A healthy cure for citrus greening

June 2019

For more than ten years, a majority of orange groves in Florida have been afflicted with 'citrus greening'.  The disease has devastated millions of acres of citrus crops throughout America and elsewhere.

The visual symptoms of citrus greening include short internodes (stem length between leaves), tiny leaves, asymmetric chlorosis (loss of green colour in leaves), flowering out of season, and leaf and fruit shedding.

Trees that succumb to this disease produce fruits that are green, misshapen and bitter.  They're unsuitable for sale as fresh fruit or for juice.  Most affected trees die within a few years.

Research into citrus greening has consumed well over $540 million of funding without a single recovered orange or cured tree to show for it.

The assumed cause of citrus greening is a bacterium, Liberibacter, originating in Asia and spread by an insect (Psyllid).  However, presence doesn't indicate cause and effect: it's not been possible to maintain the bacterium in culture to generate experimental proof, and detection of the assumed culprit is based on DNA analysis.

Treatment of citrus greening has focused on the mass spraying of trees with the antibiotic streptomycin, soon to be joined by oxytetracycline to kill the bacterium.  Both these drugs are important in treating human and animal disease, and raise the obvious concern of fostering antibiotic resistance.  Insecticides are applied to kill the insect vector.  Yet, the sick trees aren't getting cured.

A GM virus engineered to deliver a bacteria-killing protein derived from spinach is in the US regulatory pipeline, but its efficacy in the field is unproven.

Some US universities are working on GM citrus trees resistant to citrus greening.  This is a long, slow, expensive road (which might not have an end).

Meanwhile, Frank Dean, product development manager of 'Performance Nutrition' (agriculture and turf division of chemical supply company, LidoChem Inc) noticed that the citrus greening pathology was similar to diseases afflicting crops in the Midwest where corn, soyabeans and tomatoes suddenly develop unexplained problems resulting in crop losses.  Acting on a hunch, Dean demonstrated that every visual sign of citrus greening could be induced with the herbicide glyphosate.

Note.  Glyphosate is used on most GM crops and is used on other crops to prepare them for harvest.  If you're wondering what relevance glyphosate has to orchards, it seems the herbicide is used in lieu of mowing between the trees.  This has come about because, as a water-saving strategy, US orchards have replaced overhead irrigation systems with micro-irrigation in which water is fed directly to the root area from pipes laid along the ground.  This reduces water loss by evaporation but the presence of the pipes prevents mowing.

Dean set about developing the Citrus Greening Recovery Program. This involves bio-degradation of glyphosate residues in the soil, restoring the soil microbial diversity and populations suppressed by glyphosate, and replacing the soil micronutrients which glyphosate makes unavailable to the tree.  The Program also applies several therapeutic doses of three vital amino acids which plants poisoned by glyphosate can't produce: these include a plant hormone precursor needed for healthy root development, and two amino acids which protect trees from diseases and parasites.

A first trial of the Program focused on a 20-acre plot of 3,000 Valencia orange trees.  The outcome was that trees identified as "dead or dying", almost barren of leaves and new shoots, and which had had no harvest for three years before treatment now have a full canopy of leaves, an abundance of fruit and have generated their third harvest.

The conclusion?  It seems that the assumed bacterial infection could be a symptom of a poisoned and malnourished tree, not the cause.  And, as for the insect vector,  it's well-known that when glyphosate is applied, the plant's leaves turn yellow and that the psyllid insect blamed for citrus greening is attracted to yellow leaves.

No money changed hands during Dean's trial.  Inputs were provided free if the grower did the work (and stopped or limited herbicide applications).

The commercial cost of the Citrus Green Recovery Program will be around $500 per acre.  To put this in context, the cost of growing citrus, including the possibly counter-productive agrichemicals, is around $2,000-$3,500 per acre.

It appears there is a cheap, sustainable, scientifically based, proven remedy for the mass poisoning of America's citrus groves.  So, are the authorities rushing to promote it and save their country's citrus fruit industry?

No, they're still pouring money into GMO, pharmaceutical, and pesticidal 'fixes'.  Dean has been called "batsh*t crazy" and his presentation has languished unviewed because it "smelled like a rotting dead fish".

In Dean's assessment, regulators "have painted themselves into a corner": the amount of public funding flowing into research on the supposed bacterium, along with academic assurances of glyphosate's safety make it impossible for them to admit now that a mistake's been made. 
(Regulators are also very shy of treading on biotech industry toes.)

Glyphosate isn't, of course, likely to be the only factor in the ill health of the modern citrus groves: the year-on-year accumulation of multiple pesticides in the soil leads to a build up of debilitating toxic substances in the plant. 


Citrus greening, or the yellow dragon 'huanglongbing', first hit the headlines back in 2010.

Reporting at the time listed a succession of devastating diseases in the groves, the latest of which was citrus greening, and for which the solution was going to be GM orange trees [1].  At the time, we commented on several possible causes, all of which seemed to have a human origin, but the glyphosate-damage option wasn't one of them!

The reactions of the establishment to Dean's work are following an all-too-familiar pattern previously dubbed 'COWDUNG' *[2].  What this achieves is inhibition of discussion and further scientific enquiry, plus a shoring up of the biotech industry, the patents, and the scientific reputations and funding sources. 

*'COWDUNG' - Conventional Wisdom of the Dominant Group

'Saving our oranges' with GM is good PR, but what will happen to our health-promoting oranges when the biotech industry realises citrus greening can be 'cured' with GM glyphosate-tolerant (not antibiotic or insecticidal) citrus trees?

If you want to avoid GM glyphosate-laced oranges in the future, tell your regulators now that there may be a non-GM, non-chemical alternative to 'curing' not only citrus greening but an awful lot of other crop diseases and yield losses.

Most important of all ask for public funds  to be focused on building soil and plant health instead of 'fighting' disease.

[2]  COWDUNG - October 2015

·         Expert says there's a cure for citrus greening - so why is it being ignored?  GM Watch, 11.03.19
CC Photo USDA on Flickr

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