Scientists in The Netherlands have developed a sensor that could eventually be used to detect damaging cereal crop diseases, such as septoria, before they can be seen by the naked eye.

A team of plant pathologists at Wageningen University has developed the Crop Health Sensor (CHS) which uses spectral reflectance analysis to show early disease levels in leaves.

Apple leaves of different cultivars were infected in the laboratory with apple scab (Venturia inequalis) and evaluated. Results showed a difference in reflection between healthy leaves and infected leaves and enabled diseased leaves to be distinguished after several hours.

“We inoculated trees and measured the reflection of light at two, four, six and eight hours after picking leaves and we noted the differences between newly-opened leaves on the top and older leaves down the branch,” said lead scientist Jan van de Zande.

“By using the sensor, we were able to see infection just four hours after inoculation – when normally it would take us 10 to 12 days by the naked eye.”

This season, the team had extended the trial into the field so that wavelengths could be assessed in the orchard to see if disease symptoms could be properly identified, he added.

By adapting the sensors, dose and timing of chemicals could be determined based on crop health, said Mr van de Zande.

The five-year study could also see the development of sustainable spraying techniques, such as sprayer that automatically adapt to disease levels, giving more precise applications where it is needed.

Syngenta application specialist Tom Robinson said: “If we could use sensors to show early symptoms of yield-robbing diseases, such as septoria, mildew and rusts, we could adapt our crop protection strategies and reduce overall pesticide use.”