The African citrus psyllid Trioza erytreae: An efficient vector of Candidatus Liberibacter asiaticus

Abstract

IntroductionHuanglonbing (HLB) is the most serious disease of citrus in the world, associated with three non-cultivable phloem-restricted bacteria Candidatus Liberibacter asiaticus (CLas), Ca L. africanus (CLaf) and Ca L. americanus (CLam). CLas is transmitted by the Asian citrus psyllid Diaphorina citri, and has spread to several countries. The African psyllid Trioza erytreae, the vector of CLaf occurs in Africa and neighbouring islands. Only two major citrus-growing regions - Australia/New Zealand and the Mediterranean Basin - are still HLB-free in the world. However, T. erytreae has recently been introduced into continental Europe (Portugal and Spain) and has become a potential threat to citrus production. The transmission of CLas by T. erytreae had been postulated but never tested. To evaluate the risk of T. erytreae transmitting CLas, comparative transmissions of CLas by T. erytreae and D. citri were assessed.MethodsTransmission tests were performed on excised leaves and seedlings of Citrus volkameriana with different inoculation access periods (in series) for both insect species. Quantifications of bacterial titers were made in excised leaves, seedlings three and six months after inoculation and on individual insects.ResultsOur results showed that T. erytreae was able to efficiently acquire CLas. Furthermore, T. erytreae carried significantly higher bacterial titers than D. citri, and was able to efficiently transmit the bacteria to seedlings at a similar rate that D. citri highlighting the high risk of spread of the most aggressive variant of HLB (CLas) by T. erytreae in Europe.DiscussionThus, extreme precautions to prevent any entry of CLas into Europe should be adopted.

Developing epidemiological preparedness for a plant disease invasion: modelling citrus huánglóngbìng in the European Union

“…AfCP has been found in many countries in Africa and the Middle East, and was detected in Europe in 2014 (Perez-Otero et al, 2015), with subsequent spread over large areas of northwestern Spain and western Portugal (EFSA et al, 2019b). It has been shown experimentally that both ACP and AfCP vector C Las (Reynaud et al, 2022), the most aggressive of the three bacteria causing HLB (Bové, 2006).…”

Seasonal Patterns in the Frequency of Candidatus Liberibacter Asiaticus in Populations of Diaphorina citri (Hemiptera: Psyllidae) in Florida

“…C Las is one of three putative causal agents for Huanglongbing [ 2 ]. Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the primary vector of C Las, but Trioza erytreae Del Guercio (Hemiptera: Triozidae) is also a vector [ 3 ]. Management activities are an additional production expense that reduces growers profits.…”

Risk-based regionalization approach for area-wide management of HLB vectors in the Mediterranean Basin

“…Conversely, both C Laf and AfCP are sensitive to hot and dry conditions, and are thus restricted to areas with relatively cool and humid environments ( Catling, 1969 ; Liu and Tsai, 2000 ; Bové, 2006 ; Dala-Paula et al., 2019 ). Both ACP and AfCP can transmit C Las and C Laf under experimental conditions ( Reynaud et al., 2022 ), but more research is needed to better understand the epidemiological implications of the C Las/AfCP and C Laf/ACP combinations.…”