Xylella fastidiosa and your garden in Mallorca

Xylella fastidiosa is established in the Balearics, with more than 1,800 confirmed cases recorded across the islands by 2024. For a garden owner it matters in three places: which trees you plant, where you buy them, and what you do if one starts dying from the top down. Olives, almonds and vines are the hosts most people have in their gardens.

What is Xylella fastidiosa?

It is a bacterium that lives in the water-carrying vessels of a plant and blocks them. The plant dries out from the extremities inward while its roots sit in wet soil, which is why the classic description is a tree that looks scorched in a season when nothing scorched it. There is no cure once a plant is infected.

The strain found in Mallorca includes subspecies pauca ST53, the same one that devastated olive groves in Puglia. That is the reason the response here is as strict as it is.

Which garden plants are hosts?

The host list is long and it varies by strain, which is why official lists are updated rather than fixed. Treat it as a reason to buy carefully rather than a reason to avoid olives, which would be a strange thing to do on this island.

How does it spread?

Two routes. Sap-sucking insects, mainly spittlebugs, pick the bacterium up from an infected plant and carry it to the next one. And people move it much further and faster than insects do, by transporting infected planting material. That second route is the one regulation targets, with restrictions on moving host plants between the islands and requirements on nursery stock.

Nothing about this is spread through pruning soil or through the ground itself, so the usual garden hygiene advice does not apply in the way people assume. Clean tools between trees anyway, because that is good practice for everything else.

What do the symptoms look like?

• Leaf scorch: browning that starts at the leaf tip and edges while the base still looks green.
• Dieback that begins in the crown or on one branch and spreads, rather than affecting the whole tree evenly.
• Decline over one or two seasons in a mature tree that had no obvious problem before.
• Symptoms concentrated in a group of trees rather than a single specimen.

Drought, root damage and several fungal problems look similar, which is exactly why a suspicion needs testing rather than a diagnosis from a photograph. If you suspect it, report it to the plant health service of the Conselleria rather than pulling the tree out yourself.

What can a garden owner actually do?

Buy from registered nurseries that supply a plant passport, and keep the paperwork. Do not carry olive, almond or vine material between the islands or in from the mainland. Control weeds and long grass under host trees through spring, because that is where the insect vectors breed. And when a tree does have to come out, have it handled by someone who knows the current rules for disposal rather than adding it to a green waste pile.

Does this change what to plant?

Less than you might expect. Olives remain the defining tree of this landscape and gardens are still planted with them. What changes is the sourcing: a cheap olive of uncertain origin bought at the side of a road is a genuinely bad idea, and a properly documented tree from a registered supplier is not. If you want the look with less exposure, carob and Aleppo pine give shade and structure without being on the host list for the strains found here.

How the matching works

We are not plant health inspectors and we do not do the work. What we can do is pass your job to vetted planting companies on Mallorca that source from registered nurseries and know the current rules. Send the job through and they will quote you directly.

Buy the paperwork, not just the tree

A plant passport costs nothing extra and is the one precaution that actually protects a garden. Describe what you want planted and vetted Mallorca companies will quote it with stock they can account for.