Spotting tomato blight with a smartphone

A smartphone-based sensor that can be used to detect microbial infections in tomato plants is described in a study published online this week in Nature Plants. This system could help fight crop-damaging diseases by identifying them at an early stage.

Plant diseases cause around 20 - 40% of crop losses. Late blight is caused by the microorganism Phytophthora infestans, which rapidly infects tomato and potato plants and kills them within days if left untreated. In favourable weather conditions, it spreads rapidly and can lead to pandemics. Most notably, P. infestans caused the Irish potato famine in the nineteenth century.

Qingshan Wei and colleagues developed a sensor that can detect late blight in tomatoes within two days of infection. The authors used chemically modified gold nanoparticles that react with volatile organic compounds produced by infected plant leaves. This reaction leads to a change in colour that is then captured using the camera of a smartphone. In a blind test, the device could detect late blight with an accuracy of 95%.

The authors found that this technology can detect late blight before its symptoms are visible to the eye, which can enable an early response to prevent the spread of the disease. They suggest that when combined with different colourimetric indicators, it could potentially be used for other crop diseases.