Detection and monitoring of ‘Candidatus’ Liberibacter spp. vectors: African citrus triozid Trioza erytreae Del Guercio (Hemiptera: Triozidae) and Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) in citrus groves in East Africa

Abstract

The African citrus triozid (ACT) Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) and the Asian citrus psyllid (ACP) Diaphorina citri (Kuwayama) (Hemiptera: Liviidae) are primary vectors of the 'Candidatus' Liberibacter spp. ACT is associated with 'Candidatus Liberibacter africanus' (CLaf) causal agent of the African citrus greening disease (ACGD), whereas ACP vectors 'Candidatus Liberibacter asiaticus' (CLas) and 'Candidatus Liberibacter americanus' (CLam), the Asian and the American strains, respectively, associated with huanglongbing. 2 A preliminary survey in Kenyan citrus groves after the invasion of ACP had revealed that lime-green sticky traps (Asacp) were not effective in detecting and monitoring ACT and ACP. Therefore, this study compared eight differently coloured double-sided sticky traps to evaluate, which colour was most effective for detecting ACT and ACP, particularly at low densities. The traps were coded Red, Blue, Asgreen1, GLMgreen, Asacp, Asyellow, White, and Black. 3 Asyellow and GLMgreen traps captured more ACTs and ACPs than any other trap type. However, since there was no clear difference in the efficiency of Asyellow and GLMgreen in trapping ACP, any of the two trap types would be useful in the presence of both pests. 4 Among the eight traps, Asyellow and GLMgreen traps are potentially promising options for monitoring and detecting the pests in areas where they coexist. 5 Our findings will guide biosecurity agencies in decision-making and designing ecologically friendly integrated pest management (IPM) strategies for citrus greening vectors in Africa as well as serve as an early warning to safeguard against pests' invasion into unaffected areas.

Development of an Automated Multidirectional Pest Sampling Detection System Using Motorized Sticky Traps

“…In the future, the research team plans to fix this problem and further develop the algorithm's efficacy by better tuning and selecting the appropriate thresholds to make it capable of distinguishing other nonharmful insects from harmful ones. As far as the attractiveness of the proposed PSD is concerned the study results indicated that for the yellow sticky color, the mean number of captured insects per time was significantly higher [10][11][12]. The problem lays in the difficulty of identifying insects on traditional sticky traps based on their characters that are damaged because of weather conditions and some attacks by beneficial insects.…”

“…Yellow sticky paper traps consider an attractive color for the insects; these traps have been widely used in insect sampling practices as an effective tool associated with pest preference [10][11][12]. Sticky traps usually consist of a piece of paper containing a sticky substance to trap insects and are placed in fields or greenhouses [13,14].…”

“…Sampling is an important method of detecting insect infestation and estimating species abundance [12,15,16]. The use of traps for sampling insect pests is commonly practiced and is a vital part of pest detection, delimitation, suppression, and eradication programs worldwide.…”

The Asian Citrus Greening Disease (Huanglongbing): Evidence Note on Invasiveness and Potential Economic Impacts for East Africa

“…Although the liberibacters remained native to the particular zones where they were discovered, in modern times they have spread, along with their psyllid vectors, to new areas, along with their susceptible crops (aidoo). CLaf is transmitted by the African citrus triozid T. erytreae (del Guercio) (Triozidae), also known as the African citrus triozid (ACT) (Aidoo, 2020b). By contrast, CLas is transmitted by the Asian citrus psyllid (ACP) D. citri Kuwayama (Liviidae) (Graça & Korsten, 2004) (Figs.…”

“…A survey in Kenya compared eight differently coloured double-sided sticky traps to evaluate which colour was most effective for detecting ACT and ACP, particularly at low densities. Yellow and green traps captured more ACTs and ACPs than any other trap type(Aidoo et al, 2020b). Infected plants are more attractive to ACP due to HLB-induced volatiles.…”