Previsual symptoms of Xylella fastidiosa infection revealed in spectral plant-trait alterations

Plant pathogens cause significant losses to agricultural yields
and increasingly threaten food security1, ecosystem integrity
and societies in general2–5. Xylella fastidiosa is one of the most
dangerous plant bacteria worldwide, causing several diseases
with profound impacts on agriculture and the environment6.
Primarily occurring in the Americas, its recent discovery in
Asia and Europe demonstrates that X. fastidiosa’s geographic
range has broadened considerably, positioning it as a reemerging
global threat that has caused socioeconomic and cultural
damage7,8. X. fastidiosa can infect more than 350 plant species
worldwide9, and early detection is critical for its eradication8.
In this article, we show that changes in plant functional traits
retrieved from airborne imaging spectroscopy and thermography
can reveal X. fastidiosa infection in olive trees before
symptoms are visible. We obtained accuracies of disease
detection, confirmed by quantitative polymerase chain reaction,
exceeding 80% when high-resolution fluorescence quantified
by three-dimensional simulations and thermal stress
indicators were coupled with photosynthetic traits sensitive
to rapid pigment dynamics and degradation. Moreover, we
found that the visually asymptomatic trees originally scored
as affected by spectral plant-trait alterations, developed
X. fastidiosa symptoms at almost double the rate of the asymptomatic
trees classified as not affected by remote sensing.
We demonstrate that spectral plant-trait alterations caused
by X. fastidiosa infection are detectable previsually at the
landscape scale, a critical requirement to help eradicate some
of the most devastating plant diseases worldwide.