Posted: 05/09/2012 at 11:36
I have had tomato blight in the greenhouse for the last 2 years.
Can you tell me if and what treatment i should use to avoid it happening again
Unless you want to spray preventively against fungal problems, all you can do is basic housekeeping. As WD says above, ventilation is a fundamental. More the better. Air circulation is a big help against the fungal spores settling on foliage. I've known people to keep an electric fan set on low to keep the air moving.
Beyond that, keep as much space between tom plants as possible - at least 3' hopefully - and try to avoid great wads of foliage developing on plants by judicious removal of branches and leaves. The thicker the foliage, the less the air can circulate.
Never ever wet the foliage. Damp foliage is heaven for fungal spores.
Try to keep a gap of about a foot between the lowest foliage and the soil. Fungal spores can and will fall from the foliage to the soil underneath and they can splash back up again when watering. The gap helps against this.
The problem with greenhouses is that the closed environment can be an incubator for diseases. That's what you have to work against.