For the first years, IITA’s involvement in plant protection concerned only the development of resistant varieties. Then, since 1979, with the project on the biological control of cassava mealybug, IITA had to deal with a totally different approach where crop varieties still played a role but the main actors were introduced and indigenous predators and parasitoids. Against cassava mealybug the parasitoid Anagyrus lopezi out of Paraguay was first introduced to Nigeria in 1981 following quarantine in England by CABI. The parasitoid spread on its own, was again released in about 150 locations across the continent, and without failing brought the mealybug under control except in scattered locations with extremely bad soil conditions without mulching. Releases finished in 1994. The project brought the King Baudouin Award to IITA and the World Food Prize to Hans R. Herren, its former leader. Revenues for the farmers were calculated to be many billion US$.
With the same teams of national scientists across Africa and university staff world-wide, new projects were tackled. Cassava green mite, also out of South America, was brought under control in a vast belt across Africa by means of phytoseiid mites, particularly Typhlodromalus aripo with equally impressive returns in averted damage, directly to the farming communities.
Mango mealybug out of India was controlled by Gyranusoidea tebygi and Anagyrus mangicola until the introduction of an exotic fruit fly led some farmers to use insecticides excessively, leading to the destruction of the parasitoids and a resurgence of the mealybug. Good IPM practices are now being set in place, so that mango mealybug parasitoids can be active again. Spiraling whitefly for a short while became an important pest on several tree and field crops until its two parasitoids arrived serendipitously before IITA needed to introduce them. These parasitoids were subsequently also transferred out of Benin and established in Tanzania.
The introduction of the beetle Teretrius nigrescens against Prostephanus truncatus the larger grain borer which survives also on its host when attacking indigenous trees, seems to have had delayed impact, poorly documented, years after the project ended.
Beginning in the 1990s IITA was also involved in the biological control of three floating waterweeds that blocked waterways, affected trade, and brought an increase in waterborne diseases. Water hyacinth out of South America had already been combated in America, Asia, and Oceania. IITA with its proven collaborators released the weevil Neochetina eichhorniae across Africa. The worst infestations were stopped for good and high economic returns to the project were demonstrated, but control remained unsatisfactory particularly in eutrophic waters, asking for the introduction of still other biological control agents. Biological control was, however, a total success in the Lake Victoria Basin where Neochetina bruchi became dominant. Across West Africa, water lettuce was well controlled by the weevil Neohydronomus affinis. In the Congo, IITA was instrumental in controlling the aggressive water fern, which occurs only locally in West Africa, by means of the weevil Cyrtobagous salviniae.
Since 2000, many other projects were undertaken and are described by the corresponding authors.