Wet, wet, wet…

Wet, wet, wet…

After a few pieces of frivolity, time for some serious Bonsai.

For those of us “lucky” enough to live in the UK, we have been experiencing some of the most wonderful weather.  Low temperatures, the wettest april in 100 years and no sign really of it improving.  Not only is this affecting the growth of out trees but it is also the ideal conditions for fungal problems.

Compared to Japan we are lucky in that our trees are relatively untouched by bugs, pests etc.  Whereas in Japan spraying pesticides and fungicides was a twice monthly, sometimes weekly event; in the UK it can be once a year if we are lucky. This means that amongst most enthusiasts generally vigilance is low and it is not something which is always on my mind.

Over the last year or two I have noticed a few fungal problems attacking pines in particular.  Looking at the Forestry Commission website, we see…

Red band needle blight

Red band needle blight causes needle defoliation which, in severe cases, may kill trees. Over the past two decades the incidence of this disease has increased dramatically in Britain. The increase could be due to a rise in rainfall during spring and summer and warmer spring temperatures which encourage spore dispersal and infection. Climate change may increase outbreaks if warming trends continue.

There are a few problems which can affect even the hardiest of pines, however there are steps we can take to prevent fungal problems…and as with most things, prevention is better than cure, because once a tree is infected, it is impossible to cure that year.  Infected needles will not go back to health like they will with some insect damage.

Prevention measures

Keeping foliage dry : Do not spray the foliage of your pines during times of high humidity and never during the afternoon/evening.  The lowering evening temperatures and moist conditions are ideal conditions for fungal spores.  The water droplets also provide a dispersal mechanism and the spores from one branch can soon spread to the rest of the tree.

Keeping foliage well ventilated :  Particularly a problem for trees in polytunnels and greenhouses.  Insufficient airflow will lead to high humidity causing germination and then easy dispersion of fungal spores to all your healthy trees.

Remove diseased foliage:  Remove foliage that has been affected and burn it (or put it in the recycle bin) and then sterilise your tools.  Those black spots you see are the spores waiting to burst out and spread to your other trees.  Laziness will spread disease.

Spray fungicides :  Prevention rather than cure.  Spray a recognised fungicide during the growth phases of the tree, start once the temperature has gotten to around 12 C and continue once every two/three weeks until the growth has finished and needles have hardened off.  And then once more for good luck.  Rotate several fungicides rather than use just one.


Location in garden :  Heavily diseased trees should be immediately quarantined, taken away from the healthy ones but not so that it is kept in a location where it will deteriorate further.  Some diseases jump from tree to tree, others use another tree to incubate so keep your Junipers and Hawthorns separate.  Juniper Hawthorn rust is a problem which is easily solved….by keeping them apart.


Keeping the tree healthy:  A stressed tree is more susceptible to disease and so keeping trees healthy is essential.  Boost health by giving trees fertiliser and also things like seaweed extract, HB101 etc.  Things with trace elements and auxins that will boost growth, give healthy foliage and hence improve the “immune system” of the tree.


Sadly due to the vagaries of Defra/EU legislation we are hamstrung by a lack of effective chemicals off the shelf but there are a few available.  Systhane and This copper based fungicide are available.  Also classic old school Bordeaux Mixture and Scotts Fungus Clear

I don’t have shares in any of the above companies, they are all that are available.  It is best to have them all in your armory and to rotate them.  Each has a different active ingredient which will affect the fungal cells in different ways.

Spraying should be done on a windless cloudy day (ideally).  Direct sunlight to be avoided at all costs as the chemicals are photosensitive and will break down in direct sunlight.  Mask/gloves/covering skin is essential.  Ever wonder why the children of most Japanese Bonsai artist are girls?  A small amount of fungicide on the surface soil of your pot is not a problem, but avoid getting it in the soil or your friendly fungus will also die.  DO NOT GIVE THE TREES A FUNGICIDAL BATH!

Given the weather we have been having, take the first opportunity you get on a dry and still day to get out there and protect your trees.

Well, all this talk of fungus hasn’t left me mush room to congratulate one of my all time heroes, well done Ronnie O’Sullivan…a snooker legend, a man touched equally by natural genius and natural fallibility.  A master who has the ability to perform at levels beyond our ken.  Seems happy in his life for once.

2 Comments

  1. bonsaieejit.com 3 years ago

    Just as Rocket Ronnie hits form, he announces that he's taking 6 months off to spend time with his kids! Gotta love him for that.

    Oh, and this was probably the most serous post I've read from you ;-)Thanks for all the info Trev.

  2. Serious until you Capped it off with a bad shroom pun. Grow up Peter:-)

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