FUSARIUM WILT
IN CANARY ISLAND DATE PALMS

Canary Island date palms, Phoenix canariensis, are majestic palms that symbolize San Diego and the Southern Californian life‑style.

However, they are under attack by a fungus known
as fusarium wilt, Fusarium oxysporum f. sp. canariensis.

This fungus is always fatal. It can take a few months to a few years to kill the tree. There is no cure.

The first sign is dying fronds around mid‑canopy, which is above the level where they normally die.

The pinnae or leaflets of the frond die on one side of the rachis or main stem while remaining green on the other side as seen in the left and right photos.

The fronds continue to die higher and
higher as seen in the left and right photos ...

... until the palm eventually dies.

THE CAUSE?

A fungus entering thru the root system or, most commonly, thru pruning cuts.

What can you do to protect your valuable date palm?

It is theorized that the disease is most likely spread from date palm to date palm by pruning with infected tools. What you can do to reduce your palms chances of contracting fusarium wilt is insist that whoever prunes your trees:

Remove only dead fronds and not green or yellow fronds. Most customers believe that by taking as many fronds off as possible they greatly extend the time between prunings.
This is a false assumption.
Do not use chainsaws to cut green or yellow fronds if you do choose to remove them.
Use handsaws for these fronds. The debris that gets caught in the teeth can easily be removed and the saw sterilized between date palms.
A chainsaw is impossible to sterilize.
Insist that the handsaws & spades be sterilized between palms.
Prune your date palms during July, August or September. During this time of year the fresh pruning cuts dry the quickest, reducing the window for spore germination.
Avoid digging in the pneumatode mat (the surface roots around the base of the palm). Damaging these roots opens them up for infection.
Is your tree service company aware of the fusarium wilt danger?

Trimming date palm - San Diego tree trimming

In the left photo, the climber is using a handsaw to cut the fronds. In the right photo, the climber uses a spade to remove the old petiole bases and form the signature “ball” of the Canary Island Date palm. These tools (when sterilized between trees) significantly reduce the chance of spreading fusarium wilt from one tree to the next.