A couple of years ago we had red spider mite in our greenhouse so we put one of those killer candles in,then the oh did the usual,changed the border soil and washed all the glass.We haven't suffered since.We had blight in there last year but just did the usual, we spaced things out better and had a smashing crop of early toms and the cues are still going.On reflection I think changing the soil,if not too much of a chore,is well worth it
