 Phoenix Dactylifera and susceptibility to Lethal Yellowing A brief discussion of certain statistical & clinical facts When queried on her position, Dr. Elliott responds that her assertions, presented as facts and with the credibility of the University and her PhD behind her, is made based primarily on peer observations and data. In fact, when repeatedly asked for the clinical or statistical data that was used to formulate her opinion and/or to attend a meeting to discuss her position she repeatedly failed to respond. When the university was subsequently required to respond by a Freedom of information Act filing; it responded with clinical data that I feel failed to support Dr. Elliott’s position and with nearly no statistical analysis at all. What we found was nothing more than opinions of other researchers that were themselves poorly supported by any of the available data and that were up to 40 years old. This is not the kind of science or professionalism we expect from so accredited a researcher or so respected a University and we are disappointed that Dr. Elliott would make such a profound statement with so little data to back it. At least one equally renowned peer of Dr. Elliott’s who spent many years at the University and whom is widely considered to be an expert on palm’s, Dr. Alan W. Meerow, apparently disagrees with her position. Dr. Meerow is a former Professor and Palm & Tropical Ornamentals Specialist at the University of Florida’s Fort Lauderdale Research & Education Center and has authored numerous professional reference books on palms. In 2000 in Dr. Meerow’s “Guide to Landscape Palms” he rated Phoenix Dactylifera as being “Moderately” susceptible to Lethal Yellowing disease. In his 2006 book “Landscape Palms” he updated this rating to “at least slightly to moderately susceptible”. As the positions of these two researchers of equal doctoral credibility differ so widely we felt that a statistical review of the “Medjool” sub variety’s performance during the past 20 years planted in regions where LY is highly prevalent might render a clear picture of actual susceptibility. Granted, our analysis is informal and not necessarily scientifically rendered but the best estimate we can generate of the percentage of the total population of Medjool Date Palms here in Florida that have become diseased with LY or any MLO is less than 0.01%. That’s over a 20 year time span where tens of thousands of Medjools are planted in areas where LY is a common occurrence in Coconut species. For comparative purposes we will look at the Coconut Palm which IFAS and Dr. Elliott have characterized as being equally susceptible to LY as the Medjool. 1. Groundworks has sold in excess of 100,000 Medjool Date palms in Southern Florida since 1990. We estimate that our combined competitors have sold at least 50,000 more in Southern Florida. While this is nowhere near the number of Coconuts that exist in these environs, it is certainly a large enough group of very high profile palms in a fairly concentrated region to compare to Coconuts. In 1971, when LY was identified in Florida, a published survey was conducted and by February 1973 researchers had confirmed approximately 2000 infected palms. By November of that same year the count had reached 20,000 and has grown to the tens of thousands or more since then. In fact, LY is still a commonplace cause of loss of Coconut palms. To date, and during 20 years of the Medjool’s commercial history here in Florida, we know of less than 20 Phoenix Dactylifera that have ever contracted an MLO and many of these are of uncertain lineage and may not even be the Medjool sub variety. This real world reality indicates some minor degree of susceptibility but it most certainly does not support a characterization of “Highly susceptible” and instead makes a case that the Medjool sub variety is far more resistant then most varieties of Cocos Nucifera. 2. From 1979 until 1983 Dr. Howard, a peer of Dr. Elliott’s at the University, conducted a controlled study on P. dactylifera and LY susceptibility using 6 off shoots from five different sub varieties. It is a fact that the single Medjool shoot that survived transplant (four of the shoots they attempted to cultivate did not survive transplant) did not contract LY during the period of the study while other sub varieties did. It is also a fact that this shoot grew into a mature palm and outlived every other one. While this result is considered by the scientific community to be statistically weak because there was only one Medjool to test, this result does not support a characterization of “Highly susceptible”. The published study actually puts forth an opinion of the possibility of varietal differences in susceptibility. This opinion was rendered with respect to the “Halawy” sub variety and it was suggested by researchers that different sub varieties may exhibit different resistance levels. They did not evaluate the Medjool in this light because they only had one to work with but from the stand point of a considered hypothesis, this suggestion seems sensible and appears to have been borne out by the Medjool’s outstanding performance across the past two decades here in South Florida. 3. In that same study it was determined that the known vector for LY, a plant hopper known as Myndus Crudus was attracted to the Coconut palm at a rate that was 10 times that found with any species of Date palm and this was seen to be statistically significant. This may well be one of the reasons that so few true date palms have actually been infected in regions where the loss of Coconuts is commonplace. Here again, the data do not support a characterization of the “Medjool” as being “Highly Susceptible” 4. The study further determined that P. Dactylifera was not a likely host for palm weevils or other insects and that only M. Crudus was found to host on them albeit at very low levels as compared to Coconut species. The information described above was taken directly from the research work that the University and Dr. Elliott finally provided to us under the Freedom of Information Act. In fact, our own observations on hundreds of sites with tens of thousands of Medjools during the past 20 years correspond well to the fact that the Medjool in the study didn’t contract the disease. In our extensive field experience the incidence of LY observed or reported in this sub variety is so rare as to be considered here to be an extremely rare event. We further believe that this display of implied resistance may also display itself when we can statically assess the impact of the newest MLO affecting palms in Florida, Texas Phoenix Palm Decline (TPPD). I have met Dr. Elliott and have found her to be an intelligent, committed researcher. I simply cannot understand why she has apparently ignored the reality of the Medjool sub variety’s proven durability & performance in favor of throwing the university’s weight behind so damaging a characterization of this exceptional palm variety. In my opinion, Dr. Elliott diminishes her professional credibility with this statistically unsupported position on Medjools. From our perspective we know that any declaration stating that Phoenix Dactylifera “Medjool” is highly susceptible to Lethal Yellowing are wholly unsupported by the realities in the field and may well be based on out dated observations of sub varieties other than Medjool. Such assertions are potentially damaging to the credibility of the IFAS research effort as a whole and though we have asked Dr. Elliott and IFAS to clarify their position, so far and to our knowledge, they have not done so. A truly sad state of affairs. Dr. Elliott’s assertions have been potentially damaging to many professionals whom have recommended Medjools for use in Florida landscaping. These include Landscape Architects, municipal officials, state officials and a wide variety of others who have recommended the value & longevity provided by these stately palms. In my opinion, Dr. Elliott, by her statements, has potentially damaged our business and that of others selling these palms and has probably caused fear & consternation with countless palm owners and others considering the use of this variety. In fact, in the environment around us we have seen almost nothing at all that supports Dr. Elliott’s characterization of highly susceptible. We feel very strongly that Dr. Elliott is not recognizing the obvious possibility of varietal differences in Dactylifera (as noted in the early study) with respect to LY susceptibility but we feel that Dr. Meerow may better understand this variable. In my extensive field experience and professional opinion Phoenix Dactylifera “Medjool” is probably slightly susceptible to LY and other MLO’s but only slightly. Our extensive site experience demonstrates the risk to be truly minimal and statically it appears that you would have a better chance of losing a Medjool to a lightning strike. It is important that you actually receive the Medjool sub variety and there is financial motivation for a wholesaler to deliver a lesser performing variety (as has happened numerous times to sites where the Medjool was specified) so requiring a signed, notarized “Certificate of Variety” is prudent & sensible. I believe that Dr. Elliott means well but is relying on out of date observations that are not variety specific while ignoring all of the current evidence just outside her door. Dr. Elliott is a well respected researcher operating in an environment where the information presented is often blindly trusted. We feel that a presentation of that information as fact while concurrently ignoring the statistical realities around her is at best a very poor way to do business. Groundworks includes five years of warranty coverage for losses ascribed to LY or TPPD when we install Medjools. Medjools have shown themselves to be safe for use in Florida, they thrive here and that is the statistically supported fact of the matter. I am not a PhD nor do I claim to be a researcher of Dr. Elliott’s renown but I live in the field and have spent the better part of my adult life with this particular sub variety here in Florida. I stand 100% behind the truth and the truth is that when you invest in certified Medjools, you better plan on them outliving you. George P. Nottingham President Groundworks of Palm Beach County Inc. www.datepalm.com |