Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stealth worms may improve insect pest control

07.03.2005


Nematodes comprise a worm family so large it literally covers the earth. They range in size from less than a micron in length to as much as 26 feet. Worldwide interest has begun to focus on microscopic nematodes that live with symbiotic bacteria.


Microscopic entomopathogenic nematodes measure just microns in length. (Photo: Patricia Stock)



"We study these nematodes - which are actually insect killers - not only to understand how diverse they are, but also to use them as biological control alternatives," says Patricia Stock, a nematomologist in the University of Arizona College of Agriculture and Life Sciences. "We want to see how they interact with the local insects. Using native biological control alternatives is more environmentally friendly than importing other pest control agents."

Known as entomopathogenic nematodes (EPN), the juvenile stage of these tiny worms travels with bacteria in its intestine that specifically kill certain insect species. Nematodes in the family Steinernematidae are associated with Xenorhabdus bacteria; those in the family Heterorhabditidae harbor Photorhabdus bacteria. Both types of EPN operate in similar ways. In the soil or in encrypted habitats such as the pockets behind the bark of trees, the juvenile nematode waits for (or sometimes actively seeks) an unsuspecting host - a grub or a larva - to jump on it and penetrate it through the insect’s natural openings - mouth, anus, spiracles. Or the nematode may enter the host directly by using a dorsal tooth.


Once inside the insect, the nematode vomits the pathogen, which kills the host within 24 to 48 hours and even digests its tissues, creating a perfect environment for the EPN to grow and multiply. One or more adult generations live entirely inside the decaying insect. The third stage infective juvenile is the only one that can live outside the insect host. Numbering about 150,000 strong or more, these juveniles exit the dead larva, carrying the bacteria, and look for other hosts to begin the cycle again. These juveniles also can survive dry conditions in soils for long periods of time before they infect more insects.

This naturally-occurring relationship between the nematodes and their mutualistic bacteria has existed for millennia. EPNs are found in terrestrial environments, including deserts, rainforests, grasslands and other ecological systems, offering a tremendous array of possibilities for study. Stock, who has been researching and interpreting the evolutionary relationships of nematodes for the past 15 years, has collected them in Arizona and from other locations worldwide.

In Costa Rica, for example, she is working with a collaborative team from four universities: the University of Vermont, University of Florida, University of Nebraska and University of Costa Rica, to learn where EPN communities are concentrated. The work is funded by the National Science Foundation. "We’re looking at all groups of nematodes in tropical rainforests," Stock says. "We sweep from the tops of the trees all the way to the ground, searching for nematodes that are potential insect pathogens. The misconception is that they are concentrated more in temperate zones, but this is not true. We’re trying to unveil the mystery of nematode diversity in the tropic regions."

In Jordan, she and her colleagues are surveying insect-parasitic nematodes from soil-inhabiting insects and other habitats. The International Arid Lands Consortium, which includes participating institutions from the United States and the Middle East, is sponsoring the project. The study will offer new information and tools for developing non-chemical and non-toxic pest control programs in desert and semi-desert areas. "These nematodes from Jordan have the potential to provide an environmentally safe alternative for controlling insect pests in agricultural and forestry systems, and also for controlling insect pests of human and veterinary importance," Stock says.

In each location the scientists start with biotic surveys to find out which nematodes and their corresponding bacteria meet local pest management goals. Then they gather samples from soil or other habitats for testing in the laboratory. The nematodes are accurately identified and analyzed using traditional morphology (structure and function) techniques and through molecular screening, including PCR (polymerase chain reaction) and DNA sequence analysis.

The researchers determine the nematode’s temperature and moisture requirements, the insect hosts it colonizes and other characteristics. Lists of EPN evolutionary associations, called phylogenies, are assembled to show how the nematodes have evolved in relation to each other and how they are related in a geographic region to affect similar hosts. "We always look at the insect and nematode interactions in the laboratory first, then go out and look at the crops and environment," Stock says. Some of her work involves comparing commercially available formulations of nematodes with custom- made applications of local nematodes.

In Arizona, Stock’s team is collecting native species of EPN for pest control trials in citrus and iceberg lettuce, with funding from the Arizona Citrus Research Council and the Arizona Iceberg Lettuce Research Council. Ninety percent of the citrus orchards in the state have the parasitic citrus nematode. "We’re looking for options in pest control," Stock says. "We’re using the entomopathogenic nematodes to antagonize the citrus nematode and other plant-parasitic nematodes and disrupt their life cycle and their infection into the citrus roots." This study is using commercially available nematode products along with isolates of nematodes collected from Arizona’s sky island (mountain) regions. For the lettuce trials, native nematodes gathered from the soil in Yuma will be used.

"It’s better to use native rather than exotic nematodes to preserve biodiversity," Stock says. It’s possible that similar species of nematodes can be used singly or together in reducing pest insect populations. Once the right nematodes are identified, they can be suspended in a gelatinous matrix, or dried in powder, then mixed in water and sprayed, broadcast or irrigated onto crops.

Large numbers of infectious juveniles are released to inundate and kill the pest insects quickly. Depending on climate conditions, this method works best on greenhouse ornamentals and vegetables, citrus, cranberry, turfgrass and other crops, rather than on high-acreage crops like cotton and soybeans. "The beauty of this is that in the last 20 years nematodes have been formulated and commercialized," Stock says. "They are more expensive than a chemical product, but so far they have been demonstrated not to harm humans, livestock, beneficial insects or the environment. Nematodes usually have to be underground; their targets are soil insects."

The formulations keep improving as newer isolates of nematodes are found, and there is a lot of commercial interest in matching nematodes to pests, Stock says. "Yet these nematodes are so powerful and pathogenic not in and of themselves, but because they live in symbiosis with bacteria," Stock concludes. "Both the bacteria and the nematode need each other to survive, making them not only good as biological agents, but also as model systems for understanding basic questions in biology." Given the number of nematodes that exist in the world, the possibilities for discovery are immense.

"The whole nematode phylum is estimated to have 500,000 to a million species. About 25,000 species have been identified so far," Stock says.

Patricia Stock | EurekAlert!
Further information:
http://www.arizona.edu

More articles from Life Sciences:

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

nachricht Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>