Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cassava mealybug control : parasitoid wasps hold the kairomone key

13.02.2002


The mealybug Phenacoccus herreni feeds on cassava plant sap, inducing shrivelling. It causes extensive damage in cassava growing areas in South America. However, it can be parasitized by two wasps, Acerophagus coccois and Aenasius vexans which act out a ritual to recognize and select the individuals they are going to parasitize. A wasp moves from one side to the other of a potential victim, investigating it by palpation with their antennae. Once this “drumming and turning” procedure completed, the wasps carry out their oviposition. And when the parasites emerge, the mealybugs die.



The IRD researchers, working jointly with the International Center for Tropical Agriculture (CIAT) in Colombia, have been focusing on chemical signals which enable the wasps to recognize their victims. They showed that a kairomone, an ester called O-caffeoylserine, acts as a cue in this recognition mechanism. It is secreted by the mealybug and is present on its body surface and can be recognized when the wasp comes into contact with it. The ester makes up 0.03 nmol/mg of the mealybug body weight.

O-caffeoylserine was isolated from a sample of mashed adult female mealybugs, the development stage at which the wasps prefer to lay their eggs. This is a new result for science. Although known in an artificially-synthesized form, this ester had never been obtained before from natural biological source material.


The researchers subsequently demonstrated that the O-caffeoylserine was indeed recognized by the wasps. This they did by studying their behaviour in response to small balls of cotton made to look like mealybug bodies, some soaked in an ordinary solvent, others imbibed with O-caffeoylserine. Neither Acerophagus coccois nor Aenasius vexans “recognized” the former, but they investigated those impregnated with the substance and sometimes tried to insert their ovipositor, the egg-laying organ.

These “decoys” also enabled the researchers to determine the concentration at which the ester is most attractive. Cotton balls were soaked with different concentrations of the product then presented to the wasps. The recognition ritual was observed only with concentrations of between 0.015 and 0.03 nmol/mg. Oviposition rarely took place and only when concentration was 0.03 nmol/mg.

What benefit then does O-caffeoylserine offer the mealybug? It appears to have a dual action. It could take part in cuticle sclerotization and tanning. Or it could have a protective role against bacteria and viruses. In any case, it would have a role which is essential.

Yet, perversely, the compound is paramount in attracting the parasitoid wasps to their mealybug victims. Many scientific studies have shown that a parasite is more effective if it has already been in contact with its host or a substance which this synthesizes. Thus, if parasitoid wasps were put artificially into contact with this kairomone, in insect collections for example, they would then be able to parasitize the mealybug more rapidly. The discovery of this substance is therefore an important step towards developing a more effective biological control method against this serious pest.

(1) a chemical compound beneficial for the insect which receives the “message” (in this case the parasitoid wasp) and harmful for the one which emits it (the mealybug).

Marie-Lise Sabrie | alphagalileo
Further information:
http://www.ird.fr

More articles from Life Sciences:

nachricht Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz

nachricht Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB

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

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | 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

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>