Crop rotation will help to reduce the incident of disease.
Tomatoes and potatoes are more likely to be infected by the fungus in wet, warm summers. Remove and burn any infected foliage.
Blossom End Rot
Tomatoes, peppers and courgettes. Water heavily less often rather than a sprinkling of water every day.
Brassicas grown in pots and then transplanted help to reduce this. However, I don't buy or accept brassicas from other people as you never know if you may be unwittingly introducing the fungus into your plot.
We try to water in the morning rather than at night which helps to reduce this. Remove leaves that are infected to contain the spread.
Leeks, onions and garlic. Remove infected leaves, rust doesn't kill the plant but reduces its growth.
Potatoes but can infect parsnips and beetroot especially in hot, dry summers. Water regularly in the morning.