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 Antimicrobial substances identified in Komodo dragon blood
23.02.2017 | American Chemical Society

nachricht New Mechanisms of Gene Inactivation may prevent Aging and Cancer
23.02.2017 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>