Marching across and beyond West Africa: First record of the stem-galling fly Cecidochares connexa (Diptera: Tephritidae) in Central Africa and the implications for biological control of Chromolaena odorata (Asteraceae)
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Date
2021
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Publisher
PLOS
Abstract
The Neotropical invasive plant Chromolaena odorata R.M. King and H. Robinson (Astera ceae) is a serious weed in West and Central Africa and two biological control agents that
have been introduced into West Africa to help reduce its impacts on agriculture and biodiver sity, have established. The stem-galling fly, Cecidochares connexa (Macquart) (Diptera:
Tephritidae), has spread widely across West Africa since its release in only Coˆte d’Ivoire,
occurring in six countries. This study aimed to investigate whether the gall fly had spread fur ther across West Africa and into Central Africa. Here, we surveyed C. odorata for C. con nexa galls in Cameroon between October 2018 and October 2020, along roadsides, on
farms, residential areas, and abandoned plots, encompassing various vegetation types.
Additional surveys were conducted across four countries (Ghana, Togo, Benin Republic
and Nigeria) in West Africa that we considered the probable pathway for the spread of the
gall fly into Central Africa. Cecidochares connexa was present at five of the six locations sur veyed in Cameroon, albeit in varying abundance. In Africa, these findings represent the first ever report of C. connexa outside of West Africa. In West Africa, we recorded significant
expansion in the geographic range of C. connexa, as reflected in the absent-present record
of C. connexa in two locations in Nigeria and one in Ghana, as well as its occurrence in all
locations surveyed in Benin Republic and Togo. Clearly, Ghana, Togo, Benin Republic and
Nigeria served as the dispersal pathway of C. connexa from the release sites in Coˆte d’Ivoire
into Cameroon, covering over 2,300 km. Following the spread and establishment of C. con nexa into Cameroon, we anticipate that it will continue to spread further into other parts of
Central Africa which are climatically suitable. Cecidochares connexa is currently the only
biological control agent for C. odorata in Central Africa. Given that it has significantly
reduced populations of C. odorata in other countries where it has established, it is expected
to have a similar impact in Central Africa.
Description
Research Article