3D scanning in citrus cultivation to combat Citrus Greening Disease

Fraunhofer IIS is conducting research to detect Citrus Greening Disease in citrus plants at an early stage to prevent its spread: To this end, the Development Center for X-ray Technology division employs cutting-edge 3D scanning technologies for plant phenotyping.

Oranges, clementines, lemons, grapefruits, limes – citrus fruits play an indispensable role in our kitchens and diets. Yet the plants behind them face a stealthy adversary: The Citrus Greening Disease. The incurable bacterial infection, commonly referred to in technical jargon as Huanglongbing (HLB), was first identified in China and poses a serious threat to global citrus production. While HLB has not yet been detected in the EU, the insects that transmit the disease from tree to tree have already been found in Portugal, Spain, and Cyprus.

All commercially cultivated citrus plants are susceptible to HLB, which leads to premature fruit drop and significant yield losses. The progression from initial infection to plant death can span up to five years. Throughout this timeframe, further plants may become infected, underscoring the importance of early detection. Some wild citrus relatives show resistance to HLB and may hold the key to breeding resilient varieties in the future. In addition to analyzing resistant plants, detailed phenotyping of infected citrus plants is essential for understanding their responses and curbing the disease’s spread.

Non-destructive plant analysis – at Fraunhofer IIS and in collaboration with partners around the world

HLB currently poses a significant problem, particularly in Asia and South America. In Brazil, for example, nearly one-third of small-scale citrus farmers have gone bankrupt due to the disease. To address this, Fraunhofer IIS is collaborating with the research institution Fundecitrus in Brazil. The goal is to equip them with technologies such as phenotyping systems to detect infections in citrus plants at early stages, based on parameters like leaf color, shape, growth, or yield. This enables early identification and removal of infected plants, helping to slow the spread of the disease.

At the Fraunhofer IIS phenotyping facility in Merkendorf, only healthy young plants are examined. The more than 1,000 m² hall houses three controlled environments that can simulate various climate conditions, including CO₂ levels. Complementary 3D data acquisition systems – including X-ray CT and optical scanners – enable analysis of both above- and below-ground plant structures. This allows researchers to track issues such as root development disturbances. The resulting plant traits, or phenotypes, are visualized as high-resolution color point clouds.

Early detection of plant responses to HLB is vital for EU early warning systems and breeding programs aimed at identifying resistant genotypes. Traditional assessment methods are manual and time-consuming. The integration of 3D color imaging and X-ray CT technologies enables rapid and non-destructive phenotyping across diverse citrus populations. This paves the way for an early warning system to contain HLB in the EU, ensuring citrus plantations remain productive and citrus fruits continue to be available in consistent quality and quantity.

Smart Farming through phenotyping

The phenotyping facilities at Fraunhofer IIS offer a wide range of technologies to adapt to any measurement scenario across various plant genera – from stereoscopy and Laser sheet-of-light measurements to computed tomography. This extensive suite of sensor technologies opens countless possibilities for measurements involving different organisms, diseases, and environmental conditions. The result is precise, technology-driven agriculture – known as Smart Farming.