Pseudomonas cichorii

Introduction

Bacterial leaf blight caused by Pseudomonas cichorii is a significant disease affecting many crops and ornamental plants. Here’s an overview of this pathogen and its impact. 

P. cichorii has a broad host range and has been reported in numerous countries:

• Ornamental Plants: Chrysanthemum, Gerbera, Monstera adansonii, Calceolaria hybrida (pocketbook plant), aglaonema (Aglaonema spp. Schott), and more
• Medicinal Plants: Pinellia ternata (Banxia)
• Vegetable Crops: Romaine lettuce, butterhead lettuce, escarole, perilla, basil, sage

The pathogen has been reported in various locations, including:

• Hawaii, USA –  100% of variegated specimens of Monstera adansonii were infected in a nursery
• China – A 35-40% incidence rate was observed in a 4-ha field of Banxia
• South Korea – approximately 30-50% incidence was reported in perilla fields in South Korea
• New Jersey, USA – outbreak on sweet basil during the summer of 2018, and it was also observed on mature romaine leaves and escarole
• Belgium – outbreaks of midrib rot have increasingly threatened greenhouse butterhead lettuce since the mid 1990s
• Taiwan – 20% of the plants exhibited symptoms in a nursery on December 2022

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Symptoms

The symptoms of bacterial leaf blight caused by P. cichorii can vary depending on the host plant but generally include:

• Yellow chlorotic lesions that progress to greyish-black and brown necrotic lesions
• Water-soaked edges and irregular lesions
• Vein necrosis in some plants, such as perilla
• Mid-rib rot, Leaf spots, and necrosis in lettuce varieties

Transmission and Spread

P. cichorii can spread through:

• Water droplets from irrigation systems
• High humidity and increased leaf wetness

Control Measures

Several control strategies have been suggested for managing bacterial leaf blight:

1. Resistant Varieties: 
   • For example, the use of tolerant chrysanthemum varieties such as Puspita Nusantara, Puspa Kania, and Dwina Kencana
2. Early detection:
   • Using lab methods to confirm symptoms
   • Irrigation water is suspected to be the primary source of inoculum in greenhouse settings
3. Cultural Practices:
   • Removing infected leaves
   • Watering plants strategically to reduce leaf wetness duration
4. Chemical Control:
   • Application of synthetic bactericides containing hydrogen peroxide and peroxyacetic acid

Must Read:

• Compatibility of antagonistic bacteria in controlling bacterial leaf blight (Pseudomonas cichorii) in chrysanthemum https://www.actahort.org/books/1334/1334_22.htm 
• First report of bacterial leaf spot caused by Pseudomonas cichorii on Monstera adansonii in Hawai’i, USA https://pubmed.ncbi.nlm.nih.gov/37700479/ 
• First report of Pseudomonas cichorii causing bacterial leaf blight of pocketbook plant (Calceolaria hybrida) in Taiwan https://pubmed.ncbi.nlm.nih.gov/38587801/ 
• Pseudomonas cichorii causing leaf spot disease on Banxia (Pinellia ternata) in China https://pubmed.ncbi.nlm.nih.gov/35442052/ 
• First Report of Pseudomonas cichorii Causing Bacterial vein necrosis on Perilla Plants [ Perilla frutescens (L.) Britton.] in South Korea https://pubmed.ncbi.nlm.nih.gov/35700520/ 
• First Report of Pseudomonas cichorii Causing Bacterial Leaf Spot on Romaine Lettuce (Lactuca sativa var . longifolia) and Escarole (Cichorium endivia) in New Jersey https://pubmed.ncbi.nlm.nih.gov/34236210/ 
• Development of a real-time PCR assay for Pseudomonas cichorii, the causal agent of midrib rot in greenhouse-grown lettuce, and its detection in irrigating water https://bsppjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3059.2010.02388.x
• Bacterial Leaf Blight Disease (Pseudomonas cichorii (Swingle 1925) (STAPP 1928) in Chrysanthemum (Dendranthema grandiflora Tzvelev) and Its Control) in Indonesia https://www.researchgate.net/publication/347620431_Bacterial_Leaf_Blight_Disease_Pseudomonas_cichorii_Swingle_1925_STAPP_1928_in_Chrysanthemum_Dendranthema_grandiflora_Tzvelev_and_Its_Control_in_Indonesia

David Santos is the CMO of Healthy Hydroponics InnoTech