What’s bugging palms in Southern California?

This Canary palm (Phoenix canariensis) is in the last stages of dying, its crown having already fallen off.

What is more iconic in the Southern California landscape than the exotic palms from all over the world that dot our gardens and give us that far away vacation look we dream of.

From the cool coastal beach strand, to the hot interior deserts, palms play a very important role in our southland gardens.

There are the tall and lanky Washingtonia robusta palms that grow over 80 feet tall and wave on the skyline, to the stately date palm Phoenix dactylifera growing in the Coachella Valley, supplying us with edible and yummy dates.

Palms have become an integral plant in many of the landscapes of today and yesteryear. When large parcels of land were being developed for citrus groves out in Riverside and San Bernardino counties years ago, the Washingtonia fan palm were planted along the property lines to denote the owner’s citrus groves.

There are so many species of palms that adorn our gardens; it is hard to think that many of the stately palms threatened and might be gone in the future due to bugs and diseases.

This medium size Canary palm shows the decline of lower brown fronds leading to the death of the palm.

One bug today that is attacking some palms is known as polyphagous shot hole borer with the fusarium dieback disease aka PSHB.

There are about 10 identified palm species at this time being threatened by this dreaded bug. The insect bores right into the trunks and large palm fronds making tunnels where the female bug lays its eggs and can carry a pathogenic fusarium fungal disease which is the food source for the young larvae inside the palm.

I attended a palm seminar in San Diego where over 100 landscapers, city maintenance managers, farmers, nurserymen and those in the palm industry wanted to learn more about this dreaded bug and it was alarming to hear some of the prognosis for palms.

Some of the palm species that this bug infects are: kentia forsteriana, Phoenix canariensis, brahea armata, Washingtonia filifera (California fan palm), archontophoenix cunninghamiana (King Palm), dypsis plumosa and others.

Sawdust like frass and gumming on the trunk are typical of this borer’s activity. So when inspecting your trees, be on the lookout and be vigilant to keep an eye out for these indicating items.

The large Canary Island palm is really being plagued by another bug, the South American Weevil which gets into the crown of these majestic specimens and eats from within and eventually the huge and heavy pineapple like top tumbles rotting from the inside. The fungi from this weevil infestation is called Pink Rot. Dying palms in the landscape can be a liability if they fall over.

Care of these palms in your landscape is very important with proper horticultural stewardship. A landscape around your home is an investment and you want to protect that investment with proper stewardship and understanding.

This small palm is completely dead.

Early detection and proper removal including disposal of the infected wood can reduce further populations of these bugs and aid in eliminating its spreading.

To help prevent the spreading of the Fusarium fungi, sterilize all pruning tools with 70 percent ethyl alcohol, for pruning tools can spread this fungi from palm to palm if not cleaned properly.

There are also many other ornamental trees in the landscape today that are being challenged by invasive bugs and one must be on the watch with good surveillance.

The past drought cycle has put a lot of trees into a stress mode and when the resistance of these trees starts to break down they become susceptible to what I call opportunistic bugs attacking weak trees.

Roger Boddaert, known as the Tree Man of Fallbrook, be contacted at (760) 728-4297.

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