Current Epidemic Situation and Control Status of Citrus Huanglongbing in Guangdong China: The Space–Time Pattern Analysis of Specific Orchards

Abstract

Huanglongbing (HLB) is the most harmful bacterial disease in citrus production in the world, and has been seriously ravaging the citrus groves of South China since the 1930s. The surveillance of the epidemiological characteristics of HLB is of utmost priority for citrus production in this region. In order to explore the effects of disease control measures, analyses on the space–time statistical features of the HLB epidemic, from 2019 to 2021, within six orchards in the Guangdong province are presented. Overall, the number of citrus plants in the orchards usually slightly decreased year by year. The reduction was mainly related to the level of plant susceptibility, which is correlated with citrus varieties. The maximum disease severity (incidence and race increment) was correlated with the awareness of this disease and the management intensity applied by the manager. A higher disease index was found in the conventional management orchards than in the comprehensive prevention and control orchards. Proper insect-protective screen houses can effectively prevent the epidemic of HLB, without affecting the fruit quality, and can also aid with higher yields. A high correlation was found between the geometry and topography of orchards and the HLB epidemic due to the wind direction from May to September and the Asia citrus psyllid activity characteristics. For flat orchards, the incidence of HLB in the north and entrance areas was higher than that in the southwest. In the mountain area, the incidence of the windward side in the south was higher than that of the leeward side in the north. Diseased trees tended to have an edge effect in the grove, whereas the trees of the same disease scale were found clustered in their distribution. These results allow a better understanding of HLB epidemiology and provide guidance for the early warning of HLB in new groves in areas that are severely affected by this disease. Furthermore, they also provide a scientific basis for the comprehensive prevention and control of HLB in old groves.

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

“…Based on proximity, CLas has been at Arcadia longer than locations at Fort Meade, Lake Wales, and Lake Alfred (all three locations are further north from the orig-inal detection locations (Figure 1)). Consequently, the low frequency of CLas at Arcadia would be consistent with the idea that an aggressive management strategy can reduce the proportion of infected psyllids and the rate at which the disease spreads [139][140][141][142][143][144]. An alternative narrative is that human movement resulted in a more rapid spread of CLas to more Northern sites.…”

Comparative Transcriptome and sRNAome Analysis Suggest Coordinated Citrus Immune Responses against Huanglongbing Disease

“…Despite optimistic scientific progress, HLB posed an unprecedented threat to the Chinese citrus industry. The Ministry of Agriculture and Rural Affairs of China listed it as one of the top ten crop diseases in 2020 [ 4 ].…”

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

“…Worldwide, citrus is an important crop, and HLB its most devastating disease (Gottwald, 2010). HLB has been reported in over 60 countries (Zhang et al, 2023), and impacts on the citrus industries of Brazil and the USA are significant. For example, since 2005 citrus production in Florida has decreased by 80%, whereas in Brazil over 64 million trees have been removed in São Paulo state (Graham et al, 2024).…”