Is there a difference between early and late blight in the effect they have and the long term condition of soil etc. Had a look at various sites and cannot make my mind up ??? Think I might have a bit of blight in my Rocket potatoes. It has not affected the potatoes I have liftedn but plants are looking very sick. Needless to say, their condition is deciding their order of lifting.
Do the following symptoms describe your Rocket?
The plants wilting in the heat last week and the week before
The top foliage revived after the rain
Older (lower) foliage badly yellowed, some with brown margins, and some dying off
Lower parts of some stems rather pale or yellowish
Plants generally looking thoroughly tired
If so, then provided that you can not see any dark round patches on the leaves or stems, your Rocket are almost certainly suffering from the effects of the recent heatwave and the dry weather which preceded last weekend`s rain. Mine are exactly the same and so are many more that I have seen in the last few days. Quite simply, the plants are starting to die off a little earlier than usual, but they should struggle on for a bit longer yet if we don`t get another heatwave and drought.
However, if you do find round dark brownish, purplish or blackish patches on leaves or stems, then it is almost certainly blight
And no, neither blight will not affect your soil per se. Late blight is far more damaging to Solanaceae, if only because the conditions necessary for it to persist tend to last longer, than early blight (they are in fact two fungi from entirely unrelated species but are just called blights because the symptoms are similar).
 Without rigourous hygenie however the long term effects of either can be devastating (think Irish potato famine). It is most important that all infected plant material is removed completely (as in bin, not compost) as this will act as an infection source in succeeding years. This also applies to other susceptible sp. of Solanaceae in your immediate vicinity- deadly nightshade, for instance, is a symptomless host.
Better correct myself before anyone else: yes, I am aware that late blight is no longer classified as a fungus, old habits die hard.
Thanks John - that has cleared it up. Unfortunately I do have brown roundish shapes on the leaves but not of the underneath lesions.
we had blight on our first earlies, took off all the foliage completely and binned it, even off the plants that looked healthy, hopefully didn't have a chance to spread. This was before the main heatwave, but when it first got hot and wet. All the tubers are fine! (and yummy) and our seconds and mains all look fine (besides one dubious looking plant we also took the foliage off of).