
NGAREMLEGUI STATE, PALAU. Dr. Aurora G. Del Rosario, Researcher/Extension Specialist, Palau Community College Research and Development Station.
For the past 20 years, research in Crop Protection proved to be a successful undertaking. Research culminated in the publication of two important books on crop protection.
The first publication written by Nelson Esguerra and Aurora Del Rosario is a 214-page book entitled “Economic Entomology in Micronesia” published by PCC-CRE and College of Micronesia in 2007. It showcases biological information on 84 major pests of crops in Micronesia which are described and augmented by 369 colored photographs of the damage and different life stages. Students in agricultural science as well as researchers and extension agents will find this book very useful.
The second book published by the COM Land Grant Program is entitled “Biological Control Introductions in the Freely Associated States of Micronesia”. It is a 136 –page document which covers the use of good insects to control pests of crops in the Freely Associated States of Micronesia from 1986 to 2009. Primarily, it involved introducing biological control agents in the Republic of Marshall Islands, the four island states of the Federated States of Micronesia and the Republic of Palau. Many of the introduced good insects reduced the target pests to non-damaging levels in these island nations. It also includes some biological control agents that remained in the islands and continuously controlled the pests despite releasing those 10-15 years ago. The authors are Nelson Esguerra, Aurora Del Rosario and Thomas Taro.