Subject: Re: [SANET-MG] copper side effects on soil fungi

From: Don Lotter <[email-masked]>
Date: Mon, 13 Mar 2006 18:45:55 -0800

I have been interested for a number of years in this subject.  At UCD I 
studied phylloxera damage to grapevine roots in organic and conventionally 
managed vineyards, and found that the damage is much reduced in organic 
vineyards.  Although phylloxera is an insect (not to be confused with 
Phytophthera, a fungus) the damage to the roots comes from soil-borne 
fungal pathogens that enter the phylloxera feeding sites.  Phylloxera, 
which the French had inadvertently brought over to Europe from North 
America with their samples of North American Vitis species, did great 
damage to vineyards in Europe in the 1850s to 1870s, causing the death of 
most.  The V. vinifera (European grape) vines were highly susceptible to 
phylloxera, a North American insect. These vineyards were "organic" except 
for the fact that they used enormous amounts of Bordeaux mix, a 
copper-based compound, for fungal disease control.  Was this the reason why 
these "organic" vineyards were so susceptible to phylloxera damage?  Were 
the beneficial fungi, important in suppressing root pathogen fungi, 
disrupted such that the root pathogens, which may be less susceptible, 
could flourish?  I haven't ever been able to find any data on the levels of 
residual copper in European vineyard soils in the 1950s when they were 
still using Bordeaux mix.
Don Lotter 

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From: Don Lotter <[email-masked]>
Date: Mon, 13 Mar 2006 18:45:55 -0800