Sick plants, your drone doctor will see you now
If you want to stop plant disease in its tracks, it’s essential that the damage is diagnosed as quickly as possible. To do that, you can take to the air.
Spotting crops or woodland that are suffering from damage or disease from ground level is notoriously difficult because there’s just so much stuff in the way — after all, there’s whole idiom dedicated to extolling the difficulties of seeing the wood for the trees. It makes sense then, if you want to survey a forest for signs of disease, that you take to the skies and adopt that ‘bird’s eye view’.
To achieve this, a UK research team are using drones and a technique originally developed for earth observation, called hyperspectral imaging, to diagnose damaged plant life faster than has been possible up to now.
Over 3 million hectares of the UK are covered in woodland, approximately 13% of the nation. However, with climate change and non-native pests and diseases on the increase, the UK’s iconic woodlands are now facing unprecedented challenges. But, with the team’s groundbreaking use of imaging technology, hope is hovering on the horizon.
When spectral imaging goes hyper
Hyperspectral imaging (HSI) is a technique that, rather than just assigning the usual boring old primary colors (red, green, blue) to each pixel on its sensors, instead analyses a wider spectrum of light. The light striking each pixel is broken down into many different spectral bands in order to provide more information on what is imaged compared to basic optical imaging.
Led by the Science and Technology Facilities Council’s (STFC) RAL Space, the UK research group have collaborated to combine publicly-available cameras with imaging techniques originally developed for Earth observation research, to revolutionise the monitoring of the composition and condition of the UK’s woodlands.
Eyes in the sky
These aren’t any of your common or garden drones that you might pick up from your local electrical emporium either. Sporting as many six rotors, and boasting an up to two-metre wingspan (depending on the drone used), they have the power and stability needed to survey hundreds of acres of wood or farmland. The drones were deployed in Suffolk in 2022 and 2023 during the summer months when plant growth, and thus disease proliferation, are at their peak.
One such disease that can be detected with the drones is ‘Ash dieback’, a devastating fungal infection, originally hailing from Asia, that has caused widespread damage to trees in the UK in little over a decade since its accidental introduction to the landscape.
By using hyperspectral imaging to determine the health of our trees and sharing the data with tree wardens and local councils, those tasked with care of our nations flora they can make better informed decisions and, hopefully, better plans for preserving our woodlands.
To determine whether a plant or a tree is healthy or not, data gathered across visible and infrared light wavelengths, are compared. Typically, plants have low reflectivity in visible light, but this increases dramatically when wavelengths are bigger than 700 nanometres (red light).
This data is then translated to a map that shows how well the tree reflects varying wavelengths of light. Deviations in the amounts of light that the plants are reflecting from the expected pattern could be an indicator of potential stress or health issues.
Led by RAL Space’s Dr Michelle Hamilton, the project was funded from STFC Horizons Programme ‘Solutions to Net Zero Call’, which promotes the use of innovative scientific techniques to assist in the UK’s broader aspirations to achieve Net Zero.
Curbing wheat loss
Moving from woodland to farmland, Dr Melina Zempila, an atmospheric physicist based in RAL Space, is using the same technology to protect wheat, a staple ingredient that sustains millions worldwide, from the crippling effects of diseases such as a fungus called rust.
Despite its relatively innocuous name, rust is fast-spreading fungus that can tear through wheat growing regions leaving a trail of devastation in its wake. In the past few years alone, rust has left more than 10 million tonnes of crops being unfit for consumption.
Using the hyperspectral imaging technique, Dr Zempila’s team can spot a rust infection at an early enough stage in the crop’s growth cycle, that lower volumes of pesticides are needed to bring the infection under control and more of the crop can be saved. By minimising the risks of water and soil contamination, this approach not only protects the crops but also contributes to sustainable farming practices.
A team effort
Although led by RAL Space, it was the collaboration with colleagues from Newcastle University and Fera Science Limited — in the case of the woodlands project — and the National Institute of Agricultural Botany (NIAB) — in the case of the crops study — that made the twin projects possible.
The collaboration enabled the combination of static and aerial imagery with cutting-edge image analysis techniques and drone technology. By combining engineering experience, calibration and implementation, and data analysis techniques the team were able to cover all aspects of research in this project.
Recent advances made in imaging technology pioneered by the RAL Space team are enabling both a positive development in our safeguarding of UK woodlands and helping to enhance the security and sustainability of global agriculture.
Story by: Jake Hepburn, Ben Gilliland. Video by: Ky Trickett
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