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[guest]

It should do. Obviously you'd need to remove the most infected parts and destroy them - but you'll be doing that anyway.

The problem might be that trichoderma harzanium only survives in temperatures above 12C (as far as I know) and I suspect blackspot fungal spores manage a bit lower than that.

Another product to consider is Citrofresh - http://www.citrofresh.com/product-citrofresh.php It works in a different way and is very effective if you catch the fungal infection early enough but will take some time (6 weeks+) to deal with a heavy infection. It is safe enough that you can spray it into your mouth if you're daft enough

As I mentioned earlier Systhane is about the "best" of the synthetic fungicides but if you really don't want any synthetics I would try the Citrofresh first.

[roseway]

Thanks for that. Citrofresh looks interesting. I won't touch synthetic chemicals in the garden.

[guest]

Be warned that Citrofresh is NOT cheap.

It's about a tenner a litre for the ready to use stuff, which I have my doubts about - best to get the concentrate and dilute it to a suitable strength I reckon. The ready to use stuff seems to become less effective the longer its been opened, unlike the concentrate, so I can't help wondering if some contamination is taking place.

Just as well I got 5L of concentrate as I've just discovered the place I bought it from seems to have ceased trading

Actually if you want to give the Citrofresh a try then PM me - I'm sure I can find a suitable container to send you some. The concentrate is used at 10:1* for active infections and 25-50:1 for barrier protection (which is where Citrofresh really excels) so I wouldn't have to send you that much really

It doesn't specifically mention blackspot on the container but if it can deal with fusarium, septoria and target spot I'd think blackspot could be treated too. Worth testing before shelling out for the concentrate (which only comes in 5L containers) perhaps.

*I've gone to 7.5:1 before for really bad infections

[roseway]

Thanks, I appreciate the offer, but it's probably the wrong time of the year with most of the leaves fallen off.

[guest]

The next two weeks are what I've been waiting for - ground temperatures around 0C and air temps around 4C for most of the time. Bye bye fungal spores (for now anyway). Edit - so if any remaining leaves are still infected then take them off around the middle of next week as none of the spores will be capable of fruiting after a week or so of frost.

If you need it next year then give me a shout

[kitz]

btw rizla

The washing up liquid did appear to do the trick and I havent had to do anything since.
Will have to wait till next year now to see what happens ... since the leaves obviously all fell off anyhow last month.

[guest]

The problem with the washing-up liquid "solution" is that it only works once you have mould (it was mould wasn't it?). Citrofresh - and some other "organic" products can act as a barrier to mould/fungal spores etc.

Ultimately of course the problem is environmental and unless you alter the environment then it'll recur time and time again.

eg Eric has blackspot on a rose outside the front door. From that I deduce that :

a) Eric lives somewhere away from lots of traffic - air pollution suppresses some fungal spores and blackspot is one that it suppresses VERY well;
b) The rose tree is exposed to the prevailing wind;
c) The rose tree probably gets very wet on one side (backsplashes from house/guttering usually) and that is the side the infection starts.

How did I do Eric?

[roseway]

2 out of 3 probably (I'm not sure about the prevailing wind). One of the first gardening things I noticed when I moved here in the Kent countryside from North London was how much more trouble I had with fungus diseases. Rust is so common that parts of the garden sometimes look orange instead of green.

To be honest, I'm a very reluctant gardener these days. I've planted my garden up with hardy shrubs and I do little more than prune them and put up hanging baskets in the summer. But it's very wildlife-friendly, and I get loads of birds and bees.

[guest]

I can't remember whether its increased levels of carbon monoxide or ozone that tends to suppress fungal spores - I think it may be ozone - but its one of the few (gardening) benefits of living in heavily urbanised areas.

If you can prevent/reduce the backsplash and/or get some decent airflow around the wet side you should find you'll have much less fungal spores actually getting into the plant.