What to test

Blight will first appear as blackened areas on leaves or stems. Early symptoms are often seen on the edges of leaves.  Damaged areas will be small to start with, but increase in size rapidly. 

For the test, use leaf or stem material which shows symptoms, and if possible include the junction between health and damaged tissues. Do not use completely dead tissue.  As a general guide, use a sample of leaf approximately 25mm square.  Blight CheckDS can be used with samples taken from any part of the potato or tomato plant.  If testing tomato fruit, use only the surface layer, avoiding the ‘flesh’ of the fruit.

When do I test?

Symptoms of blight are likely to appear from mid-summer onwards.  In wet years, symptoms may be seen earlier, and crops are more at risk.  Testing should be carried out as soon as symptoms are seen, and monitoring for symptoms should continue until cropping is complete