[jonewer]

I have a young pear tree that seems to have some kind of infection. Probably a fungus so I thought I'd make up a copper sulphate solution and spray it which I did yesterday afternoon.

Today the leaves and young shoots and covered in black spots and patches!

Oh noes. What have I done?  Is the damage permanent? I though CuSO4 wouldnt harm the plant at all!

[Yorkie]

I don't know the specific answer, but you should be aware that it has been illegal to use copper sulphate since November last year, when its licence was withdrawn ...

What made you think the original problem was fungal?

[jonewer]

Illegal? What, even in your own garden?

It seemed to be a form of canker but looked quite distinct from the bacterial canker one sees on apple trees (It seemed to have entered through a bud and infected the wood underneath, the cambium dying off afterwards). Hence I guessed its a fungus.

[Yorkie]

Yes, it's illegal full stop.  What you choose to do in your own garden is, of course, your own business ... but we do have to let people know what the rules are at least.

I've looked at a number of sites to see what you might be describing.

Wikipaedia has a list of pear diseases - though I think it is an American source.

Could it be pear rust?  The RHS page indicates that canker like symptoms can be a result.

But I'm still not sure about the answer to your main question, re. whether the tree is damaged irrevocably.  Hope not, though.

[ilan]

Can you clarifiy is Bordeax mixture still ok to use as it is a mixture of copper sulfate and slaked lime ? thanks

[Yorkie]

Can you clarifiy is Bordeax mixture still ok to use as it is a mixture of copper sulfate and slaked lime ? thanks

Yes, that's fine to buy until Feb 2013 and to use until Feb 2015.

RHS list of withdrawn pesticides

RHS document about fungicides

[DD.]

Per the RHS:

Bordeaux Mixture will be withdrawn from sale on 28 February 2013 but any person can use and store  existing stocks until 28 February 2015.

[DD.]

Both on the same track!

[Yorkie]

Both on the same track!

Or even the same RHS page! 

[galen]

So kind of on the same track (sorry for highjacking the thread) are we now only limited to the Fruit and Vegetable Disease Control (Bayer Garden) for damping off since withdrawl of Cheshunt Compound?

[ilan]

Many thanks for that was not bordeaux mixture considered "organic" for the control of blight  not sure what to use now 

[solway cropper]

I'd buy in a good stock and continue using it, but then I'm an anarchist. What you choose to do is up to you.

[JayG]

Copper sulphate only just scrapes through onto the organically approved list by virtue of being a naturally-occurring salt, albeit in much smaller concentrations than would be applied using Bordeaux mixture or similar.

Like a lot of other chemical treatments which are withdrawn, it's not at all clear whether anything else will come along to replace it (past experience suggests usually not!) 

Legality issues aside, it's never a good plan to treat a problem with a home-made remedy without having an accurate diagnosis - that's got to be a potential waste of money if nothing worse.

[mumofstig]

The Bayer spray which is also copper based says

To protect trees spray in autumn at or just before leaf fall,
repeat at 50% leaf fall. If infection is severe repeat in spring
before bud burst. Do not spray once young shoots emerge.

Did the copper sulphate not have a warning?

[Aunt Sally]

Is the damage permanent? I though CuSO4 wouldnt harm the plant at all!

I'm not sure if the damage to the plant will be permanent - it may be.  The biggest problem with using copper sulphate solution is a build up of toxic copper in soil.

The lime in Bordeaux Mixture is to prevent this pollution taking place.

And as previously said Bordeaux Mixture will soon not be a legal treatment for amateur use.