Incidence of Diaphorina citri Carrying Candidatus Liberibacter asiaticus in Brazil’s Citrus Belt

Abstract

Huanglongbing (HLB) is a citrus disease of worldwide importance, associated with the presence of Candidatus Liberibacter asiaticus (Las) and vectored by the psyllid Diaphorina citri in Asia and the Americas. To properly manage HLB, removal of inoculum sources and control of the psyllid are undertaken. We evaluated the percentage of the psyllid population with Las, sampled from yellow sticky traps over a three-year period and its relationship with insect population, regions, season of the year, and HLB management in citrus areas in the southwestern, central, and northern regions of São Paulo (SP) and southwestern region of Minas Gerais states, Brazil. In each reading, up to 50 psyllids per region were collected and detection of Las in individual psyllids were made by quantitative polymerase chain reaction. The percentage of psyllids with Las—an average of 65.3%—was constant throughout the year in the southwestern region of SP state, while showing an increase from spring to autumn when sampled from central to northern regions. The proportion of psyllids carrying Las from each region and year period were compared by a proportion test and spectral density analysis. The proportion of psyllids carrying Las evaluated in the same region in different seasons presented statistical differences in central (Araraquara) and southwestern (Santa Cruz do Rio Pardo) regions in 2015, with higher values in the first semester (summer and autumn) than in the second semester (winter and spring). Orchards with poor HLB management had higher incidence of psyllids with Las. Spectral density analysis indicated that good management areas had 50% less relevant peaks of psyllids with Las than in areas with poor HLB management practices. The relationship between the percentage of psyllids carrying Las and the number of captured psyllids in the region in a given time denotes the most critical intake time for HLB spread in citrus orchards. The reduction in the population of psyllids carrying Las is a direct benefit from the use of good management practices.

Climate‐induced range shifts of invasive species (Diaphorina citri Kuwayama)

“…In addition, most of the studies used only bioclimatic variables, whereas we used elevation in addition. Our model predictions were consistent with the current occurrence areas of ACP, including Nigeria, 20 Kenya and La Réunion, 24,36,39,72,73 Malaysia, 44 Mexico, 74 China, 40, 41 Uganda, Tanzania and Ethiopia, 42 and the USA 75 . Our study provides updated and detailed maps of the occurrence and potential global distribution of ACP under climate change.…”

Linking Climate Variables to Large-Scale Spatial Pattern and Risk of Citrus Huanglongbing: A Hierarchical Bayesian Modeling Approach

“…Consequently, a previous study by Alves et al (2020) indicated a greater spread of HLB in the regions bordering SP than those in central and south MG. Furthermore, CLas positive psyllids were in higher populations in southwestern and northern SP, compared to the state border between MG and SP (Wulff et al 2020). Combining the findings of Alves et al (2020) and Wulff et al (2020) one can speculate the support of results for this border effect in orchards of the current study.…”

Linking climate variables to large-scale spatial pattern and risk of citrus Huanglongbing: a hierarchical Bayesian modeling approach

“…Consequently, a previous study by Alves et al (2020) indicated a greater spread of HLB in the regions bordering SP than those in central and south MG. Furthermore, CLas positive psyllids were in higher populations in southwestern and northern SP, compared to the state border between MG and SP (Wulff et al 2020). Combining the findings of Alves et al (2020) and Wulff et al (2020) one can speculate the support of results for this border effect in orchards of the current study.…”