Classical biological control of the African citrus psyllid Trioza erytreae, a major threat to the European citrus industry

Abstract

Citrus greening or huanglongbing (HLB) is the main threat to the European citrus industry since one of its vectors, the African citrus psyllid, Trioza erytreae , has recently become established in mainland Europe. In this context, classical biological control programmes should be implemented to reduce the spread of the psyllid. The aims of this study were to: i) disentangle the parasitoid complex of T . erytreae combining morphological and molecular characterization; and ii) to study the biology of its main parasitoids in its area of origin in South Africa for their future importation into Europe. The main citrus producing areas of South Africa were surveyed during 2017. In contrast to previous studies, the parasitoid complex of T . erytreae included three species of primary parasitoids: Tamarixia dryi , Psyllaephagus pulvinatus and another parasitoid of the genus Tamarixia . Molecular analysis showed that it is a new species closely related to T . dryi . Tamarixia dryi was the most abundant parasitoid but its relative abundance varied among sampling sites. The sex ratio (males/females) of T . dryi and Tamarixia sp. decreased with T . erytreae size and became female biased when psyllid nymphs were larger than 0.6 and 1.2 mm 2 , respectively. These parasitoids were attacked by three species of hyperparasitoids, Aphidencyrtus cassatus , Marietta javensis and a species of the genus Aphanogmus . Aphidencyrtus cassatus , the most abundant hyperparasitoid, tended to emerge from large nymphs, and adult females lived as long as those of T . dryi . The implications of these results are discussed within the framework of the introduction of T . dryi into Europe.

Mitochondrial genetic variation reveals phylogeographic structure and cryptic diversity in Trioza erytreae

“…www.nature.com/scientificreports www.nature.com/scientificreports/ Intraspecific diversity of Trioza erytreae. The intraspecific genetic diversity of T. erytreae was assessed using a dataset of COI barcoding sequences identified as T. erytreae collected in Africa and Europe in two previous studies 25,26 (Table S4). The final COI dataset (n = 89) included the three sequences generated in the present study, and was strongly biased towards Kenya, which represented 75.2% of all sequences (n = 66), followed by South Africa (14.6%; n = 13).…”

“…As the control of T. erytreae is directly linked to the management of ACG, understanding the bioecology of the triozid is relevant for its management and control 23,24 . The genetic diversity and phylogeographic structure of T. erytreae are largely unknown, except for a study which focused on the generation of DNA barcodes for species identification in the genus Trioza 25 , and a recent work aimed at testing the host range of Tamarixia dryi, a parasitoid wasp associated with T. erytreae in South Africa 26 .…”

Metabolomics as an Emerging Tool for the Study of Plant–Pathogen Interactions

“…Liberibacter africanus [108], which can be introduced into the plant by two psyllid vectors: Diaphorina citri and Trioza erytreae [109]. T. erytreae is endemic to Africa, but was recently detected in some European countries [110], posing a serious threat to citrus production in these regions. Huanglongbing is a complicated pathosystem to study and has also proven difficult to manage in the field; no treatments or resistance are known for the disease [111].…”

Water Vapor Pressure Deficit in Portugal and Implications for the Development of the Invasive African Citrus Psyllid Trioza erytreae

“…The minimum base temperature for T. erytreae is 10-12 • C [19]. Therefore, control measures, such as classical biological control with the introduction of Tamarixia dryi, an efficient and specialist parasitoid [24][25][26], and chemical control (mainly with neonicotinoid insecticides), may be focused on spring flush when the weather is favorable to insect survival and development. With warmer summers, smaller populations of T. erytreae are expected; however the insect should be sampled regularly for the presence of CLaf and controlled in an area-wide manner [27].…”