Phloem Limited Citrus Pathogens in the 21st Century: Distribution, Diagnostics and Management Strategies
DOI:
https://doi.org/10.66835/psh.2026.e0006
Keywords:
Citrus, Phloem-associated diseases, Huanglongbing (HLB), Phytoplasma, Disease managementAbstract
Citrus is regarded as a fruit crop that is economically significant worldwide, serving as a source of nutrition, a driver of job creation, and a key contributor to global agricultural trade. However, the agricultural productivity of citrus is being limited by a set of devastating diseases that are caused by the phloem-affirming or phloem-confined pathogens commonly known as the plasma diseases. Diverse biological agents such as phloem-limited bacteria, including Candidatus Liberibacter spp. Spiroplasma citri is responsible for Huanglongbing, citrus stubborn disease. Phytoplasmas cause symptoms of decline and witches’ broom, while a variety of citrus viroids, such as citrus Exocortis viroid or Hop stunt viroid, cause these diseases. These pathogens inhabit the phloem tissues, interfere with the movement of photo assimilates, and compromise root systems, eventually leading to a decline in yields, decline in fruit quality, and mortality of the trees. These phloem-restricted citrus diseases are known to be systemic, highly latent, and variably symptomatic and are ascribed to being effectively transmitted by insect vectors or non-sterile propagation media. Over the last few decades, changes in the incidence and the spread geographically of these diseases have risen steeply owing to increased global trade of plants, proliferation of vectors, and alterations in the ecology of vectors caused by climate change. The systems of weak certification, informal nurseries, scanty diagnostic infrastructure, as well as unsatisfactory management of vectors have also made citrus orchards in Asia, including Pakistan, susceptible to these pathogens. The present review synthesizes the existing knowledge of the world and regions on the citrus phloem-associated diseases with specific emphasis on the issue of pathogen diversity and disease development and its increasing menace to the citrus production in Pakistan and South Asia. There is a focus on disease drivers to facilitate proper surveillance and diagnosis, and combined management plans.
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Copyright (c) 2026 Muhammad Awais Fareed, Arslan Tahir, Awais Mutti, Memoona Imdad, Sammia Iqbal, Muhammad Arslan Mushtaq, Khubaib Shakoor, Talha Riaz (Author)
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