When the country implemented a national lockdown and travel restrictions due to the current health crisis, Paul-André Calatayud and his kenyan colleagues had to find a way to ensure that their research and laboratory work could keep going. They indeed cannot stop their activity as they breed insects that require daily care.

Paul-André is an IRD researcher, based at the International Centre of Insect Physiology and Ecology (icipe), in Nairobi, since 2016. When not working from home, the researchers followed the new requirements within the research organization: wearing a mask, temperature control, hand and instrument disinfection, etc.

Paul-André Calatayud.

© icipe

Thanks to all this, they were able to continue their research on biological control of crop pests. Pest maize caterpillars cause significant damage to farmers. French and Kenyan authorities have always used pesticides to control them, not without a major impact on human and environmental health. “We look for solutions to control pest populations in a biological way, without pesticides. One of the solutions is to use insect enemies to these crop pests, such as small wasps parasitizing the pests, called parasitoids", Paul-André explained.

The scientists breed the pests and their parasitoids at icipe, following two main steps, every week.

Cages where pests lay their eggs.

© IRD - Paul-André Calatayud

  • Breeding of parasitoid host insects: the maize stemborers

As scientists study parasitoids, nothing is better than providing them with their host insects, raised in the laboratory. They first mate the male and female moths (the maize stemborers), then place them in cages where females lay their eggs on surrogate paper stem of maize. The eggs are collected and set aside until they hatch. The resulting caterpillars are reared in an artificial environment reproducing the components found in maize, prepared by the IRD team based at icipe. This semi-solid artificial diet is made of, among other things, sugar, vitamins and proteins in agar-agar.

Parasitoids hatch and form cocoons around the pest caterpillar.

© IRD - Paul-André Calatayud

  • Breeding of parasitoids

The IRD team and its partners have identified one of the two new insects used to control maize pests. These parasitoid wasps are also bred by the scientists at icipe. They present a caterpillar to a parasitoid female, who lays her eggs there. Once the caterpillar is parasitized, it is transferred to the artificial environment, where it continues to slowly feed. After ten days, the parasitoid wasps leave the body of the caterpillar and form a mass of small cocoons around it. The caterpillar dies. These masses of cocoons are collected and incubated until the emergence of adult wasps, which will take part in series of tests to assess their impact on the population of maize pests.


Pests biological control in video: