preventing disease next tear

[beckybee]

For the last couple of years my plot has suffered from Anthracnose (in the loganberries), rust (leeks, onions and garlic) and blight. Is there some way of treating the perennial plants and the soil to reduce the chances of this happening again? Being fungal diseases I assume they'll just lie dormant over the winter and then come back and get me again next year? Would bordeaux mixture do it?

[PAULW]

I think I remember the tutor at college saying if you have anthracnose dig it out and burn the plant and dont plant the same plant back in that place as it will only affect the same species.