Pierce’s disease, bacterial canker, citrus greening, crown gall, and many other diseases share a common mechanism. Each is caused by bacterial populations plugging the plant’s vascular tissue, preventing transport of nutrients and water in the plant.
Fields where vascular bacterial diseases become established often have similar environmental and nutritional characteristics. Emerging research describes how these organisms thrive in environments where manganese availability is very low, as a result of chelation or soil oxidation, and where plant sap accumulates elevated ammonium as a result of photorespiration with inadequate carbohydrate reserves.
By understanding the root causes of these diseases we can begin correcting nutrition imbalances and cultural practices to increase resistance and reduce severity. In this webinar, John Kempf describes how to prevent vascular bacterial diseases with organic practices. Watch the video at https://youtu.be/oDumwyNE0CI.
Insects are nature’s garbage collectors,
diseases are her cleanup crew.
Plants have the capacity to be completely
immune to disease, when supported with
the necessary nutrition and microbiome.
There can be two types of immunity:
‘Passive immunity’ where the plant does not
provide the nutrition and/or environment for
the potential pathogen.
‘Active immunity’ where the plant actively
produces immune compounds from the ISR
or SAR pathway.
How can we measure and manage the
nutritional and environmental status within
Eh - pH and Plant Health
Validation of old work by Louis-Claude Vincent (Vincent’s
Bioelectronic: Eh, pH, resistivity as indicator of human health) by
recent researches: virus (alkaline-oxidized), fungi (acidic-
Change in perspective:
● Plants are not necessarily a resource for their bio-aggressors
(pests and diseases): they are so only when they are
imbalanced, especially regarding Eh-pH-EC
● We can, through agricultural practices, cropping systems, and
nutrition management modify these bio-physico-chemical
conditions in soil and plants to make them unfavorable for
● Agro-ecological crop protection, prophylaxy
Pierce's disease Penetration by xylem sucking vector insects:
leafhoppers (Homalodisca), cercopes
Plant response: Thyllose and gums, AND
Location: Xylem only (biofilm that blocks circulation)
Favored by: Heat, pH 6.5 - 6.9
Treatment: Bacteriophage test, natural antibiotics
Virulence: Polygalacturonase (digests pectin)
Prevention: Variety selection, vector control
Eh-pH and Plant Health in Vines
High soil temperatures
Dry soil conditions
Aerobic soils dominated by aerobic bacteria
These oxidizing factors should be
counterbalanced with cultural management
Oxidizing Environmental Factors
Instead, we often add even more oxidizing
factors to the soil environment:
High EC ‘salt’ fertilizers
Principally absorbed in the reduced form.
Generally poorly available in oxidized soils,
or soils dominated by aerobic ‘oxidizing’
The survival, germination, growth, and
variants of pathogens may be influenced by
the amount and form of Nitrogen...
Nitrogen may affect the virulence of a
pathogen by stimulating or inhibiting
enzymes synthesis or activity required for
Datnoff, L. E., Elmer, W. H., Huber, D. M. & Others. Mineral nutrition and plant
disease. (American Phytopathological Society (APS Press), 2007).
Pierce’s Disease (Xylella Fastidiosa)
An application of the strategy is a novel method of control of
citrus variegated chlorosis, caused by Xylella fastidiosa. In this
system a Brachiaria species, a grass that inhibits nitrification, is
grown between the rows of citrus. It is optimally fertilized, mowed
twice a year, under the citrus trees to provide weed control and
nutrients as the mulch mineralizes. With nitrification inhibited, it
provides only NH4 as an N source for the Citrus and increases Mn
uptake by 50% so that the disease is suppressed and overall tree
growth and productivity are enhanced. (Wells et al, 1995, T.
Yamada, Potafos, Piracicaba, Sao Paolo, Brazil personal
1. Datnoff, L. E., Elmer, W. H., Huber, D. M. & Others. Mineral nutrition and plant disease.
(American Phytopathological Society (APS Press), 2007).
The addition of glycine to Agrobacterium
tumefaciens increased the pathogenicity
and virulence of this bacterium.1
Abundant levels of oxidized iron are known
to stimulate Agrobacterium tumefaciens. 2
1. Rubio-Huertos, M. & Beltra, R. [Fixed L-forms of Agro-bacterium tumefaciens obtained by means of
glycocoll]. Microbiol. Esp. 15, 219–230 (1962)
2. Leong, S. A. & Neilands, J. B. Relationship of siderophore-mediated iron assimilation to virulence in
crown gall disease. J. Bacteriol. 147, 482–491 (1981)
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