The distribution and abundance of the stem-galling fly, Cecidochares connexa (Macquart)(Diptera: Tephritidae), a biological control agent of Chromolaena odorata (L.)(Asteraceae), in Ghana

Abstract

Chromolaena or Siam weed is one of the worst invasive weeds in West Africa and a serious threat to food security. The stem-galling fly was released in the Ivory Coast in 2003 and first detected in Ghana in 2014. Its distribution and abundance in Ghana was determined by country-wide surveys in 2015 and 2016. Galls were found at varying densities across Ghana and also in Togo in low numbers. The gall fly has dispersed about 1000 km in ten years and, while there is some evidence that the gall fly is still moving eastwards, its range and densities could be limited by the dry climatic conditions. Actively redistributing the agent over this dry corridor to the more humid and higher rainfall areas of Nigeria, may result in its spread through the rest of West and Central Africa, thereby aiding the control of chromolaena in the region.