Field experiments for the containment of the spread of Xylella fastidiosa in olive orchards

The control of plant diseases caused by insect-vectored pathogens relies primarily on
effective strategies for the reduction of the vector populations. The emergence of the insectvectored
bacterium Xylella fastidiosa in southern Italy, and more recently in different EU
Countries, called for research on the characterization of the xylem-feeder populations and
identification of candidate European vectors. Surveys identified the spittlebug Philaenus
spumarius as one of the most abundant species, in different countries and crops, as well as
the predominant vector spreading the infections on olive trees in southern Italy. This finding
called for the development of control strategies to reduce the population of this highly
polyphagous and widespread insect species. Besides, supporting actions for the mechanical
control of the ground vegetation to effectively reduce the juvenile populations, there was a
need to develop tools for the control of the adults. From 2015 to 2017, several formulations
based on different active substances (chemical and organic) with different mechanism of
action were tested for the control of nymphs and adults of P. spumarius. Indeed, in the last
two years, experiments were carried out, for evaluating the reduction of the bacterial
transmission rates upon applications of kaolin on olive canopies. Applications of insecticides
showed that among the synthetic products, neonicotinoids and pyrethroids yielded the
highest mortality rates and persistence, both for the control of the juveniles and adults,
whereas lower efficacy was recorded for the natural and inert compounds. Reduction of the
transmission rates have been so far detected upon applications with kaolin.