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The Phenacoccus herreni mealybug, which causes extensive damage to cassava crops in South America, can be kept at bay by two types of wasp that lay their eggs in the pest.

Now, researchers hope to make these wasps more effective at killing mealybugs by strengthening the way in which they identify their victims.

A group of researchers from the French Institute of Research for Development (IRD), and the International Center for Tropical Agriculture (CIAT) in Colombia have found that the wasps are attracted to a substance called O-caffeoylserine, released by the mealybug. The wasps then lay their eggs inside the mealybugs, which are killed when the parasites emerge.

The researchers say that if the two types of wasp — known as Acerophagus coccois and Aenasius vexans — were artificially put into contact with this substance, they might be able to recognise the mealybug more effectively, leading to better control of the pest.

Many previous scientific studies have shown that parasites are more effective if they have already been in contact with their host or a substance synthesised by the host.

But Peter Neuenschwander, director of the International Institute of Tropical Agriculture’s African Centre for Biological Control in Benin, doubts whether the finding could lead to improved biological control methods.

“Maybe we shouldn’t jump too quickly to an application, because in the past such findings (for other types of mealybug) have not led to a practical application,” he says.

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