We have a large tunnel at Henfaes for growing tomatoes and potatoes. This year the tunnel has remained free of blight despite its closeness to a large trial of blighted tomatoes planted outside. But a couple of weeks ago, spores from the trial infected some plants in the tunnel and produced the most spectacular blight I have seen in a while. Sporangia of Phytophthora infestans have formed in very large numbers and are highly visible as a silvery frosting to the dying leaves and stems. It is interesting that the fruits (cultivar Sungold) are mostly healthy. Beware not to allow the pathogen into your tunnels or greenhouse.