Biological control of cassava green mites in Africa: impact of the predatory mite Typhlodromalus aripo

摘要

Cassava was attacked in the 1970's by the cassava green mite Mononychellus tanajoa, a pest of neotropical origin. This pest is currently object of an Africa-wide classical biological control program using Typhlodromalus aripo, a predatory mite introduced from Brazil, South-America. Our study aimed at analysing the impact of T. aripo on M. tanajoa densities. Typhlodromalus aripo inhabits the apex of cassava plants during the day and forages on cassava leaves at night. Population dynamics study over seven consecutive years in cassava fields in Benin, West-Africa, showed a drop in cassava green mite densities since the introduction of T. aripo and an ability of the predator to tolerate environmental conditions prevailing in West-Africa and to persist periods of green mite scarcity by the use of alternative food, i.e. pollen of maize, an important intercrop in cassava growing areas. Densities of M. tanajoa and T. aripo are linked and generally follow the rainfall pattern, showing two peaks per year. Our study showed that T. aripo is suitable for controlling M. tanajoa. However, one should not underestimate the role of endemic predatory mites in addition to the impact of the exotic predatory mites on cassava green mites.