Abstract
BackgroundThe insect vector of Huanglongbing, Diaphorina citri Kuwayama, 1908 (Hemiptera: Lividae) was detected in Ecuador in 2013 and its main parasitoid Tamarixia radiata (Waterston, 1922) (Hymenoptera: Eulophidae) was reported for the first time in 2017. In the citrus production region of Manabí province, Ecuador, D. citri and T. radiata were reported for the first time on Murraya paniculata L. in 2016 and 2018, respectively. D. citri was first found infesting Citrus x aurantiifolia (Christm.) Swingle in Manabí province at the end of 2018. The present study was conducted between August 2018 and May 2021 to: (1) monitor D. citri populations on M. paniculata and C. x aurantiifolia and determine the parasitism rates of T. radiata on D. citri nymphs on both host plants, (2) establish the occurrence of T. radiata parasitizing D. citri on C. x aurantiifolia, and (3) calculate a predictive model for estimating the number of parasitized nymphs on a planting lot of M. paniculata and a C. aurantiifolia orchard.ResultsDiaphorina citri populations on M. paniculata decreased from 11 nymphs (2018–2019) to approximately 2 nymphs per flush (2020). This was associated with a natural increase in parasitism rates of T. radiata from 20% (2018) to 96% in 2020. The regression equation (Y = 2.049Ln (x) + 5.88) was able to estimate the number of parasitized D. citri nymphs based on parasitism on M. paniculata (R2: 0.8315). Tamarixia radiata was first detected on C. x aurantiifolia in July 2020. Populations of D. citri reached 55 nymphs per flush (no parasitism) and subsequently decreased to the minimum level of 14 nymphs per flush (parasitism rates of up to 31%). The model allowed estimating the number of parasitized nymphs by T. radiata on M. paniculata and C. x aurantiifolia, with a maximum deviation of approximately 2 nymphs.ConclusionsBased on the colonization and establishment of the psyllid–parasitoid interaction on M. paniculata, it is estimated that approximately by the end of 2022, populations of D. citri on C. x aurantiifolia would decline due to the highest percentages of parasitism by T. radiata. High parasitism rates may indicate the potential of T. radiata in conservation biological control and integrated pest management programs.
Highlights
The insect vector of Huanglongbing, Diaphorina citri Kuwayama, 1908 (Hemiptera: Lividae) was detected in Ecuador in 2013 and its main parasitoid Tamarixia radiata (Waterston, 1922) (Hymenoptera: Eulophidae) was reported for the first time in 2017
As rainfall decreases, the rutaceous plants start to produce young shoots, which are ideal for the development of D. citri nymphs, resulting in a population increase
The importance of T. radiata as a biocontrol agent of D. citri on M. paniculata was supported by the high inverse correlation (r: − 0.9119, P < 0.05) between the number of parasitized and non-parasitized D. citri nymphs that resulted in high parasitism rates (Fig. 3a)
Summary
The insect vector of Huanglongbing, Diaphorina citri Kuwayama, 1908 (Hemiptera: Lividae) was detected in Ecuador in 2013 and its main parasitoid Tamarixia radiata (Waterston, 1922) (Hymenoptera: Eulophidae) was reported for the first time in 2017. One of the potential threats to the Ecuadorian citrus industry is Huanglongbing, considered the most destructive disease of citrus worldwide, caused by the bacteria Candidatus Liberibacter spp. that obstruct the phloem and can cause the eventual death of the plant (Bové 2006) This disease has not yet been reported in Ecuador, in 2013, its known insect vector in the Americas, the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera, Liviidae) was detected in the coastal province of Guayas on both, Citrus spp. (Rutaceae) as well as on the ornamental plant host, orange jasmine, Murraya paniculata (L.) Jack (Rutaceae) (Cornejo and Chica 2014) It spread to different citrus regions on Ecuador (Cuadros et al 2020). T. radiata was reported in other provinces of Ecuador, in the coast (Cuadros et al 2020) and the highlands (Erraez et al 2020)
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