First record of the impact of the parasitism of Cecidochares connexa (Diptera: Tephritidae) by a solitary larval ectoparasitoid in West Africa: Cause for concern?

Cecidochares connexa is currently the only effective biological control agent of Chromolaena odorata an invasive weed in West Africa. Recently, an ectoparasitoid species belonging to the Ormyrus genus was found parasitizing C. connexa in three regions of Ghana. Adult parasitoid emergence percentages varied between 16 and 21%. This raises concerns about its impact on C. connexa populations and the overall biocontrol of C. odorata. New field surveys to determine the distribution range of Ormyrus sp. and its impact on C. connexa should be quickly addressed in West Africa

First record of the impact of the parasitism of Cecidochares connexa (Diptera: Tephritidae) by a solitary larval ectoparasitoid in West Africa: Cause for concern?

Cecidochares connexa is currently the only effective biological control agent of Chromolaena odorata an invasive weed in West Africa. Recently, an ectoparasitoid species belonging to the Ormyrus genus was found parasitizing C. connexa in three regions of Ghana. Adult parasitoid emergence percentages varied between 16 and 21%. This raises concerns about its impact on C. connexa populations and the overall biocontrol of C. odorata. New field surveys to determine the distribution range of Ormyrus sp. and its impact on C. connexa should be quickly addressed in West Africa

With or without you: stem-galling of a tephritid fly reduces the vegetative and reproductive performance of the invasive plant Chromolaena odorata (Asteraceae) both alone and in combination with another agent

With or without another biological control agent, the specialist folivore Pareuchaetes pseudoinsulata, the stem-galling fly Cecidochares connexa reduced the performance of the invasive alien plant, Chromolaena odorata in Ghana. There was a strong significant negative relationship between gall densities of the gall fly and stem height, and the number of stems and flower heads of C. odorata. Pareuchaetes pseudoinsulata had very little impact on any C. odorata parameters. However, at sites where both C. connexa and P. pseudoinsulata occurred simultaneously, the performance of C. odorata was significantly reduced when compared with control plants. Increasing densities of both agents had a strong significant negative correlative effect on C. odorata plant parameters. Cecidochares connexa was recorded in all five regions of the country sampled, while P. pseudoinsulata was recorded in four regions. Densities of both agents declined in the dry season, but galls were persistent throughout the study period. This is the first report of the impact of C. connexa on C. odorata in the West African sub-region since its introduction to Cote d’Ivoire in 2003 and it is clear that the agent has a significant impact on C. odorata in Ghana. Further surveys are required to determine the impact of both biological control agents in other parts of the sub-region where they have established

With or without you: stem-galling of a tephritid fly reduces the vegetative and reproductive performance of the invasive plant Chromolaena odorata (Asteraceae) both alone and in combination with another agent

With or without another biological control agent, the specialist folivore Pareuchaetes pseudoinsulata, the stem-galling fly Cecidochares connexa reduced the performance of the invasive alien plant, Chromolaena odorata in Ghana. There was a strong significant negative relationship between gall densities of the gall fly and stem height, and the number of stems and flower heads of C. odorata. Pareuchaetes pseudoinsulata had very little impact on any C. odorata parameters. However, at sites where both C. connexa and P. pseudoinsulata occurred simultaneously, the performance of C. odorata was significantly reduced when compared with control plants. Increasing densities of both agents had a strong significant negative correlative effect on C. odorata plant parameters. Cecidochares connexa was recorded in all five regions of the country sampled, while P. pseudoinsulata was recorded in four regions. Densities of both agents declined in the dry season, but galls were persistent throughout the study period. This is the first report of the impact of C. connexa on C. odorata in the West African sub-region since its introduction to Cote d’Ivoire in 2003 and it is clear that the agent has a significant impact on C. odorata in Ghana. Further surveys are required to determine the impact of both biological control agents in other parts of the sub-region where they have established

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).

The Neotropical invasive plant Chromolaena odorata R.M. King and H. Robinson (Asteraceae) 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 biodiversity, have established. The stem-galling fly, Cecidochares connexa (Macquart) (Diptera: Tephritidae), has spread widely across West Africa since its release in only Côte d'Ivoire, occurring in six countries. This study aimed to investigate whether the gall fly had spread further across West Africa and into Central Africa. Here, we surveyed C. odorata for C. connexa 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 surveyed 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 Côte d'Ivoire into Cameroon, covering over 2,300 km. Following the spread and establishment of C. connexa 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

Eight decades of invasion by Chromolaena odorata (Asteraceae) and its biological control in West Africa: the story so far

Chromolaena odorata (L.) R.M. King and H. Robinson (Asteraceae) is a perennial weedy shrub of neotropical origin and a serious biotic threat in its invasive range. The Asian-West Africa (AWA) biotype of C. odorata present in West Africa is both morphologically and genetically different from the southern African (SA) biotype. The AWA biotype was first introduced into Nigeria in the late 1930s and rapidly spread across West Africa. Currently, 12 of the 16 countries in West Africa have been invaded, with significant negative effects on indigenous flora and fauna. However, locals in West Africa have found several uses for the weed. As chemical, physical and other conventional methods were unsustainable, costly and largely ineffective, three biological control agents, Apion brunneonigrum (Coleoptera: Brentidae), Pareuchaetes pseudoinsulata (Lepidoptera: Erebidae) and Cecidochares connexa (Diptera: Tephritidae), have been released in West Africa between the 1970s and the early 2000s. However, only C. connexa and P. pseudoinsulata established, contributing to the control of the weed, in six and four countries in West Africa respectively. Limited research funding, the absence of post-release evaluations of the established agents, and the ?conflict of interest? status of C. odorata (i.e. being beneficial for local use but damaging to ecosystem services and agriculture), are serious factors deterring the overall biological control effort. Here, using historical records and field surveys, we examine the invasion history, spread, impacts, and management of C. odorata in West Africa and make recommendations for the sustainable management of C. odorata in the region