Citrus Greening, which is mainly caused by bacteria, is one of the severe citrus diseases affecting all citrus cultivars and causing the deliberate abolition of trees worldwide. This infectious disease cannot be spread by wind, rain, or contact by contaminated personnel. The primary vector that spreads this disease through feeding citrus leaves is the Asian citrus psyllid (ACP), a minuscule insect. The management of citrus greening is also very costly as there is no fruitful technique is developed to cure this disease except removing all infected plants from good ones to eliminate the dissemination of the pathogen. Citrus greening identification is also the most difficult job, as the symptoms are similar to other citrus diseases and nutrient deficiency. Asymmetrical blotchy mottling patterns on leaves are the main symptoms to detect this disease. Here we have discussed some visual signs of citrus greening, which will ultimately help root level farmers to identify and prevent this disease before it drastically impacts citrus plants. Whether it is affected by citrus greening or lack of nutrients, we have also discussed the pen test method of determining the symptoms as symmetrical or asymmetrical across the mid-vein.

Citrus greening disease or huanglongbing (HLB) caused by Candidatus Liberibacter asiaticus (CLas) limits the citrus production worldwide. CLas is transmitted by the Asian citrus psyllid (ACP), Diaphorina citri (Hemiptera: Psyllidae) in a persistent-propagative manner. Application of insecticides to manage the psyllid vectors and disease is the most common practice. Understanding the molecular interaction between CLas and ACP and interrupting the interrelationship can provide an alternative to insecticides for managing citrus greening disease. Transcriptome analysis of ACP in response to CLas showed differential expression of 3911 genes (2196 up-regulated, and 1715 down-regulated) including the key genes of ACP involved in cytoskeleton synthesis and nutrition-related proteins. Majority of the differentially expressed genes were categorized under molecular function followed by cellular components and biological processes. KEGG pathway analysis showed differential regulation of carbohydrate, nucleotide and energy metabolic pathways, the endocytotic pathway and the defense-related pathways. Differential regulation of genes associated with the key pathways might favors CLas to become systemic and propagate in its insect vector. The study provides an understanding of genes involved in circulation of CLas in ACP. The candidate genes involved in key physiological processes and CLas transmission by ACP would be potential targets for sustainable management of ACP and CLas.

Psyllids (Hemiptera: Psylloidea) can transmit the phloem restricted bacterium ‘Candidatus Liberibacter solanacearum’ (Lso). In Europe, Lso causes severe losses to carrot and represents a threat to the potato industry. A rising concern of Lso transmission from carrot to potato and within potato has driven the need for monitoring populations of psyllid species that could serve as vectors on both crops, which would provide a fundamental understanding of the epidemiology of this pathogen. Different sampling methods were used to survey populations of psyllid species in commercial carrot and potato fields in Central and Eastern mainland Spain from 2015 to 2017. Two psyllid species, Bactericera trigonica and Bactericera nigricornis were found to be mainly associated with carrot and potato crops. In carrot fields the most abundant species was B. trigonica occurring from crop emergence to harvest, whereas in potato crops the most abundant psyllid species was B. nigricornis. The maximum psyllid population occurred between June and October its timing depending on the field location. Since B. nigricornis was found on both carrot and potato and is the only psyllid species able to feed and breed on both these crops in Europe, there is the potential risk of Lso transmission from carrot to potato