A Double Coconut Palm Problem in Illinois?

No, it is not very, often that we receive a palm sample at the U of I Plant Clinic.  We are used to seeing corn and soybeans, as well as spruce, pine, oak, maple, and other tree problems. But, recently, we received a sample of a double coconut palm from a conservatory.

This palm has been declining since at least July (These pictures were taken in July 2011), but recently symptoms have appeared to be serious. This client submitted leaf and root samples to the University of Illinois Plant Clinic.  The double coconut sample submitted to the U of I Plant Clinic was examined for the presence of disease pathogens as well as signs of insects and none were found on the sample submitted.  The root sample that was submitted did not appear to be rotted.  The problem was concluded to be abiotic (no disease). 

I am very, fortunate to have received help from University of Florida– IFAS,  Fort Lauderdale Research and Education Center experts such as Monica L. Elliott, Ph.D. and Timothy Broschat, Ph.D.  After receiving pictures as well as soil/tissue nutrient analysis, they provided the U of I Plant Clinic with the following information:

"The leaf that has already expanded has physiological issues.  In photo “A”, there is a yellow clear line across the entire expanse of leaf about half way down from the leaflet tips – that is an indication of a one time stress during the leaf development – could be cold, could be very mild boron deficiency – hard to say exactly the problem.  These palms are very, very slow growing.  I don’t remember how many leaves they produce a year, but it isn’t very many, so a leaf is in development for months, not days.  The necrotic leaflets on the one side of the expanded leaf are physiological, not pathogenic – but it is difficult to know exactly what caused the damage.  Same for most of the necrotic leaflet tips on the younger, expanded leaf.

Picture A- showing "yellow clear line across the entire expanse of leaf about half way down from the leaflet tips"

The leaf that is emerging in photo “B”:  those spots could very well be pathogenic in origin.  Usually, when I see a halo around a lesion, I suspect pathogen and not physiological.  But, as shown, I can draw a diagonal line through those “spots”, which again is more likely to be indicative of physiological than pathogenic cause.  And, you can observe necrotic leaflet tips, which would be physiological and not pathological." -Monica L. Elliott, Ph.D.

Photo B- "showing a diagonal line of “spots”

"I had responded earlier about the soil and leaf analyses not suggesting anything nutritional, but after seeing these photos, I agree with Monica that this looks physiological.  This is not typical of phytotoxicities, which tend to result in marginal or tip necrosis on all, but the youngest leaf or if systemic, distortion, or tip necrosis of the spear leaf.  This suggests to me a possible temperature problem though it is not typical chilling injury, which affects older leaves more than the newly emerging leaf.  Perhaps cold irrigation water?  These symptoms are similar to something that was common on Dracaena marginata back in the early 1980s, but after years of working on it, we were never able to pinpoint its cause.  We were able to rule out nutritional deficiencies such as boron and calcium, which would be the most likely candidates." - Timothy Broschat, Ph.D.