Wednesday, December 16, 2015

Thielaviopsis Trunk Rot in Palms – More Common in 2015

  One of the relatively common ailments seen in palms around Darwin is the death and damage in the stems of multi stem palms.  Think golden cane palm, some Rhapsis palms, sealing wax palms and similar plants common in many gardens.  It does seem to be more common over the past year or so, possibly as a result of less dry season irrigation to palms due to cost issues.

While there can be a few causes, with stress often related to poor irrigation management, a common problem here and also in Florida USA can be plant disease.  Unfortunately a cure is not available – except by removal of the infested plant, burning NOT composting the plant material, and removal and landfill disposal of the remnant stems out of the ground – AND then DO NOT replant a palm in the area.

Typically stress, commonly through lack of dry season water, will rapidly escalate the problem, which could be festering along, and not being noted, as afterall, palms do shed leaves quite readily!  

Water stress is not the cause of the stem dying but it does exacerbate the disease problem, and may act in concert with the disease  leading to severe and rapid escalation of the disease cases.

If you see the palm stem bending and breaking just below the crown shaft area [ the top part where new leaves emerge] , new leaves emerging and appearing brown or dying, cracks in the stem, and at times breaking near the base [ less common in multi stem palms] it might well be this disease.

All that can be done is to remove the infected leaves and dispose of into the landfill [ NOT as greenwaste] or burn them [ preferable], and removing the leftover leafbases and roots, and disposing of them in the same way.

While not highly infectious, it is common to see spread between nearby plants, and removing the source of infection is prudent. Infection via wounds on the palms - at transplanting or even cutting fronds off is seen as a common entry pathway for the disease.

In Florida, this disease and another one [ Ganoderma butt rot or canker] [ also see - ] are a common problem in newly transplanted palms in landscape development, and examples of some of the problems are seen in these reports by Prof Monica Elliott - on Ganoderma and on  Thielaviopsis.

Both diseases are present in palms around the north of Australia.

The photos below are of Thielaviopsis trunk rot photographed in Darwin in late 2015. 

General view - typical of appearance with disease - brown and damaged leaves and stems

common appearance of split palm trunk with Thielaviopsis disease

broken stem below crown shaft in golden cane palm

Commonly seen stem damage on golden cane palms
The disease and pest problem with palms is significant in Florida, with calls to diversify the plants used in landscaping.  However, like here, if in the tropics palms are expected to be seen!

Locally, we need to be aware and wary of the disease issue with palms, and minimise spread.  For example, wait for palm leaves to fall, rather than cutting them off, if possible, and take care with sanitising equipment between plants - for example an antiseptic dip or spray - always a simple, but effective biosecurity measure. 

Watch out for these two widespread palm diseases!

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