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Witches broom on oleander

Witches broom on oleander

Louise Grabell, Pinal County Master Gardener

There is some bad news out there. Yes, gardeners, beware and be aware! First, ask yourself how many oleander trees/shrubs do we have in SaddleBrooke? A rough guess would be thousands! If you have any variety of oleander on your property and you have one of our technically-capable and knowledgeable “landscapers” taking care of your estate, and even if you don’t, please pay attention. Read to the end, because all of our trees and shrubs are in danger of becoming infected!

Oleanders, in particular, and other woody shrubs and trees are under attack by a disease called witches’ broom. The infected branches show tiny growth of leaves where normal-sized leaves and branches should be. This insidious infection, which may develop unnoticed, is caused by a fungus called Sphaeropsis tumefaciens. Let me quote directly from a letter from Peter Warren, urban agricultural agent for Pima County Cooperative Extension: “To manage this situation, prune branches at least six inches below where symptoms are seen. Look at the cut end of the stem to see if there’s any discoloration from the fungal growth in the wood. If so, prune that branch back further. Make sure to prune during dry times, avoiding periods when rainfall is expected 24 hours before or after pruning. To prevent infection of unaffected plant parts, dip pruning tools in a disinfectant such as 10 percent bleach or rubbing alcohol before using them on another branch or plant. If you have a bucket of bleach handy, with several pairs of pruners on hand, make one cut, then place the pruner in the bucket and retrieve another one from the sanitizing solution. Bleach needs a good 30 seconds to sanitize the pruner surface if this disease is to be killed. Severely-infected plants should be removed and destroyed. No chemical fungicides are available to control this disease.” We have had reports of other shrubs and trees [kumquat], showing this infection.

Here’s the really important message: Our landscapers and their power clippers go from house to house without a worry about spreading this infection, and that’s exactly what they are doing! More and more residents are reporting to your Master Gardeners that their palo verde or oleander or other woody shrub has these strange growths. You can help! First, look for signs of this infection on your property, show it to your landscaper and then show him this article! If he buzz-shaves your infected plant and then goes on to do the same on your neighbor’s property, he is spreading this disease with his clippers and becoming an epidemic vector throughout SaddleBrooke. Only YOU can take the first steps in stopping an onslaught of witches’ broom.

Your Master Gardeners invite you to visit their new website,, for all up-to-date information and events for our community. Garden questions? You can reach our very own Garden Helpline by calling Pat at 407-6459.

Remember, nothing brings more tranquility to the heart than a beautiful garden.