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.
The influence of prior feeding experience and food deprivation on selection and utilization of wheat flour (WF), melon seed flour (MSF) and mung bean flour (MBF) by Tribolium castaneum reared on WF was investigated in this study. Flour selection, measured by percentage gravitation and acceptance of the flours by beetles (when fed and also when starved for 48 hours), was studied in choice and no-choice tests. On the other hand, T. castaneum’ s utilization of flours for growth and development was determined by monitoring population changes for three months in each flour type infested with 10 beetle pairs. Results of three-flour choice tests showed that gravitation (55.56%) and acceptance (54.44%) were significantly higher (p < 0.05) in WF than MSF and MBF. Also, MBF significantly (p < 0.05) had higher beetle gravitation (80.56%) and acceptance (72.78%) than MSF in a two-flour choice test. In no-choice tests, percentage gravitation and acceptance of beetles to the control (no flour situation) was significantly lower (p < 0.05) compared to MBF. Selection of MSF by T. castaneum was, however, not significantly different (p > 0.05) from the control in the study. Flour utilization followed a similar trend with significantly higher (p < 0.05) mean adults and larvae numbers in WF (211.33, 81.33) and MBF (87.67, 31.00), respectively compared to MSF (28.33, 7.67) at three months after infestation. The study concluded that flour selection in T. castaneum is influenced by prior feeding experience but not by food deprivation status of the beetles. Flour utilization is, however, neither influenced by prior feeding experience nor by food deprivation.
Key words: Tribolium castaneum, host range, choice test, no-choice test, flour
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