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.
Marie-Lise Sabrie | alphagalileo
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