GAGLIANO DEL CAPO, Italy, July 31, 2019 (BSS/AFP) – Working in an arid
Italian field of crumbly soil, agronomists are battling a rampant bacterium
that has already infected millions of olive trees and could threaten the
entire Mediterranean basin.
Xylella fastidiosa, which has no known cure, has devastated ancient olive
trees in Italy’s southern Apulia region and beyond, causing 1.2 billion euros
($1.3 billion) of damage to the world’s second olive oil exporter after
Spain.
Since 2013, the disease has torn through Apulia’s olive groves, leaving
thousands of skeleton-like trees in its wake, and little hope for farmers.
Once Xylella fastidiosa bacteria — carried by tiny sap-sucking insects
known as spittlebugs — take hold, blocking the tree’s ability to absorb
water, the plant is doomed.
– Bureaucracy and ‘mafia’ –
The only way to fight the spread of the disease, known as “olive tree
leprosy”, is to destroy diseased trees, but farmers must seek special
permission and say the authorities are not always forthcoming.
Doubtful of conspiracy theories that the mafia are killing trees to make
way for hotel construction, agronomist Pierfederico La Notte noticed that
some trees seemed not to become infected, standing tall and green in
otherwise devastated fields.
Suspecting that they may be resistant varieties that can develop the
disease to a small degree but continue to grow and flower, the soft-spoken
researcher rapidly identified two that appeared to suffer little from
Xylella.
“The Leccino and Favolosa varieties are a starting point, not the finish
line,” said La Notte, who works for Italy’s National Research Council.
“We hope, and we’re working on it, to find a much bigger number of
resistant varieties,” said La Notte, teaching visiting Egyptian agronomists
in a research field outside the ancient town of Gallipoli.
Results so far are promising.
Branches from resistant varieties that are grafted onto the trunks of sick
trees are growing perfectly and even producing fruit, offering a glimmer of
hope to the devastated region in the heel of Italy’s boot.
– Immunity? –
Down the road in the heavily agriculture-dependent region, agronomist and
olive oil producer Giovanni Melcarne has lost 90 percent of his plants since
Xylella arrived, and he is seeking an even better solution: immune varieties
of olive tree.
While much of his machinery for olive cultivation now lies dormant, he has
built an improvised greenhouse, filled with dozens of small olive saplings,
among which he hopes to find at least one immune variety.
“We will infect them with the illness, we will contaminate them with the
insects that transmit the illness so we have scientific proof that this
plant, this indigenous variety that we could cultivate, doesn’t catch the
disease and so is immune,” Melcarne said, carefully labelling a batch of
olive saplings.
But it will be at least another year before the results are known, given
the slowness with which the disease will become visible after infection,
something that has helped it spread invisibly, and rapidly.
Drones using infrared cameras can help detect the infection marginally
earlier, but the disease’s progress is relentless.
Known in the United States as Pierce’s disease, it devastated California
vineyards in the late 19th century.
The European Commission describes Xylella as “one of the most dangerous
plant bacteria worldwide, causing a variety of diseases, with huge economic
impact for agriculture, public gardens and the environment.”
Since it arrived in the Apulia region in 2013, probably from Costa Rica
according to the Italian farmers’ union Coldiretti, the microscopic pathogen
has killed more than a million olive trees in Italy.
– Mediterranean spread –
Coldiretti said earlier this month that Xylella has infected 21 million
trees, and is “spreading inexorably north at a speed of more than two
kilometres (over a mile) a month”, leaving behind it “a ghostly landscape”.
The bug has also attacked orchards in Spain, France and now Iran. Both
Greece and Portugal are bracing for its likely arrival.
Some 350 plants are vulnerable, including grape vines, citrus and almond
trees.
Scientists say there is a real risk the disease will spread to the entire
Mediterranean basin, where olive oil is a staple in the diet and vital to the
economy.
This is why the International Center for Advanced Mediterranean Agronomic
Studies (CIHEAM) in Bari, Apulia’s capital, has decided to train agronomists
from around the region, including the Middle East and North Africa.
– Relentless advance –
“Today’s technology lets us upload photos in real time, images of symptoms
to help and also, through the project, we can mobilise the scientific
resources of European countries which can go to other Mediterranean countries
to help and to train these people,” said CIHEAM agronomist Maroun El
Moujabber, from Lebanon.
Budding and experienced experts from around the Mediterranean study at
CIHEAM’s sunny campus, where an app has also been developed which allows
olive farmers or anyone else to input symptoms as they observe them,
hopefully providing a better indicator of the disease’s spread, and how to
slow it.
Arafat Hanani, a young Palestinian doctoral student and plant pathologist
at the CIHEAM, says that while “nothing is impossible about science”, Xylella
is particularly problematic.
“The rule about Xylella fastidiosa is that it’s a fastidious bacteria…
it’s not easy to control, it’s not easy to manipulate it,” he warned,
returning to his microscope in search of a solution.