Phytophthora infestans is the fungus responsible for Blight and can affect both Potatos and Tomatoes alike - brown patches develop on the leaves, and the fruits of the tomato start to go brown in patches until the whole fruit shrivels and unless the affected leaves of potatoes removed in time, the fungus will get into the soil and wipe out your whole potato crop as it did in Ireland (although maybe on slightly smaller scale!). The fungus seems to strike predominantly in moist or wet weather in mid to late summer and does not take long to take hold.
- Try operating a good crop rotation system which helps avoid pests and diseases getting established.
- Ensure the plants are correctly spaced out.
- For potatoes; earth up the tubers well - this will offer greater protection for your crop.