Dear Sven,

My allotment partner and I successfully grew a few different types of tomatoes on our allotment until two years ago when a tomato blight struck. The leaves of the young plants went grey and we stripped them of their green fruit before they became infected to. What is tomato blight and when will we be able to grow tomatoes again?

Thanks for your help!

Ellis

Our Gardens Expert replies:

Dear Ellis,

Blight is a fungal infection caused by warm moist conditions. The fungus is produced on tomato and potato foliage and then spreads via the wind and rain, therefore it can be washed into the soil and affect potato tubers too.

Tomatoes grown in open ground are susceptible to blight whereas those grown in the green house are less so. You will see a brown discolouration on the leaf tips that spreads. If the growing conditions are a bit on the damp side you may also see a whitish-grey fungal growth (which sounds like what you are experiencing).

The best control is to make sure not to water the plants from above (just water the base of the plant) so you don't wash spores into the soil. If you can grow tomatoes under glass they will be much less likely to get the fungus. There are sprays available that will help protect tomatoes and potatoes, try mancozeb or any copper-based fungicide and spray them thoroughly before the fungus appears. Blight is rife in damp conditions so be extra diligent when conditions suit! Crops need to be rotated yearly and the same applies to tomatoes - this makes sure that diseases don't spread around your patch and also ensures that the nutrients needed by each type of crop are not leeched from the soil. I recommend that you move your tomatoes somewhere else and grow something else in the spot - but definitely not potatoes!

Best of luck!

Sven