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  Gareth December 5, 2015 at 12:09pm

  The fungi causing box blight are Cylindrocladium buxicola and Pseudonectria buxi – these fungi are themselves the pathogens (ie disease causing organisms). For example the mushrooms of honey fungus are just the visible fruiting bodies of an extensive hidden body of the whole fungus. Honey fungus is a pathogen because it causes disease. Field mushrooms aren’t because they are tasty. The small blister like fruiting bodies of the various box blight fungus are most active in warm wet conditions (I’ve certainly noticed a lot of blight this autumn) and it is these conditions that are favourable to the fungal disease (pathogen) being transmitted. Cutting box leaves in these conditions helps the disease to spread through open wounds. The fungus will persist (alive) in the woody tissue of the host plant long term even when not fruiting. Cultural techniques such as timing of cut, use of herbicides can manage the impact of the disease but it will be persisting in the living tissue of its host until a suitable environment occurs for it to spread. It can be pretty virulent when it does but more anecdotal stories are being heard about manging the disease before removing the host plants.

  As far as I know there is no fungicide available that will kill either of these box blight species, though research is going on all the time. The fungicides that are available are a cocktail that only suppress the symptoms of the disease and are only licensed for use in the nursery trade. I don’t think any fungicide is licensed for use in amenity situations. Though off-label licensing can be applied for?

  I’ve taken to cutting box on the winter months recently, whilst the fungus is in theory dormant and won’t spread.

  Hope that adds to Toms explanation!?
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    dan > Gareth December 5, 2015 at 5:04pm

    Both comments help a great deal - thank you 

    Ive done the chemical research as you mention and there are some very helpfull people out there -- two replied to my earlier chemical box blight issues and were very helpfull by mail also. 

    Problem is as you say -- treatment appears so early stage that presently containment and prevention are the best results - Ive recently spoken to a proff sprayer who has stated hes been using such fungicides on certain properties for three years and although he has achieved i suppose a containment there is no erradication. 

    On top of the fact some people think the chemicals destroy the plants natural defense systems 

    Whats confused me as ive looked into more is that box blight appears to be a highly temp sensitive pathogen and is effectly killed at freezing and at over thirty five degrees cel 

    In which case it sounds an easier pathogen to kill than others that arent so sensitive 

    So in a massive frost -- minus fifteen for example over several days -- the box plant and roots in smaller pant cases must completely freeze ? -- Therefore all of the pathogen should be subjected to this ? hence death 

    This years outbreak is very bad from what i can see and we can only assume weather will get worse for its spread coming years 

    A lot of the info i can find is sketchy and a lot outdated -- and even the most experienced gardeners i can talk to seem at a loss with the topic 

    Actually as you mention a serious box pruner stated the same -- he only cuts in cold months now 
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  Agrigem - Sarah Kimm December 7, 2015 at 10:47am

  Morning Dan,

  Just to add a little to the already comprehensive replies!

  A pathogen is anything that causes disease or infection, so can be a bacteria, fungus or a multitude of other organisms.

  There are 2 fungi involved, C. buxicola and P buxi and the visible symptoms are the blight that we see.

  The spores are the way that the fungus will survive away from the host plant and when they are transferred to the Box plants, (inoculation) they can germinate within a few hours and then you will see the chlorosis starting a week or so after that.

  The 2 fungi are both affected by temperature, but this is high temperature rather than low, so they are usually killed off by temperatures over 30 degrees C, but will be unaffected by frosty conditions.

  As to control of the disease, I obviously sent you the program that we have come up with that contains both cultural and chemical methods to control the problem. What this contains is plenty of nutrition and the thinking behind this is that a healthy plant is far more likely to fight the disease off. This is then combined with a fungicide program that includes Signum which is a systemic, protectant and curative fungicide that has approval for Amenity Vegetation as an EAMU on it.

  I hope this helps, but if there is anything else, please come back to me and I will do my best to help you out.

  Cheers Ollie

  ollie.wright@agrigem.co.uk
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  dan December 12, 2015 at 1:44pm

  Ollie cheers once again 

  So would prolongued exposure to plus thirty degrees kill the fungus / pathogen throughout the whole plant ?

  Having worked in greenhouses before im aware plants will handle well over that temp as long as they have adequate water and/ or humidity 

  If this was the case wouldnt commercial growers be able to subject plants to this prior to sale etc 

  And wouldnt areas that have regular plus thirty degrees summers /south Europe / USA etc have zero outbreak -- or at least erradication in those areas prior to poss re infection 

  I guess same point im confused with -- why does extreme cold or hot not kill the fungus within the plant ?