Potato blight:

The most important crop residue to eliminate to help to prevent infection in the following year is the potato tuber itself. It is very common when digging potatoes to miss a few tubers, especially the tiny ones. These could well be infected with the blight fungus and create a source of infection in the following year. You can never guarantee to get them all, but you should try. If you see any potato plants emerging in the row where you grew them last year, dig them out straight away. This will also help to protect against early virus infections spread by aphids – a virus-infected crop often dies early and produces lots of small tubers as a result, which will then contain viruses which can be picked up by aphids from the new plant produced the following year and spread to the new crop.

The other thing to do in relation to blight is to choose to grow some of the new Sarpo varieties now available, which have been bred in Hungary specifically for resistance to potato blight. If you put “Sarpo” into Google you will find a lot of sources of these new varieties, which really do resist infections. A word of warning though - diseases have a habit of mutating to overcome inbred resistance, so they may not stand the test of time, but should certainly be good for a few years.

Blackcurrant reversion virus:

As stated, this virus is spread by the big bud mite. It results in the crop diminishing to a negligible quantity. As soon as you see big buds on a bush, prune off that twig or branch and dispose of it.  It may be that the virus won’t have spread very far from the mite-infested buds, but this cannot be guaranteed. So then examine the flower buds elsewhere on the bush. Virus-infected parts of the plant produce flower buds that are much less hairy than normal. (A good website on which to see this is http://www.ars-grin.gov/cor/ribes/ribsymp/reversion1.html ). If much of the bush is like this, eliminate the whole bush as soon as possible.