Identifying Lethal Yellowing Canary Palm

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Prune Canary Island date palm, if necessary, during July, August or September so that cuts dry quickly.
Prune Canary Island date palm, if necessary, during July, August or September so that cuts dry quickly. (Image: Zedcor Wholly Owned/PhotoObjects.net/Getty Images)

A fatal disease affecting the Canary Island date palm (Phoenix canariensis), lethal yellowing is named after the first symptom of infection -- yellowing leaves. A variety of fusarium wilt, lethal yellowing destroys the Canary Island date palm vascular system so that the plant cannot supply water or nutrients to its leaves. Fusarium wilt infects palms through pruning cuts, either directly from tools or through infected sawdust carried on the wind settling on fresh wounds. Canary Island date palm is hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11 and grows 40 to 60 feet tall and 20 to 40 feet wide. Fertile, well-drained soil and full sun provide the best growing conditions and disease resistance.

Things You'll Need

  • Pruning shears or a pruning saw
  • Stiff brush
  • Pine oil

Examine the lower and older leaves on your Canary Island date palm for symptoms of fusarium wilt, which include yellowing followed by browning on one side of fronds, progressing from the base of the leaf to the tip, and brown or black streaks along the stem. The green half of the frond turns yellow and dies later. Dead leaves remain attached to the tree. Symptoms sometimes appear in mid-canopy leaves first.

Brush a pair of pruning shears or a pruning saw with a stiff brush to remove all plant debris. Soak the shears or saw in a solution of one part pine oil and three parts water for 10 minutes to disinfect them.

Cut open a dead Canary Island date palm leaf stem with disinfected pruning shears or saw and examine the interior. Fusarium wilt causes reddish-brown or pinkish discoloration, often on one side of the stem.

Check your Canary Island date palm every month. Fusarium wilt progresses up through the canopy, eventually killing all the leaves and the entire tree. Palms may take three months to five years to die.

Tips & Warnings

  • Fusarium wilt weakens palm immune systems and allows secondary infections to take hold, such as pink rot. Signs of pink rot include rotting leaves, leaf bases and trunks, stunted and distorted new leaves, and pinkish spore masses.
  • To help prevent infection, prune Canary Island date palm as little as possible. Use disinfected pruning shears or a pruning saw, and disinfect tools again after use.
  • Don't use a chainsaw to prune a Canary Island date palm because chainsaws are very difficult to disinfect.
  • Don't dispose of dead palm debris in municipal garden waste collection bins.

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