It's not a pathogen that I am working on but this is a good example to illustrate the importance of research in plant pathology. Here is a news article from the BBC about a new wave of bacterial infections on horse chestnut trees in the UK caused by Pseudomonas syringae pv. aesculi. The article offers little information about the pathogen or why it has suddenly become a problem. Confusingly the article mentions two other problems facing these trees, an insect pest (moths from Greece) and a fungal pathogen causing leaf blotch, which are separate problems but may be interlinked with the outbreak. For example it is possible the bacteria was introduced by an insect vector or that the moths and fungal infections rendered the tree more susceptible to the bacterial infection either through stress or wounds.
I am currently taking a plant disease diagnosis class in which we have been learning how to systematically diagnose plant problems and their causes. Each week we are given an unknown plant sample and we are to fill in a diagnosis form for it. This involves identifying the host plant, understanding the pattern of the problem on the plant or plant part and in the environment around the plant such as the whole field or wherever the plant was collected from. Then looking at the symptoms and signs of any pathogens or pests or clues to environmental or human issues causing the problems.
One of my samples in this class was a branch of a cherry tree with severe gumming (bleeding cankers). I sucessfully isolated Pseudomonas syringae pv. syringae from a canker and cultured it on Kings B agar. This media provides specific nutrients which Pseudomonas species can utilise to make a pigment which glows under UV light. This is a rather simple and fun diagnostic tool for diseases caused by P. syringae.
This disease on horse chestnuts is of interest as it bears resemblance to epidemics of Dutch Elm Disease, Eastern Filbert (Hazelnut) Blight and Sudden Oak Death which are other diseases which also threaten or have devastated trees populations over wide areas in the past. Management of plant diseases on forest hosts such as these trees is rather different to management of diseases on annual crops for example. The epidemiology of these pathogens varies according to factors of the disease triangle (HOST-PATHOGEN-ENVIRONMENT). For disease to occur there must be a virulent pathogen, a susceptible host and conducive environmental conditions. The spread of this epidemic on horse chestnuts will depend on the mode of pathogen spread, the availability of susceptible host trees and management practices in use.
I could go on about the history of the tree diseases I mentioned and the importance of understanding the pathogens and their mode of spread and the conditions they require but I will save that for another day. I'll be taking a forest insect and disease management class in due course and also a forest pathology class so then I'll be bursting with more fascinating stories to tell you!
I am currently taking a plant disease diagnosis class in which we have been learning how to systematically diagnose plant problems and their causes. Each week we are given an unknown plant sample and we are to fill in a diagnosis form for it. This involves identifying the host plant, understanding the pattern of the problem on the plant or plant part and in the environment around the plant such as the whole field or wherever the plant was collected from. Then looking at the symptoms and signs of any pathogens or pests or clues to environmental or human issues causing the problems.
One of my samples in this class was a branch of a cherry tree with severe gumming (bleeding cankers). I sucessfully isolated Pseudomonas syringae pv. syringae from a canker and cultured it on Kings B agar. This media provides specific nutrients which Pseudomonas species can utilise to make a pigment which glows under UV light. This is a rather simple and fun diagnostic tool for diseases caused by P. syringae.
This disease on horse chestnuts is of interest as it bears resemblance to epidemics of Dutch Elm Disease, Eastern Filbert (Hazelnut) Blight and Sudden Oak Death which are other diseases which also threaten or have devastated trees populations over wide areas in the past. Management of plant diseases on forest hosts such as these trees is rather different to management of diseases on annual crops for example. The epidemiology of these pathogens varies according to factors of the disease triangle (HOST-PATHOGEN-ENVIRONMENT). For disease to occur there must be a virulent pathogen, a susceptible host and conducive environmental conditions. The spread of this epidemic on horse chestnuts will depend on the mode of pathogen spread, the availability of susceptible host trees and management practices in use.
I could go on about the history of the tree diseases I mentioned and the importance of understanding the pathogens and their mode of spread and the conditions they require but I will save that for another day. I'll be taking a forest insect and disease management class in due course and also a forest pathology class so then I'll be bursting with more fascinating stories to tell you!
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