First report of the occurrence of Asian citrus psyllid Diaphorina citri (Hemiptera: Liviidae), an invasive species in Nigeria, West Africa.

The Asian citrus psyllid (ACP; Diaphorina citri) is the vector of Candidatus Liberibacter asiaticus (CLas) that is associated with the devastating Huanglongbing (HLB; citrus greening disease). This pest of Asian origin has spread into the Americas and more recently into a few countries in East Africa. During recent surveys, suspect ACP adults and nymphs were recorded for the first time infesting citrus trees in southwest Nigeria. Morphological identification and DNA barcoding confirmed the samples to be D. citri. Analysis of the obtained sequences revealed that the ACP recorded in Nigeria clustered with other taxa in the previously identified B1 clade that consists of populations from different continents. The presence of the endosymbionts Ca. Carsonella ruddii and Ca. Profftella armatura in ACP from Nigeria was also confirmed by PCR and Sanger sequencing. The ACP individuals were assayed for the presence of CLaf, CLam and CLas by qPCR, but none of the insects tested positive for any of the Liberibacters. The prolific nature of ACP and the tropical climate prevailing in the citrus-producing areas of Nigeria and other West African countries may favor its rapid spread and population increase, thus posing a grave threat to the sustainability of citriculture in these countries.